What to do after seeds sprout

Starting seeds properly can make or break your entire growing season! Here are some tips that include when to start seeds, which seeds to start indoors, and how to do it correctly.

Why Start Seeds Indoors?

  • Mainly, people start seeds indoors in order to get a jump on the gardening season.
    • In regions with short growing seasons, starting seeds indoors allows you to gain a few precious weeks of growing time, which can really make a difference when frost looms in the fall.
    • In warmer regions, starting seeds indoors can allow you to get in an extra round of crops (especially cool-weather crops) before the heat of summer stifles growth.
  • If you want to grow a lot of plants, buying packs of seeds is usually cheaper than buying individual seedlings from the nursery.
  • While some nursery plants are grown really nicely, others are poor quality. When you plant your own seeds, you have control over the way the baby is raised. This may be especially important if you are an organic gardener.
  • Finally, there isn’t always a great selection of plants at local nurseries. When you plant from seed, you have a much wider choice of varieties, tastes, and textures—and you can experiment with new ones, too!

Which Seeds Should You Start Indoors?

Consult the table below to see which crops are typically started indoors, which are typically started outdoors, and which can be variable. (Note that gardeners in warmer climates will be able to start more crops outdoors than gardeners in colder climates.)

For seed-starting information customized to your location, check out our free online Planting Calendar.

Start Indoors Start Outdoors Variable
Broccoli Beets Beans
Brussels Sprouts Carrots Celery
Cabbage Corn Kale
Cauliflower Garlic Spinach
Eggplant Okra
Lettuce Onions
Peppers Peas
Pumpkins Parsnips
Swiss Chard Potatoes
Tomatoes Radishes
Watermelons Squash/Zucchini
Sweet Potatoes

Before You Start Seeds

  • Be seed-savvy. Obtain seed catalogs from several companies and compare their offering and prices. Some of the regional companies may carry varieties better suited to your area.
  • Make a list of what you’d like to grow. A good rule-of-thumb is to imagine your garden one-quarter the size that it really is. This allows for good spacing practices! See Vegetable Gardening for Beginners for popular beginner vegetables.
  • Prepare for some losses. Though it’s good not to plant too much for your garden space, it’s also good to assume that some of your seeds won’t germinate, or that they will inexplicably die off later. Plant a few extra, just in case.
  • Consider a grow light if you start in late winter. Most veggies need between 6 to 8 hours of direct sun (minimum), so it’s important to have a grow light if you are sowing your vegetable seeds indoors in late winter. A grow light will also keep your seedlings from getting too leggy. Learn more about using grow lights.
  • Team up with a neighbor and share seeds if you have leftovers!
  • Use clean containers. Most seed catalogs offer seedling flats, peat pots, and other growing containers, but egg cartons make good containers for the earliest stages of seed starting, too. Be sure to poke holes in the sides near the bottom of the containers you use in order to allow excess water to drain. Keep in mind that you might need to transplant your seedlings into larger containers at some point before moving them into the garden.
  • Label your containers now! There’s nothing more frustrating than forgetting what you planted, especially when you are testing out different varieties of the same plant.

When to Start Seeds Indoors

  • We’ll get right to the answer: Just check our Planting Calendar, which lists the ideal dates to start your vegetables indoors. We’ve created a customized tool that’s based on your zip code and local frost dates!
  • As a general rule, most annual vegetables should be sown indoors about six weeks before the last frost in your area. See local frost dates.
  • Don’t start your seeds too early, especially tomatoes. Wait until six weeks before your last frost date to start tomato seeds.

How to Start Seeds

  1. Fill clean containers with a moistened potting mix made for seedlings. If you don’t use a pre-made mix, you can make your own by combining peat and equal parts vermiculite and perlite to hold enough water but allow oxygen to flow. Don’t use regular potting soil, as it may not be fine enough for seeds to root through properly. Pre-formed seed starters (such as Jiffy pellets) work well, too.
  2. Plant your seeds at the depth listed on the seed packet. Most seeds can simply be gently pressed into the mixture; you can use the eraser end of a pencil to do so. When choosing which seeds to plant, choose the largest seeds in the packet for the best chance at germination.
  3. Cover containers loosely with plastic or an otherwise clear, waterproof covering to keep them from drying out too quickly. Poke a few holes in the plastic with a toothpick for ventilation; mold growth can occur if containers are not allowed to “breath.”
  4. Water newly started seeds carefully. A pitcher may let the water out too forcefully. A mist sprayer is gentle but can take a long time. We recommend using a meat-basting syringe (aka “turkey baster”), which will dispense the water effectively without causing too much soil disruption.
  5. When seedlings start to appear, remove the plastic covering and move containers to a bright window or under grow lights.
  6. When the seedlings get their second pair of leaves, prepare individual pots filled with a potting mix with plenty of compost. Move the seedlings carefully to the new pots and water well. Keep seedlings out of direct sun for a few days, until they’ve had a chance to establish themselves in their new pots.
  7. As seedlings continue to grow, be sure to water them as needed; while young, they are very susceptible to drying out.

