How to pollinate corn?

Hand-Pollination of Corn

Learn how to pollinate corn by hand with this technique.

By Micaela Colley & Jared Zystro

The Seed Garden (Seed Savers Exchange, 2015) by Micaela Colley & Jared Zystro and edited by Lee Buttala & Shanyn Siegel brings together decades of research and hands-on experience to teach both novice gardeners and seasoned horticulturists how to save the seeds of their favorite vegetable varieties.

You can purchase this book from the MOTHER EARTH NEWS store: The Seed Garden.

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Hand-pollination of corn is fairly easy and is com­monly used by seed savers when they are unable to provide a sufficient isolation distance between varieties.

Corn plants are ready to be pollinated when the male inflorescences, called tassels, are fully expanded and the anthers begin to shed pollen. Some preparation for corn hand-pollination, however, must be done before the plants begin to flower. When tassels start showing above the uppermost leaves of a plant’s stalk, it is time to scout for and cover developing ear shoots (female inflorescences). Learning to identify and prop­erly isolate emerging shoots is the most difficult part of the hand-pollination process. Ear shoots develop on the lower part of a corn stalk, in the axil between the main stem and a leaf. As these shoots become visible, they must be covered with special wax coated shoot bags before their hair-like styles, called silks, emerge. Each pollinated silk will produce a single kernel of corn.

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Some manipulation of the plant is necessary to cover the shoot. First, remove the leaf next to the shoot. Some varieties have sizable husk leaves that will elongate with the developing ear; these leaves should be cut back so they will not push the bag off the ear as they continue to grow. Next, make a shallow slice in the collar (the area of leaf that wraps around the main stem) between the ear and the main stem so that the shoot bag can be securely wedged into place. Perform this step with care as the ear can be cut from the plant. Last, place the shoot bag over the immature ear, with the long side of the bag wedged into the slit in the collar. A properly bagged ear is well protected against drifting pollen and can remain covered until it is hand pollinated, but bags should be monitored to ensure that they remain in place.

Hand-pollination takes place during the time when the mature tassels are shedding pollen. Pollen is shed for at least several consecutive days and can be collected on any of these days. Tassel bags should be placed over actively shedding tas­sels in the afternoon. Hold the tassel and top leaf (if necessary) in one hand, slipping the tassel bag over them with the other hand. Fold up one corner of the bottom of the bag at a 45-degree angle and use staples or a paper clip to hold the bag securely around the stem.

That same afternoon, remove the shoot bags and trim the husk tips on each shoot to expose a pencil-wide area of silks in the center. This should be done quickly to limit the duration any devel­oping silks are exposed to airborne pollen, and carefully, as cutting too low will damage the ear shoot. Replace each shoot bag immediately after trimming.

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The next morning, after any dew has evap­orated, gather the corn pollen. Gently bend the bagged tassel over and tap the bag several times to shake the pollen from the anthers into the bag. Keeping the bag tilted so the pollen cannot fall out, slip the bag off the tassel. After all tassel bags have been collected, combine the pollen into a single tassel bag; this pollen mixture will be used to pollinate many ears.

All of the silks in an ear shoot are receptive at the same time. To hand-pollinate an ear of corn, remove the shoot bag and sprinkle the bulked pollen over the silks. Since being trimmed the day before the shoot should have formed a short, even flush of silks that can easily be dusted with small amount (about 1⁄16 teaspoon) of pollen. Work quickly to limit the duration of the silks’ expo­sure to wind-borne pollen. After each pollination, cover the shoot with a tassel bag, securing the bag in place by wrapping the edges of the bag around the stem and stapling the two sides together. Place labels at the base of each pollinated shoot to iden­tify the isolated ears at harvest. The bags can be removed once the silks have dried and the kernels have started to develop.

