- Grow and Save Watermelon Seeds
- How to Grow Watermelons
- How to Save Watermelon Seeds
- Watermelon Planting Calendar
- Recommended Watermelon Varieties
- DIY Watermelon Seed Growing: Saving And Storing Watermelon Seed
- Watermelon Seed Information
- How to Harvest Watermelon Seeds
- What Watermelon Seed Can You Plant?
- Storing Watermelon Seed
Grow and Save Watermelon Seeds
How to Grow Watermelons
Watermelon fruits vary in size from small to quite large ,and in color from dark green to yellow. Although watermelon requires a long growing season, if you start this sprawling plant early enough in the year, you can enjoy its fruits from late summer to early fall. Watermelons, like other vining plants, need plenty of space to grow.
Time of Planting
Watermelon seeds can be direct-sown outside after danger of frost has passed. (Check this frost calendar to determine the average last frost date for your area.)
Plant watermelon into 12-inch-tall hills of soil that are spaced at least 6 feet apart. Sow 6–8 seeds per hill, later thinning to 3–4 plants per hill. Sow watermelon seeds ½-inch deep. Water seeds into the hills after planting.
Time to Germination
Seeds will germinate in 4–12 days.
While it is simple to direct-sow watermelon seeds, you can also start watermelon seedlings indoors 4–6 weeks before the last frost date.
Common Pests and Diseases
Watermelon plants can suffer from anthracnose, cucumber wilt, downy mildew, and powdery mildew. Use row cover to protect plants from pests early in the season.
When and How to Harvest
When harvesting watermelon, cut the stem with a sharp knife or garden tool rather than pulling the plant from the vine. Maturity indicators differ among varieties but include the ground spot turning yellow, the tendril opposite the fruit shriveling, or the rind taking on a dull and waxy appearance. Watermelons are typically ripe when they sound taut and hollow to a tap from the knuckle.
Watermelon is most often enjoyed fresh and cold as a summertime snack. Watermelon rinds can be pickled for a sweet-and-sour treat.
Whole watermelons stay fresh at room temperature—preferably in a cool, dark place to retard further ripening—for up to 10 days under ideal conditions. Storing watermelon in temperatures from 50 to 60 degrees Fahrenheit may extend the fruit’s life to two to three weeks. A watermelon may only last for one week depending on the degree of ripeness when picked.
How to Save Watermelon Seeds
Remember that hand pollination is always an option if the recommended isolation distance of 800 feet (for maintaining varietal purity) is too great for your gardening space.
Recommended Isolation Distance
When saving seeds from watermelon, separate varieties by at least 800 feet or hand pollinate several fruits.
Recommended Population Sizes
A single watermelon plant can produce viable seed. However, to maintain a variety’s diversity over time, save seeds from 5–10 watermelon plants.
Harvest fruits as you would for eating and simply reserve some of the seeds or leave the fruits on the vine until they soften slightly. (This may improve seed quality, but you won’t want to eat the melons at this point.) Seeds inside should be plump and firm.
Cleaning and Processing
Rinse seeds well in a strainer or colander and then spread in a thin layer to dry on coffee filters, paper plates, or old window screens.
Storage and Viability
Store watermelon seeds in a cool, dark, and dry place and always put seeds in an airtight container to keep out moisture and humidity. When stored under these conditions, watermelon seeds can remain viable for 5 years.
Watermelons are a tender, warm-weather crop.
- Sow watermelon seed or set plants directly in the garden in spring 2 weeks after all danger of frost has passed after the soil has warmed to 70°F (21°C).
- Watermelon seed can be started indoors 8 to 6 weeks before plants are set out.
- For the sweetest flavor, watermelons require a long, hot growing season and plenty of room; watermelon vines require 10 to 15 feet of grow room.
Watermelons mature 70 to 100 frost-free days after sowing depending on the variety.
Sowing and Planting Tips:
- Grow watermelons from seeds or seedlings.
- Seed is viable for 4 to 5 years.