Things to Keep in Mind:

  • You may have to soak, scratch, or chill seeds before planting, as directed on packet.
  • Seeds sprout best at temperatures of 65 to 75°F (18 to 24°C).
  • Find a place in the kitchen where there is natural bottom heat—on top of the refrigerator or near the oven are good spots. (Move the tray if the oven is on, as it may become too hot!)
  • If you keep your seedlings next to a window, remember to rotate the containers every so often to keep the seedlings growing evenly. If you’re using a grow light, remember to raise it a few inches above the tallest seedling every couple of days.


Photo by Sergii Kononenko/

Moving Seedlings Outside (aka “Hardening Off”)

Before transplanting seedlings to your garden, you’ll first need to do something called “hardening off.” This will prepare the seedlings for the harsh realities (i.e., climate) of the outside world!

  1. During their last week indoors, withhold fertilizer and water them less often.
  2. Seven to ten days before transplanting, set the seedlings outdoors in dappled shade that is protected from winds for a few hours each day, gradually increasing their exposure to full sun and windy conditions. This is the hardening-off period.
  3. Keep the soil moist at all times during this period. Dry air and spring breezes can result in rapid transpiration. If possible, transplant on overcast days or in the early morning, when the sun won’t be too harsh.

Watch our video on hardening off for more info:

How to Transplant Seedlings

After the hardening-off period, your seedlings are ready for transplanting. Here are a few tips:

  • Set transplants into loose, well-aerated soil. Such soil should capture and retain moisture, drain well, and allow easy penetration by the seedlings’ roots.
  • Soak the soil around new seedlings immediately after transplanting.
  • Spread a light layer of mulch to reduce soil moisture loss and to control weeds.
  • To ensure the availability of phosphorus in the root zone of new transplants (phosphorus promotes strong root development), mix 2 tablespoons of a 15-30-15 starter fertilizer into a gallon of water (1 tablespoon for vining crops such as melons and cucumbers), and give each seedling a cup of the solution after transplanting.

Learn More About Gardening

Here’s another “quick and easy” method to plant seeds. Also check out our video on the top tips for starting seeds.

Also, consult our library of Growing Guides, which provide planting, care, and harvesting information for all the common vegetables, fruit, and herbs.

Many plants benefit from a head start by sowing indoors during late winter and early spring. For a few crops, notably peppers and tomatoes, this indoor start is an absolute requirement if growing from seed. These tender, tropical plants will be killed outright by frost, and will show immediate signs of distress if exposed to cold spring weather. So the gardener’s strategy is to make an educated guess about when it will be warm enough to transplant them outdoors, and work backwards from that date according to which crop is involved.

Tomatoes, peppers, and many perennial flowers require a good six to eight weeks of indoor growing before even considering peeking outside. But that’s a long time for plants to grow, so here are some strategies to consider while you are waiting to transplant outdoors.

Light

Just about from the time the seeds are first placed into (or onto) the soil, bright overhead light is essential. With insufficiently strong light, seedlings will begin to grow tall and leggy from the very start. The seedlings are stretching their stem tissues, literally straining to get their leaves higher and closer to any light source so they can begin to photosynthesize and produce food for themselves. All seedlings do this, from tomatoes to palm trees.

If sufficient light is supplied, the seedlings have no need to strain and stretch, and they will remain stout and compact, with good colour and overall health. How does one provide sufficient light? Well, every grower has access to different tools. A heated greenhouse would be perfect for most seedlings, but these are expensive and few of us have access to them. So seedling lights are a smart option. Inexpensive T5 fluorescent tubes are available in several sizes. They produce full spectrum light in the frequency plants need for foliar growth. Even with a good double (or multiple) tube set up, it’s recommended that the tubes be kept 10cm (4″) above the tops of the seedlings. That may seem very bright, but one cannot over-apply light in this setting. The Growlight Garden is a self-watering kit with an adjustable hood that can be raised as the seedlings grow. And there lots of other ways to use the lights with adjustable stands. A superb, super-low energy alternative to T5 tubes is the recently developed LED light strips that fit most grow light fixtures.

Heat

Seedling Warmers do an amazing job of speeding up germination. They work with “bottom heat” which gently heats the soil above the ambient room temperature. This stimulates growth and really helps get plants started. But the gardener’s strategy is to keep the seedlings small and compact during this early indoor stage, so the mats should be removed or unplugged once germination occurs. Otherwise, they will continue to encourage fast growth, and the seedlings may become too large for their containers, or take up too much space indoors.

Even for heat-loving tomatoes and peppers, a warm growing space is not required during this nursery stage. Given ample light and a cool environment of around 18°C (64°F), the plants should grow slowly, but steadily, producing the healthiest transplants.