When the tassels begin to emerge, start scouting for emerging shoots. Corn shoots need to be covered before the silks emerge. Cut back husk leaves, if present. Remove the main leaf next to the shoot so the shoot bag can be slipped into place. Place a shoot bag over the young shoot and secure it by wedging the bag between the shoot and the main stem.
In the afternoon of the day before pollination, place tassel bags over the tassels. Fasten the bottom of the bags tightly around the stem using staples or paper clips. The anthers will shed pollen into the tassel bags the next morning.
On the same afternoon that the tassels are covered, prepare the shoot by cutting the tip of the husk to expose the silks. Immediately replace the shoot bag. In the morning, collect the tassel bags. Quickly remove the shoot bags and transfer pollen onto the silks, which will have grown past where the tip of the shoot was cut the previous day. Immediately after dusting silks with pollen, cover the shoot with a tassel bag to prevent other pollen from reaching the silks. Secure the bag in place by stapling it around the main stem.

For more on seed saving, see our Seed Saving Guide.

Reprinted with permission from The Seed Garden, by Micaela Colley & Jared Zystro, edited by Lee Buttala & Shanyn Siegel and published by Seed Savers Exchange, 2015. Buy this book from our store: The Seed Garden.

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In this Aug. 27, 2013 photo, these ears of sweet-tasting, bi-color corn were grown from seed in containers inside a hobby greenhouse near Langley, Wash. The Burpee’s “On Deck” corn matured in a little more than two months. (AP Photo/Dean Fosdick)

(Dean Fosdick via AP)

One of life’s great treats is biting into corn that was cooked just minutes after it was harvested from your home garden. If you’ve never had the experience of eating fresh sweet corn right out of your yard, now is the time to plant it. Sweet corn is not one of the more commonly planted home garden vegetables, and there are reasons for this.

Although it rarely grows as high as an elephant’s eye, corn plants are fairly large, and they occupy a substantial amount of space in the garden. As a result, many vegetable gardeners don’t plant corn, especially if they have a small garden.

Each plant produces about two ears of corn, so overall production in the space is not as high as it would be for other popular vegetables, such as tomatoes, squash, snap beans or trellised cucumbers. But if you have the space, growing sweet corn is not that much of a challenge, and the results are delicious.

Types to grow

Many early summer vegetables produce over a period of weeks or even months. Corn, on the other hand, is harvested over a relatively short period of time as all of the ears ripen at about the same time. You can get around this by planting cultivars that ripen at different times.

Recommended sweet corn cultivars grouped by how long to harvest include:

Early-maturing: Seneca Horizon

Mid-season: Bonanza, Merit and Funks Sweet G90 (bi-color)

Late-maturing: Silver Queen (white), NK199, Iochief (AAS), Gold Queen and Golden Cross Bantam.

Or, you can plant the same cultivar in succession. Plant seeds in one area and then plant seeds in another area two or three weeks later.

There also are extra sweet corn cultivars. They contain more sugar than normal sweet corn and are able to hold their sugar levels longer after harvest. Based on the genetics involved, they are grouped into two categories: supersweet and sugary enhanced. Recommended supersweet types (which must be isolated from cross pollination with ordinary sweet corn or sugary enhanced) include How Sweet It Is (AAS), Honey-N-Pearl (AAS), XTender 378, 372, 270 BC, Passion, Accelerator, Summer Sweet #8101W, Summer Sweet #7210Y, #8102 BC, Pegasus and Ice Queen.

Recommended sugary enhanced types include Honey Select (AAS), Avalon, Miracle, Argent, Incredible, Bodacious, Precious Gem BC, Ambrosia BC, Sweet Chorus BC, Temptation BC, White Out, Lancelot BC, Silver King and Sweet Ice. (AAS is All-America Selection Winner.)

Planting

Planting corn early — now through mid-April — reduces problems with corn earworms, the leading insect pest of corn in the home garden. When planted this month, corn typically does not require any pesticide sprays.

Although sweet corn does require room, in a 4-by-8-foot raised bed you can grow two rows of corn with the plants in each row spaced 10 inches apart. That’s 20 plants. If they each produce two ears, you have a generous harvest of 40 ears of corn.

Prepare the ground for planting by first removing any weeds or unwanted vegetation. Turn the soil to a depth of a shovel blade (about 8 inches), apply a 2-3 inch layer of compost or composted manure and a general-purpose fertilizer following package directions, and thoroughly mix everything together.

When planting sweet corn, plant two or three seeds every 10 inches in the row, burying them about one-half to 1 inch deep, and water in thoroughly. After the seeds germinate and the plants are 3 to 4 inches tall, thin to one plant per 10 inches.