- Start watermelon seed indoors 8 to 6 weeks before transplanting seedlings to the garden; set out transplants 2 or more weeks after the last frost in spring.
- Sow seed indoors in peat pots filled with seed starting mix. The indoor temperature should be between 80-90°F (27-32°C) until germination. Grow watermelon seedlings at 75°F (24°C).
- Direct sow watermelons in the garden in spring after all danger of frost has passed and the soil has warmed to 70°F (21°C). In warm-winter regions, sow watermelons in midwinter for harvest in early summer.
- Watermelon seeds will not germinate at a soil temperature below 65°F (18°C).
- Sow seed ½ inch (13 mm) deep.
- Seeds germinate in 3 to 10 days at 80°F (27°C) or warmer.
- Transplant seedlings to the garden after the soil has warmed to at least 70°F (21°C).
- Plant on mounds or hills 12 to 24 inches (30-60 cm) high, space mounds 10 feet apart; vines can easily spread 10 to 15 feet.
- Water to keep the soil from drying.
- Fertilize with fish emulsion or a soluble complete fertilizer at half strength.
- Add aged compost to planting beds in advance of transplanting.
- Watermelons prefer a soil pH range of 7.0 to 8.0.
- Grow watermelons in full sun for best yield.
- Avoid planting watermelons where cucumbers or squash have grown recently.
- Common pest enemies include aphids, cucumber beetles, flea beetles, squash bugs, squash vine borers, slugs, and snails.
- Common diseases include bacterial wilt, fusarium wilt, downy mildew, powdery mildew, cucumber mosaic.
Interplanting: Plant watermelons with bush beans, corn, dill, eggplant, lettuce, cucumbers, squash, and tomatoes.
Container Growing Watermelon: Watermelons are not a good choice for container growing. They require significant room to spread and grow.
Watermelon Planting Calendar
- 8-6 weeks before the last frost in spring: start seed indoors for plants that will be transplanted into a plastic tunnel in 4 weeks.
- 5-4 weeks before the last frost in spring: start seed indoors for seedlings to be transplanted into the garden.
- 4-2 weeks before the last frost in spring: transplant seedlings to a plastic tunnel.
- 1-2 weeks after the last frost in spring: direct sow or transplant seedlings into the garden; minimum soil temperature is 60°F.
Watermelon seed can be started indoors 8 to 6 weeks before plants are set out.
Recommended Watermelon Varieties
- ‘Sugar Baby’ and ‘Sugar Bush’ are small, 8-10 pounds.
- ‘Fiesta’, ‘Regency’, and ‘Sangria’ are 20 to 25 pounds—all are very sweet.
Botanical Name: Citrullus lanatus var. lanatus
Melons are a member of the Cucurbitaceae family; other members cucumbers, squash, watermelon, and pumpkins.
More tips: How to Grow Watermelon.
Lefroy Valley Magazine
Germination is often thought of as the whole process from sowing until the full emergence of the two cotyledon leaves. There are, in fact, two vastly different phases during this period, namely (i) germination and (ii) growth of the radicle and hypocotyl until emergence. If both of these phases are better understood and dealt with separately, less problems would occur during these initial stages of plant production. In this article, seed dormancy, germination, and seedling propagation of watermelon seed will briefly be addressed.
Germination is a complex physiological process with photo-dependency, initiated by water absorption during a period of optimum temperatures. When these three criteria are met, seed dormancy is lifted and the radicle emerges, signalling the end of the germination process.
Sowing Depth in the Field
The size of a seed is a good indication of its optimum sowing depth. When seed is sown too deep, most of the reserves in the endosperm will be used for germination and radicle growth, leaving very little for further development. A good rule of thumb is to sow at a depth of four times the seed width.
The seed absorbs water for its metabolic processes, embryo expansion, and radicle and hypocotyl growth. Because of its size, watermelon seed requires more water during the initial stages of germination than smaller seed varieties do. If germination takes place at relative humidity of 90%, no additional water is required during the first three days after sowing.