Air Movement

Seedlings will nearly always benefit from some movement of air indoors. This will help reduce excess moisture buildup and the possible mould and mildew problems that result from it. If their leaves and stems are subject to even slight movement, seedlings will develop stronger cell walls and be better prepared for the harsh elements of the great outdoors. If seedlings were started under domes, it’s a good idea to remove the domes after germination so that air can move freely and excess moisture can evaporate from the soil and trays. A very basic table fan is all that is needed to improve air movement for the benefit of seedlings.


Space

There are numerous reasons for encouraging compact growth while waiting to transplant seedlings outdoors. As seedlings grow, they begin to compete with their neighbours for light, and if they are planted together, for nutrients and moisture. The gardener’s strategy here is to prevent unnecessary competition between seedlings. So lots of light and a cool environment will help. But plants continue to grow beneath the soil just as quickly as they do above.

This is a good reason to not fertilize seedlings prior to transplant. Fertilizer produces strong, fast growth, which is not wanted at this early stage. Seeds contain enough food to produce the initial cotyledon or first pair of leaves. These are then used by the plants to produce their own food, through photosynthesis, to allow for the growth of new tissues. Until they need to really go to work at transplant time (and after), the plants need no further nutritional help.

Potting On

The phrase “potting on” describes the gradual transition from seedling tray to small pot, and from small pot to slightly larger pot, as needed, as the seedlings grow. If cold weather persists outdoors, transplanting may be delayed by weeks. And even with the light, space, and environment described above, most seedlings will eventually out-grow their root space.

Most plants are not bothered by potting on, but it should be done with great care not to damage the delicate root system, and without bruising the leaves and stem. Handling seedlings by the root ball is often safest. Refer to specific instructions about each type of plant in question.

Some plants respond very poorly to transplanting, so if they absolutely must be started indoors, it’s a good strategy to use peat, coir, or newspaper pots, or Cow Pots, that can be transplanted, pot and all, into a larger container, or into the garden row. This prevents the seedling from having its roots disturbed, and they will eventually penetrate the pot as it biodegrades in the soil. Soil Blockers are a fantastic alternative for small farms or nurseries, or wherever large numbers of seedlings need to wait for transplanting.


When to Transplant?

The question of when to transplant seedlings is absolutely tied to regionality. The last average frost date in a given region is a very general tool for estimating how many weeks later is appropriate for transplanting. A basic plan can be used by employing our Regional Planting Charts, but it takes careful management to get this right. For peppers, tomatoes, and most tender seedlings, a good rule of thumb is to wait until night time temperatures are steadily at (or above) 10°C 50°F before even contemplating transplants outdoors. It may work earlier with the help of a greenhouse, cloche cover, or cold frame, but that’s another subject.

All seedlings will benefit from hardening off – the process of gently acclimatizing to direct sunlight, cool temperatures, wind, and night/day temperature fluctuations. These can all cause transplant stress, so hardening off is a key step to success.

Summary

I like to think of the indoor seedling stage as an artificial holding area. We want the seedlings to be at their peak possible health once we transplant them. Before that, though, they’re still young. They’re still in school. Only when they actually get transplanted do we put them to work. It’s that key point when they’ll benefit from organic fertilizer to give them the push into the proper growing season. After transplanting is the real time to help these plants accomplish their goal, to mature, and to produce the leaves and fruits that make all this work worth while.

Are you planning on starting your seeds indoors this year?

If you have, but need a little help getting started, take a look at my Ultimate Guide to Seed Starting. In this guide, I show you what tools you need to get started, then walk you through simple step-by-step directions.

If you have started your seeds, then you’ve probably seen them germinate, grow and develop their first set of true leaves.

Now that they’ve reached this stage, what’s next?

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The process of transplanting is defined by moving or replanting a plant from one location to another. In seed starting, plants are frequently moved. The first time we move our plants, is when baby seedlings are transplanted from small-celled seed trays, to larger pots. It happens again when we transplant our seedlings from indoor pots, to outdoor garden beds or containers.

How do you know if your seedlings are ready for transplanting?

For the first time gardener, you may be looking at your seedlings in wonder, not knowing if they are fine to leave in their small cells or needing a move into larger pots?

Even the intermediate-level gardener may wait just a bit too long, thereby stressing the plant. They may be busy with other plantings or even with day-to-day life and miss that perfect window of opportunity to transplant their seedlings. Sometimes that delay in transplanting causes our seedlings to bolt, making the plants long, thin, lanky and starved for nutrition. Transplanting at this late stage, doesn’t always benefit the plant. The timing needs to be right, especially for certain plants.