Sidedress sweet corn plants with a nitrogen containing fertilizer (ammonium nitrate, calcium nitrate, ammonium sulfate) when the plants are about 16 inches high and again when the plants are about 36 inches high. Corn benefits from generous fertilization.

Pollination issues

Many of the commonly grown vegetables are self-pollinating (tomatoes) or rely on insects for crosspollination (cucumbers), but corn is wind pollinated. The male flowers that shed the pollen are located at the top of the plant in the tassel. The female flowers are arranged in rows along the cob enclosed by the shucks. A silk is connected to each of the female flowers, and the other ends of the silks hang outside the shuck. At least one pollen grain must land on each silk to pollinate a female flower, which produces one kernel of corn.

Each kernel of corn is the result of a separate act of pollination. So, it is important to plant corn properly to make sure the wind deposits the pollen on the silks.

For that reason, we plant sweet corn in a block planting of several short rows side by side rather than one or two long rows. By planting in blocks, you allow the pollen to move from one plant to another more surely no matter which way the wind is blowing. Ears that are poorly filled with kernels of corn are generally the result of poor pollination.

Some gardeners take this farther and do hand pollination. This only is practical in the small plantings done in backyard gardens. When the tassels at the top of the plants begin to shed the yellow, powdery pollen, tassels are cut and shaken over the silks.

Harvest and use

The best time to harvest sweet corn is in the early morning while the temperature is low. To determine when regular sweet corn is ready to harvest, first check the silks to see if they have begun to dry and turn brown. Then feel the ear. It should feel firm and full.

Peel back a shuck enough to puncture a few kernels on the ears with your thumbnail. When sweet corn is at its highest quality, the juice from the kernels will be milky white and runny. It is not ready when the juice is clear and watery, and corn is over mature and starchy when the juice inside the kernels is thick and dough-like.

Corn usually matures 18 to 24 days after the tassels appear or 15-20 days after the first silks appear. Watch the corn closely because the quality changes fast with the normal sweet varieties. Refrigerate or cook immediately after harvesting.

Dan Gill is a horticulturist with the LSU AgCenter.

Corn Pollination – How To Hand Pollinate Corn

How wonderful it would be to reap a bounty of corn if all we needed to do was drop the seeds in their little hole and watch them grow. Unfortunately for the home gardener, manual pollination of corn is almost a necessity. Even if your plot of corn is fairly large, learning how to hand pollinate corn can increase your yield and help prevent those sterile stalks that are often found along the edges of your planting. Before you learn about hand pollinating corn, it helps to know a little about the plant itself.

How Corn Pollination Happens

Corn (Zea mays) is actually a member of a family of annual grasses and while it doesn’t produce showy petals, it does have bath male and female flowers on each plant. The male flowers are called the tassel. That’s the part that looks like grass gone to seed that blooms at the top of the stalk. As the tassel ripens, pollen is shed from the center spike downward to the lower fronds. The female parts of the stalk are the ears located at leaf junctions and the female flowers are the silks. Each strand of silk is connected to one kernel of corn.

Pollination occurs when pollen touches the strand of silk. This seems like pollination should be easy. The pollen drifting down from the tassel should pollinate the ears below, right? Wrong! 97 percent of an ear’s pollination comes from other plants, which is why it is important to know when and how to pollinate corn.

Timing for Hand Pollinating Corn

In larger fields, wind takes care of corn pollination. Between air circulation and stalks jostling one another in the wind, there is enough natural agitation to spread the pollen. In smaller garden plots, the gardener takes the place of the wind and the gardener needs to know when to do the job as well as how.

To pollinate corn efficiently, wait until the tassels are fully open and beginning to shed the yellow pollen. This usually begins two to three days before silk emerges from the embryonic ears. As soon as the silk emerges, you’re ready to begin the manual pollination of corn. Pollination will continue for another week under ideal conditions. Most pollen shedding occurs between 9 and 11 am, after the morning dew has dried. Cool, cloudy, or rainy weather can delay or inhibit pollination.