Over-watering, especially during cooler periods, will result in a lowered respiration rate and less energy production. Together with seedlings stretching in low light and unhygienic sowing conditions, over-watering also increases the susceptibility of seed and seedlings to water-borne pathogens. Using the water disinfectant Sporekill and incorporating the bio-inoculant
Trichoderma into the seedling growth medium limits the damage caused by these pathogens. The optimal temperature range for successful and uniform germination is a constant 23 – 25°c for the first three days after sowing. However, good results have also been observed at 30°c (day) and 20°c (night).
Water uptake through the seed coat is slower in seedless watermelons, compared to normal watermelon, which means that the seed can easily be suffocated. When there is excess soil moisture, different procedures should be observed.
Procedure for germinating seedless melons in transplant trays:
Prior to sowing, pre-wet a light seedling mix with approx 500ml of water for every 1000gm of mix and pre-heat in a germination room overnight at 30oc.
Sow seed into indentations using warm seedling mix at 1 cm depth and cover lightly with same warm mix or Vermiculite. DO NOT WATER.
Seed coat adherence to cotyledons can be virtually eliminated by placing the seed in the transplant trays pointy end up at 45-90o angle (may not be a practical option for Nursery production).
Place in germination room at 30oc at high humidity and remove when most radicles have emerged.
Move trays to greenhouse and hold at 27oc until emergence is complete. The high temperature assists uniform emergence.
Water only as necessary irrigate sparingly for the first week. DO NOT OVERWATER. Plants should be hardened off by reducing irrigation and transplanted at third true leaf stage.
The greenhouse structure should be sterilized and all sources of possible contamination should be removed before the arrival of the seedling trays. A preventative program against insect virus vectors should also be followed. The optimum air and root-zone temperatures in the structure are 27°c and 19°c, respectively.
Night temperatures below 13°c result in slow growth and cold stress, increasing susceptibility to disease.
A relative humidity of 70% is preferable, but good ventilation throughout the day is even more important. Ventilation is necessary for optimal CO2 levels within the structure and for removing any free-water from the leaf surfaces. High light intensity within the structure ensures sturdy compact seedlings.
Watermelon seed will last 3 – 4 years when kept dry (10 – 15% seed moisture content), and at cool, constant temperatures (14 – 20°c). Seed packaging opened too long before sowing, and frequent and rough handling will lower watermelon seed viability.
In this recurring column, our panel of watermelon experts answer a question posed through our “Ask the Experts” feature in the right hand sidebar. Feel free to ask your own question. All questions get a response and some will be featured here on What About Watermelon.
MALICK FROM TRIPOLI (ALL THE WAY FROM LIBYA!) ASKS: Is it possible to use one black seed from inside a store-bought watermelon to grow your own? If so, what are the instructions to grow my own tasty treat?
Good question, Malick. The short answer is: sort of.
The only problem with growing watermelons using the seeds of a watermelon you bought in a grocery store is that the watermelon you purchased is more than likely a hybrid variety, which is a special cross between two types of watermelon, each contributing their best qualities to create one great-tasting fruit.
You can plant those seeds, and they may grow into a watermelon (though not always), but the result won’t be the same type of watermelon you purchased and enjoyed months ago. It’ll be a smaller, less tasty watermelon – the kind a lot of farmers call “pig melons” because they’re only good for feeding to the pigs.
I’d recommend purchasing watermelon seeds from your local nursery or gardening store. If possible, buy the open pollinated heirloom variety, which will yield fruit with seeds that you can plant the next year.
If you’re up for a challenge, or just curious, and decide to use seeds from a store-bought watermelon (or are using seeds from an open pollinated heirloom watermelon), you’ll need to dry the seeds before you plant them. Oh, and make sure the watermelon hasn’t been chilled, because the cold temperature will damage the seeds. To dry your seeds, place them on a towel or some newspaper in a sunny spot (a window sill will do) for about a week. Once they’re dry, you can plant them!