Signs to look for in your seedlings, telling you they are ready for transplant:

  1. First true leaves have developed; these are the set of leaves, after the first emergent leaves
  2. Leaves are forming a canopy over the soil
  3. Leaves are bright green and healthy-looking
  4. Roots are beginning to emerge from the bottom of the pots
  5. Stems are thickening
  6. Leaves are beginning to exhibit a purple colouration (plant is already beginning to show signs of stress and has a Phosphorous deficiency)
  7. Seed leaves (cotyledon) have turned yellow (the leaves are no longer feeding the plant and the plant is receiving less nutrients from the soil)
  8. Soil needs to be watered daily, due to drying out (the plant is growing and requires more water)

Plants that benefit from transplanting:

Most plants benefit from transplanting into larger containers. These plants include flowers, herbs, brassicas, peppers, tomatoes and much more.

Other plants have delicate roots and are healthier when started in larger containers. These plants include squash, cucumber, zucchini, sunflowers and other large-seeded plants. Plant those seeds in 3.5 inch pots, then transplant the seedlings directly into the garden, after last frost. Do not start them in small cell trays.

How to successfully transplant your seedlings into larger pots?

Here comes the fun part!

Using these tools (listed for your convenience) and following the recommended steps below, you will find that your seedlings will grow stronger and healthier!

Tools Required:

  • Potting Soil
  • Vermiculite
  • 3.5 or 4 inch pots
  • Widger
  • Small Coffee Filters
  • Optional: Large Potting tray

15 Steps to Successfully Transplant Your Seedlings

Transplanting Steps:

  1. I use a potting tray, because I find that it saves time when potting and contains any mess, within the tray. By containing the soil, you are not wasting any that could potentially fall on the floor or table. I absolutely love using a potting tray and I highly recommend it! Simply fill your pots or cell packs over the tray. It’s quick and easy and it’s saved me a ton of time when seeding and transplanting.
  2. Pour your seed starting mix into the large tray. I use the same mix that I used when starting seeds (see Ultimate Guide to Seed Starting). You may add vermiculite to the mix, at a rate of 1/3 vermiculite to seed starting mix. Vermiculite will lighten the texture of the soil and improve drainage. Alternatively, instead of mixing it into the soil, you may add a layer to the top of your pots after transplanting. This approach will help to prevent “damping off”, a disease that lives in wet soil, and causes the stems of seedlings to rot and topple over. Vermiculite is optional.
  3. Line

    Pot lined with a coffee filter

    your 3.5 inch pots with one coffee filter each. The coffee filter prevents soil from spilling out from the bottom of your pots, through the drainage holes.

  4. Fill your pots with seed starting mix and tamp down the soil, with the bottom of another pot; if necessary add more soil, until it fills all but the top 1/2 inch of the pot.
  5. Make a well in the soil, in the centre of the pots with your thumbs, at the same depth as your seedlings.
  6. Water in the well.
  7. Using your widger, insert the wide flat end down the side of the cell, and gently lift up the seedling (soil and all), as though lifting with a shovel. Check out my video on using the widger.
  8. Gently lift up the plant, by the soil, and place it in the well you created.
  9. Using your fingers, gently scoop the surrounding soil up over the seedling soil and push the transplant down into the pot, creating a smooth surface; if needed add more soil.
  10. Optional: Top the soil with a layer of vermiculite.
  11. Water-in well, leaving the pots in the potting tray, to drain off.
  12. Place the pots back on their plant growing tray.
  13. Place the plant tray, filled with pots, back under your grow lights, ensuring to adjust the lights up, to 2-inches above the top of the leaves.
  14. Refer to the Outdoor Planting Calculator, to schedule transplanting your seedlings into the garden.
  15. Begin hardening off your seedlings, approximately 2 weeks prior to transplanting outdoors.

A “well” in the pot soil

Lifting this pepper seedling up, with the wide and flat side of the widger

The seedlings are transplanted successfully

Using this method, you should have no trouble transplanting your seedlings. The widger is a very effective tool (check out my video on using the widger). It allows you to work with seedlings at minimal disturbance. Rather than handling your seedlings by their leaves or stems, which may accidentally cause irreparable damage, this method will keep plant handling down to a minimum.

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Timing is also an important component of successful seedling transplant. Don’t let your seedlings overgrow their cell packs. Keep a close eye on the number of developed leaves and the length of seedling stems. If the plants seem larger than the cells they are growing in, you may be certain that your seedlings are more than ready for larger accommodations.

Good Luck and Happy Gardening!

Here are the tools that I mentioned in the post. Disclaimer: The links to some of these tools are my affiliate links. Meaning, I will get a small commission at no extra cost to you, should you purchase the product through my affiliate link. 397 Shares

Starting Plants From Seed for the Home Gardener

Bulletin 1432 View PDF picture_as_pdf

By Sheri Dorn and Bodie Pennisi
Department of Horticulture

A number of plants, particularly vegetables, annuals, and herbs, can be grown from seed. There are several advantages to propagating plants from seed. Seeds are relatively inexpensive, allowing the home gardener to get many plants for the price of a few transplants. Additionally, selection of transplants or plant materials available for sale can be limited to just a few varieties. Growing plants from seed allows the gardener many choices for the home garden.

The process of growing more plants from seed is known as sexual propagation. Seed or sexual propagation is dependent upon the genetic combination of male and female parts of the flower and is a result of pollination. Pollen from male anthers is combined with the egg in the female ovary, and seed is produced. Seeds described as “open pollinated” result from random pollination that occurs from wind or insect activity. They may appear to look like the parent plant, but they actually have minor differences that are referred to as “variability.”

Just like people, seeds produce plants that resemble the parent but are genetically different. Seeds referred to as “F1 hybrids” are the result of controlled, known crosses of plants that produce the same results each time. These hybrids often have characteristics that make them a unique or superior plant, such as increased vigor, disease resistance, flavor, flower color, or uniform growth. Hybrid seed may cost more than open-pollinated types. If you save the seeds of hybrid plants, the resulting plants may have some similarities to the hybrid parents, but appearance and growth is usually different. Therefore, if you desire the features of the hybrid plant, purchase and plant new seed each year.

Seeds have three main parts. The outer seed coat protects the seed, while the cotyledons or seed leaves provide a food source during germination. The embryo is the young plant. Mature seeds will germinate when exposed to favorable conditions.

Seed Selection

Figure 1. Fungicide-treated seed.

Start with good quality seed from a reliable dealer. Quality seed is true to cultivar/variety name, and does not contain contaminants, such as weed seed, insect casings, soil particles, or plant pulp. Make the best plant selection for the existing growing conditions by researching the many varieties available. Seed can be purchased for a wide variety of plants and characteristics, such as color, size, and growth habit. Many varieties will even be resistant to certain diseases. Choose varieties suitable for your area that will reach maturity before frost, survive heat, and tolerate present growing conditions. It is best to purchase only enough seed for use in the current season. Seed can be stored from year to year, but germination percentage and seedling vigor will decline with age and improper storage conditions. Store excess seed in a cool, dry place. Seeds in paper packages are best stored in containers that can be sealed tightly. A low-humidity environment at 40 degrees F is best for seed storage, such as the crisper drawer of a refrigerator.

Figure 2. Pelleted seed is easier to sow uniformly. (Photo Credit: Bodie Pennisi)

Some seed can be purchased in treated form. One type of treatment is a fungicide coating, which increases the seed’s chance for survival by protecting it from disease organisms in the soil (Figure 1). Small seed may come in a pelleted form, with a coating of clay or other inert material that makes the seeds easier to sow by hand and get a more uniform stand with fewer plants to thin (Figure 2). Legume seed can be treated with nitrogen-fixing bacteria, which help plants draw nitrogen from the air and deposit it in their roots. Similar to hybrid seed, treated seed is also more costly, but can be worth the extra expense.

Reading a Seed Package


Figure 3. Examples of typical seed packages.

Commercial seed packages include a lot of helpful information. Look for the year the seeds were packed, usually printed or stamped on the envelope (will appear as “sell by” or “grown for”). Look for seeds packed for the current season. Additionally, the packet typically indicates how far apart to space seeds within a row, the depth for sowing the seeds, days to germination, and instructions for thinning seedlings. Seed packages can be retained as part of garden records for future reference (Figure 3).

Germination

Germination is the process of the embryo emerging from the seed. It starts with imbibition, or the absorption of water. Germination is heavily influenced by four environmental factors, including water, oxygen, light, and temperature.

Water

Water is critical for the first step in germination. Without water, seeds will remain dormant. The amount of water is critical; too much water causes seeds to rot, and too little water causes embryos to die. Adequate, continuous moisture is essential to germination. Misting seeds with a mist nozzle or a hand-held spray bottle provides light, even, gentle moisture without disrupting seeds. Covering seeds with a thin layer of vermiculite or peat moss helps ensure good seed-to-media contact and helps prevent the embryo from drying out. Keep the humidity high around germinating seeds by covering pots or flats with a clear humidity dome or enclosing plants in clear plastic bags. Remove plastic bags as the seeds germinate and seedlings emerge.

Oxygen

Viable (live) seeds actively respire, releasing carbon dioxide and consuming oxygen. As germination proceeds, respiration increases and more oxygen is needed. Seed-starting media needs to drain well enough to meet this need for oxygen. If the media (i.e., garden soil) is too heavy or too wet, seeds will not have the oxygen they require, and germination may be greatly slowed or stopped (death).

Some seeds require light to germinate, while others require darkness. Some seeds have no preference at all. Look in catalogs and seed packets for specific information for the seeds being grown. If a seed requires light for germination, sow the seeds on the soil surface. If a seed requires darkness, cover it lightly with a layer of fine peat moss or vermiculite.