Of course, actually growing a watermelon is a whole other question and process in itself. It requires a lot of attention, water and sunlight, but the reward for all your hard work is definitely worth it. Do some research online for tips on growing your own watermelon. To get you started, this website has a brief overview of the process. Good luck, and let me know how it turns out!
UPDATE: Malick e-mailed me back about two weeks later with the following exciting news and photo below:
I just thought I would inform you that the seeds I planted HAVE grown in to baby watermelon plants but it hasn’t been quite long enough for them to grow watermelons yet. Thanks a lot for all the information you gave me!
DIY Watermelon Seed Growing: Saving And Storing Watermelon Seed
Have you ever had a watermelon that was so tasty you wished every melon you would eat in the future was just as juicy and sweet? Maybe you have given some thought to harvesting seeds from watermelons and growing your own.
Watermelon Seed Information
Watermelons (Citrullus lanatus) are a member of the family Cucurbitaceae originally hailing from southern Africa. The fruit is actually a berry (botanically referred to as a pepo) which has a thick rind or exocarp and a fleshy center. Although not in the genus Cucumis, watermelon is loosely considered a type of melon.
The flesh of watermelon is usually recognized as ruby red, but can be pink, orange, yellow or white. The seeds are small and black or slightly mottled black/brown in color. There are between 300-500 seeds in a watermelon, depending upon the size of course. Although usually discarded, the seeds are edible and delicious when roasted. They are also highly nutritious and high in fat as well. One cup of watermelon seeds has over 600 calories.
How to Harvest Watermelon Seeds
It’s not always possible to save seeds from all types of produce, but doing so is an act of autonomy — teaches about plant biology and is just plain entertaining, or is at least for this garden geek. In the case of watermelon, it’s a bit of work separating the seeds from the flesh, but doable.
It is simple, although a bit time consuming, to harvest watermelon seeds for growing. The melon should be allowed to ripen well past its edibility prior to harvesting, since seeds do not continue to ripen once the melon is removed from the vine. Pick the watermelon after the tendril nearest to it has completely dried and withered. Store the melon in a cool, dry area for an additional three weeks. Don’t chill the watermelon as this will damage the seeds.
Once the watermelon has cured, it’s time to remove the seeds. Cut open the melon and scoop the seeds out, flesh and all. Pour the “guts” into a large bowl and fill it with water. Healthy seed sinks to the bottom and dead (not viable) will float along with the majority of the pulp. Remove the “floaters” and pulp. Pour the viable seeds into a colander and rinse off any clinging pulp and drain. Allow the seeds to dry on a towel or newspaper in a sunny area for a week or so.
What Watermelon Seed Can You Plant?
Keep in mind that harvesting watermelon seeds for growing may result in a slightly different melon the next year; it depends on whether the melon is a hybrid or not. Watermelons purchased from the grocers are more than likely hybrid varieties. A hybrid is a cross between two types of watermelon having been selected and contributing their best qualities to the new hybrid. If you try to use these hybrid seeds, you may get a plant that produces fruit with only one of these qualities — an inferior version of the parent.
Whether you decide to throw caution to the wind and use seeds from the supermarket melon or are using those from an open pollinated heirloom variety, be aware that watermelons need plenty of space. Melons rely on pollinators, which mean that they are more likely to cross-pollinate with a possible disastrous result, so keep different types of watermelons at least a ½ mile from each other.
Storing Watermelon Seed
Make sure the seeds are completely dry before storing watermelon seed. Any moisture left in them and you are likely to find mildewed seed when it comes time to use it. Seeds, when properly prepared, can be stored for five or more years in a sealed jar or plastic bag.
Know When the Watermelon is Ripe
Watermelons are a warm-season crop that can takes months to achieve the ripe stage where the fruits are ready for harvesting. Depending on the cultivar, watermelons can be ready for picking in around 60 days, or take over 100.
Check the seed packet where it lists “days to harvest” to get an approximate idea of when you can expect your particular watermelon to ripen. Saving seeds from a ripe watermelon offers the best germination success.