Temperature

Temperature affects the number of seeds that germinate as well as how fast the seeds germinate. Some seeds have a very specific temperature range for germination, while others will germinate over a broad range of temperatures. Seed packets and catalogs generally list the optimum temperature for germination. A good rule of thumb is 65 to 75 degrees F for germinating most seeds. To monitor soil or media temperature, use a thermometer with its probe in the middle of the container or flat. To raise temperature, use moisture-proof heating mats or cables under flats or containers (following manufacturer’s instructions). Alternately, flats can be placed in warm spots in the home, such as near a radiator, for the germination process. Then move the seedlings to a bright location so they can continue to develop. Monitor temperature and moisture so that embryos and seedlings remain viable. After germination, temperature should be gradually lowered to 65 degrees F.

Materials

Media

Figure 4. Seed-starting media (left) versus growing media (right).

Choose a sterile, soilless potting media without fertilizer to start seeds. Sterile mixes are free of weed seeds and disease organisms. Weeds compete with the germinating seedlings for water and nutrients, and disease organisms can kill seedlings in the early stages of germination. Avoid using garden soil as it is heavy, holds a tremendous amount of water, and often contains weed seeds or disease. A good seed-starting media will have a fine, even texture and be fairly uniform. This will help maintain good contact of seed with media. You do not want a seed-starting media that is lumpy or chunky, especially when sowing small seeds (Figure 4).

There are several sterile, soilless materials from which to choose. Sand, perlite, vermiculite, and peat moss are readily available and can be mixed together to create a media that has good moisture-holding capacity and good drainage. Sphagnum peat moss is often combined with perlite for a seed-starting media. A good recipe for making your own media includes 4 quarts shredded sphagnum peat moss, 4 quarts fine vermiculite, 1 tablespoons of superphosphate, and 2 tablespoons of ground limestone. Mix thoroughly, then wet completely. Leave the soil to drain and do not plant for 5 to 6 days. This allows the lime to react with the peat moss and create a favorable environment for the seedlings.

Containers

Figure 5a. Hydrated peat pellets in a flat with humidity dome.
Figure 5b. Recycled plastic sandwich box.
Figure 5c. Fiber Pots.

Any container can be used for starting seeds as long as it drains, is deep enough for good root development, and is sanitized prior to use (Figures 5a, 5b, and 5c). Plastic inserts, flats, and trays are available for purchase. Rectangular flats and trays are usually 12 to 18 inches long and often come with a clear, fitted dome or cover. You can make your own flats from wood, but they are heavier than plastic flats and are more difficult to sanitize for reuse. Be sure to leave gaps between the slats, or drill holes in the bottom, for drainage. You can fill the flat directly with media, or use an insert or smaller container set into the flat and filled with media. Growing seedlings in individual cells or containers reduces damage to roots and shock to the seedling when later transplanted into the garden or another container.

You can also make your own containers from recycled materials, such as plastic salad boxes and muffin containers, as long as good drainage is provided and there is adequate depth for root development. The clear plastic containers are like mini greenhouses. When the lids are closed, an ideal high-humidity environment is created for germinating seeds. As the seedlings emerge and grow, the lid can be gradually opened and removed. Pots can also be made from recycled newspaper using a can or bottle as a form, or soil blocks can be made with an initial investment in a molding device.

Additionally, seeds can be started in hydrated peat pellets for easy transplant into the garden (Figure 6). For more information on usine peat pellets, view or print the “Starting Plants From Seed using Peat Pellets” information sheet.

Figure 6. Plant growing in a peat pellet.

Sanitation is critical in the germination process. Disease causing fungi can attack seedlings and kill them at this early stage. To reduce chance of fungal attack, use sterile media and sanitized containers. To sanitize used containers, wash to remove any soil or debris and rinse with a solution of one part chlorine bleach to nine parts water. Rinse thoroughly with clean water.

Location

Providing appropriate air and media temperatures as well as adequate moisture and humidity is important to seed germination. Choose a warm location that provides bright, indirect light and good air circulation. For best results, refer to the information on temperature previously mentioned in the section on germination.

Seeding Techniques

Seeds can be sown directly into the container or space where they will grow, or they can be transplanted to another container or space to finish growing. Most seeds are planted at a depth approximately twice their diameter. Very small seeds should be simply pressed gently into the surface of the soil and barely covered.

To raise the humidity for the germinating seeds, the container can be covered with plastic wrap or placed in a plastic bag, but remove the bag as soon as germination occurs.

Once seeds germinate, you will need to provide supplemental light for proper seedling growth. Light stands should position the lights within 2 to 3 inches of the seedlings. As the seedlings grow, raise the lights, but keep them 2 to 3 inches above the seedlings. Set a timer so that the lights are on 16 hours daily. As seedlings grow, raise the lights above the plants. Without supplemental light, plants will be weak and spindly, often stretching toward a window or other light source.

Direct seeding

Not all plants respond well to transplanting, and for some crops, such as beans, transplanting does not offer benefit enough to pursue. Most large-seeded plants, such as corn and pumpkin, and root crops, such as carrots and beets, are best direct-seeded. Sow seeds directly into the container or place where they will grow, following the recommended seeding depth on the package. Species with small seeds can be more challenging to handle. Carefully prepare the seed bed so that it is smooth and even, and pay close attention during germination and initial growth of the seedlings.

Seeds that can be direct sown:

  • Carrot
  • Oak
  • Lima Beans
  • Sunflower
  • Beet Corn
  • Dill
  • Green Beans

Transplanting

Figure 7. Seeds germinating in seed beds for future transplant.

Some seeds are started in a seed bed, transplanted to a secondary container for growth and development, and then transplanted to the container or place where they will grow and finish their life cycle. For example, tomatoes are germinated, transplanted to a flat, grown out for several weeks, and then planted in the garden after last frost. A seed bed may be a small container of seed-starting media, a flat filled with media, or a prepared bed in the garden (though seedlings are at greater risk for insect and disease attack). Seeds can be scattered across the top of the media or sown in rows (Figure 7).

Managing moisture during germination and at the seedling stage can be challenging. You want to keep the media moist so that the embryo does not dry out, but you do not want to overwater. Media that is too wet will cause seeds to rot or seedlings to die. Remember to keep seed-starting media moist to the touch.

While it sounds like a bit of extra work, there are several benefits to germinating seeds in preparation for transplanting. Ultimately, you will end up with the desired number of plants, as opposed to having too few or too many. By germinating in a seed bed and transplanting to the desired flat or container, you do not waste valuable space in your propagation area with containers where seed has not germinated. If you are working with seed whose viability is declining, you can sow extra seed in a seed bed and transplant what actually germinates and is vigorous. This also gives you an indication of when the seed are no longer viable and ready for discard. Growing transplants allows you to make the most of the growing season by having plants ready at the best time for planting outdoors.

Plants that benefit from transplanting:

  • Broccoli
  • Cabbage
  • Tomato
  • Pepper
  • Petunia
  • Pansy
  • Alyssum

Timing

If you are sowing seeds to grow transplants, timing is an important consideration. You want the transplants to be ready for planting in the garden when soil temperatures are appropriate and threat of frost has past. If seeds are started too early, seedlings may be ready for transplant before they can safely be planted outdoors. When timed properly, warm-season plants (i.e., tomatoes, squash, zinnias, and marigolds) are ready to plant outside in the spring garden by the time of last frost. Cool-season plants (i.e., pansies, broccoli, cabbage, and snapdragons) for fall gardens should be planted with enough time to establish and produce before the first frost. Generally, sow seeds 6 to 8 weeks prior to transplant time. For example, if your average last frost date is April 15, sow tomato seeds inside in late-February/early March. For more information, refer to the vegetable planting chart in Vegetable Gardening in Georgia (UGA Extension circular 963).

Thinning Seedlings

Gardeners generally sow more seeds than are desired as a precaution to ensure that the right number of plants is ultimately grown. Especially with tiny seeds, such as pansy or carrot, lots of seeds can end up in a small space. Regardless, seedlings need to be thinned, leaving the remaining plants with enough space between them to grow and develop properly. Even though it can be difficult to remove excess seedlings, crowded plants — plants that are not thinned — are at risk for death from competition for water, light, and nutrients. The spacing information can often be found on the seed packet. Weak or unwanted seedlings can be snipped off with scissors or pinched off at the media level.

Transplanting Seedlings

Figure 8. Transplanting seedlings.

After germination and the development of the first true leaves, the seedlings can be transplanted to a container of choice. Use a pencil or dibble tool to probe under seedling roots and lift gently (Figure 8). Use the same pencil or dibble to create a hole for the seedling in the new container or location. Seedlings should be set at approximately the same depth they were growing in the seedling flat or pot. Avoid planting too deep or too shallow. Never tug seedlings out of a seed bed or transplant container by grabbing the stem. This can result in a crimped stem, which will result in seedling death.

When ready to be transferred to the garden, the small plants will have several sets of leaves and a sturdy root system (Figure 9).

Figure 9. A transplant ready to go in the garden.

After transplanting, water the plants thoroughly but gently. Seedlings can dry out quickly so check them daily, especially if they are on a heat mat or heat cables or under lights. Seedlings dry out faster with additional heat. The first few weeks are most critical because root systems are small and developing.

Begin fertilizing transplants with soluble fertilizer according to label directions for new transplants. Because new seedlings are easily damaged by excess fertilizer, initial applications are often half of the regular rate. Repeat at two-week intervals after transplanting. Never fertilize plants that show signs of moisture stress, such as wilted or gray-green leaves.