Although the days to harvest gives a good idea of when you can expect to pick a ripe melon, there are other signs that signify your watermelon is ripe and ready for picking. Remember, once harvested, an unripe watermelon won’t continue to ripen any further. Once you determine the watermelon has achieved the prime stage of ripeness, simply cut the melon off the vine.
Signs a watermelon is ready for harvesting include:
- The curly tendrils on the stem where attached to the watermelon change from light green to brown and become dry.
- The watermelon’s appearance changes from shiny to dull.
- You can’t penetrate the outer skin with a thumbnail.
- The bottom portion of the melon that touched the ground changes from green to yellowish.
- The heavier the watermelon, the riper it is.
Expert Gardener Tips: Although an old wives tale says you can determine if a watermelon is ripe by “thumping” it, don’t rely on this test or you can end up disappointed. Some varieties of watermelons won’t have a dull thud and you can end up with an overripe and mushy melon.
Steps for Saving Watermelon Seeds
Of course, the first step in saving watermelon seeds is cutting open the melon, sinking your teeth into the sweet and juicy flesh and enjoying a bit of summer heaven. Nothing is quite as refreshing on a hot summer day like biting into a slice of cold, thirst-quenching watermelon.
While you are enjoying your summer treat, simply spit the seeds onto a napkin or cup. Once you finish your succulent treat, you then can prepare the seeds for saving.
- Wash the watermelon seeds to remove any flesh clinging to them.
- Spread the clean seeds out on a paper towel and allow them to completely dry for a day or two. Don’t store seeds that are still moist or they can mold, which shortens their life and affects germination.
- Place the dry seeds in an airtight container like a plastic one with a tight-fitting lid or plastic bag.
- Note on the container the watermelon’s cultivar name, expected days to harvest and the date the seeds were saved.
- Store the container in a cool, dry area until planting time the following spring.
Expert Gardener Tip: Properly stored watermelon seeds should remain viable for approximately four years. The most important thing when it comes to saving watermelon seeds is keeping them dry and cool.
Why have we been spitting out watermelon seeds all this time? They’ve got more protein than eggs and taste delicious, silly us.
Maybe it is a sign of our lucky abundance that most of us don’t know (or didn’t until recently) that we can (and should) eat watermelon seeds. Why didn’t we remember that seeds are nutritional powerhouses? Why didn’t we think of eating those from the watermelon before, rather than turning them into mouth-born projectiles to be aimed at pesky siblings?
Well, better late than never.
My lesson came from seeing a package of sprouted watermelon seeds at the supermarket. Having already discovered the wonder of exploring the palatability of other novel-to-me seeds (like butternut squash), I thought, “huh, of course.” And I got to reading and experimenting.
Seeds really are wonder foods. They are tiny little fuel packs waiting to sprout forth and turn into a plant – and because of that, they are loaded with all the good things, like protein, vitamins and minerals, fiber and importantly, healthy unsaturated fats.
Watermelon seeds are no different, despite the carefree fruit they produce. With 8 grams of protein per ounce, they have more than a large egg! They are also a great source of healthy fats, iron, magnesium, zinc, and other nutrients.
Alas, they shouldn’t be eaten straight from the fruit – they are at their tastiest and most nutritious after sprouting. Sprouting also removes the black shell, to reveal surprising creamy seeds like those pictured below.
© Room’s Studio
Sprouting takes a few days, but it’s worth it. The Kitchn describes how to do it here; and the Vegetarian Times has an even more comprehensive tutorial. The gist of it is, you just need to soak them so that they begin to sprout; the seeds then emerge from the shells, and then you dry them in the oven or dehydrator.
Or, you can take a shortcut:
HOW TO ROAST WATERMELON SEEDS
If you don’t have the patience, can also roast your seeds; though they won’t have quite the same nutritional punch, they are still awesome. Rinse and dry your seeds, toss in olive oil and a little salt, and bake on a baking sheet at 325F for 10 to 15 minutes. They will still have their shell, so crack and eat them like you would sunflower seeds.