Hardening Off

Plants raised in a high humidity, sheltered location need to be prepared prior to planting in drier, harsher conditions, such as outside in the garden. This preparation process is referred to as “hardening off.” One way to prepare plants is to move them outside to a shady location, gradually increasing the amount of sunlight over a period of several days. You can also choose an overcast day to first take the plants outside, bringing the plants back inside after a few hours. Repeat daily, extending the length of time that plants remain outside by an hour, until the plants have acclimated to the brighter, drier outdoor conditions. This transition can also be accomplished by reducing temperatures (to between 45 and 50 degrees F) and reducing water.

The idea is to slow growth and thicken plant cell walls. Start this process one to two weeks prior to planting seedlings in the garden. Take care to transition plants gradually as extreme changes can slow growth to the point of plant death.

Saving Seed

You may want to save seed from your garden plant. These seeds are the result of random pollination and will most likely not produce plants identical to the parents, particularly with hybrid varieties. Be sure that seed collected from the garden is mature and totally dry before storing. Seeds stored with extra plant pulp or plant material that is not completely dry may mold and deteriorate while in storage. Collected seeds usually have a 65-80 percent germination rate, and three-quarters of those seedlings will produce satisfactory plants.

Quick Guide: Directions for Starting Seeds

    1. Select a container, making sure that it is sanitized, will drain, and is deep enough for root growth and development.
    2. Fill the container with moistened, sterile, seed-starting mix and firm the surface.
    3. Check seed package for planting depth.
    1. Make shallow indentations in the media and sow the seed evenly.
    2. Lightly water the surface, and place the container in a warm area (not in direct sunlight).
    3. As seeds germinate, move seedlings to a well-lit area, such as under fluorescent lights.
    1. The cotyledons, or seed leaves will emerge first.
    1. When two or three true leaves emerge, transplant seedlings into flats or small pots filled with moist potting soil. Keep soil evenly moist.
  1. Allow plants to grow several more sets of true leaves. Keep lights 2 to 3 inches above seedlings, adjusting as necessary.
  2. When plants have reached desired size, prepare them for planting in the garden by “hardening off.”
  3. Water the transplants well initially and for several weeks after planting.

Status and Revision History
Unpublished/Removed on Oct 01, 2014
Published on Oct 09, 2014
Published with Full Review on Feb 13, 2018

Starting to Grow

What does the word “germinate” mean?
To germinate means to start to grow. What is a nutrient?
Nutrients are substances that living things need to grow. Nutrients include food, air, water, and vitamins and minerals. Teachers—download lesson plans to use in your classroom!

Where Do Plants Come From?

Plants come from seeds. Each seed contains a tiny plant waiting for the right conditions to germinate, or start to grow.

What Do Seeds Need to Start to Grow?

Seeds wait to germinate until three needs are met: water, correct temperature (warmth), and a good location (such as in soil). During its early stages of growth, the seedling relies upon the food supplies stored with it in the seed until it is large enough for its own leaves to begin making food through photosynthesis. The seedling’s roots push down into the soil to anchor the new plant and to absorb water and minerals from the soil. And its stem with new leaves pushes up toward the light:

The germination stage ends when a shoot emerges from the soil. But the plant is not done growing. It’s just started. Plants need water, warmth, nutrients from the soil, and light to continue to grow.

Disclaimer/Credits Copyright © 2009 Missouri Botanical Garden

Growing New Plants from Cuttings

  • Sweet potato vine (this is the easiest one to try)
  • Clematis vine
  • Honeysuckle vine
  • Hydrangea
  • Pineapple
  • Succulents
  • How to grow shrubs and vines from hardwood cuttings
  • How to grow new plants from softwood cuttings

Sowing Seeds

When you’re just starting out, you will probably purchase seeds. As your garden grows, you may want to start saving seeds for future planting.

  • How to understand the information on seed packets
  • When to start seeds (and when it’s too late)
  • Best soil temperatures for starting seeds
  • Recommended seed starting supplies
  • Favorite seed companies for organic gardeners
  • How to start (plant) seeds (and grow plants)
  • How to make seed tapes for fussy and tiny seeds
  • Household hacks for speeding up indoor seed germination

Growing Fruits & Veggies

  • Tomatoes
    How to grow tomatoes from seed to table
  • Peas
    How to grow peas
  • Raspberries
    How to transplant and grow raspberry canes
  • Strawberries
    How to grow strawberries

Growing Flowers

  • Delphiniums
    How to grow delphiniums
    How to get tricky seeds like delphiniums to germinate (sprout)
    How to get delphiniums to blooms twice in one season
    How to sow delphinium seeds in the fall
  • Foxgloves
    How to grow foxgloves
  • Geraniums
    How to store geraniums for the winter and create new plants from cuttings
  • Hydrangeas
    What type of hydrangea is this? A handy care guide

Grow a Cup of Tea

  • List of 60 plants you can grow for making tea

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