How to Hand Pollinate Corn

Timing is everything. Once you have the when, how to hand pollinate corn is a snap. Literally! Ideally, hand pollinating corn should be done in the morning, but many gardeners have bosses who object to taking time off for such endeavors, so early evening, before dew fall, is your best alternative.

Snap the tassels off a few stalks and use them like feather dusters. Dust over the emerging silks at each ear. You’ll be hand pollinating corn for about a week, so use your judgment as to how many tassels you snap per dusting. Start at the opposite ends of your rows each night to help equalize the distribution. That’s it! You’ve successfully completed your manual pollination of corn.

A relaxing stroll through the garden and a little light wrist action is all it takes. You’ll be surprised at how relaxing hand pollinating corn can be. Sure beats a lot of other garden chores and the rewards will be well worth the time.

Sweet Corn: Pollinating and Fertilizing

Page 5 of 5 of the Sweet Corn Guide

Author: Julie Baka

Example of Bad Pollination

When all the conditions are right (adequate drainage, ample moisture, full sun and good, weed-free soil), a sweet corn plot would seem to have all it needs to produce plump, delicious ears. Two other things may be necessary, though, for a bountiful crop – fertilizer and hand-pollination.

Remember, corn plants need a lot of nitrogen and are pollinated by the wind. All plots likely will benefit by a boost of fertilizer. Hand pollination, however, is only required for very small plots of corn or if just one to three rows of corn are planted. As a wind-pollinated plant, nature does an amazing job of pollinating corn when it is grown in thick plots and large numbers of rows.

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Pollination

How Corn is Pollinated

How Pollen Falls Onto Silks

Hand-pollinating corn is actually quite easy. But, before we get to the do-it-yourself steps, below is a basic explanation of how corn is pollinated.

There are two parts in corn’s pollination process:

  1. the tassels which produce the pollen
  2. the corn silks which transport the pollen down to the individual kernels

Tassels – Each corn tassel produces half a million pollen grains a day, so there are few worries about adequate contact of pollen with the silks. The pollen falls from the tassels by wind to the silks on the ears below. Each plant can self-pollinate. Pollen does not have to go from one plant’s tassel to a different plant’s silk. They also can pollinate from one plant to another. (See our how to choose the best sweet corn article to learn the importance of isolating plants to prevent cross-pollination of different varieties.) See the moisture estimate chart in our corn-planting article if you are unsure if you are over- or under-watering. (link to moisture chart in corn planting article)

Silks – The sticky silks grow 2.5 to 4 centimeters (3/4 to 1 1/2 inches) per day in optimum conditions, starting at the base of the ear. They will continue growing until they are pollinated. When pollen enters the silk tube, it takes about 24 hours to travel to the seed and begin forming a kernel of corn. After fertilization, the silks dry out and turn brown. These silks are your best visual indication of when corn is ready to harvest. They will be brown and mostly dry.

Hand Pollinating Corn

Hand Pollination with a Brush

When the white silks emerge from the husk, it is time to ensure the pollen gets to the ears. The simplest way to do this is to walk through the corn plot twice a day for at least three days. While walking, simply bump and slightly shake each plant so that pollen falls down onto the silks.

To be more precise, place a sack under the tassels and shake the pollen into the sack. Dip a paint brush into the pollen in the sack and then gently paint the pollen onto the silks. Repeat this procedure for 3 days on every ear of corn.

In about 24 hours, you will know if your corn has been pollinated because the silks will begin to dry out and turn from white to brown.

Fertilizer

Fertilizing Sweet Corn for Best Growth

As a fast-growing leafy crop, corn is generally low-maintenance. However, a dose of nitrogen will help raise the level of nutrients in the soil to help create a beneficial environment for corn. For tall healthy stalks, corn enjoys a nitrogen-rich soil environment with enough phosphorus.

Before Planting Corn Seeds

  • Spread a 2-inch layer of compost over the corn plot area. Compost not only adds nitrogen, but also various micronutrients, while improving drainage and enhancing the soil structure.
  • Lightly sprinkle nitrogen fertilizer, organic if available, over the layer of compost. Organic nitrogen supplements may include fish meal, cottonseed meal or blood meal.
  • Using a garden spade, or a grub hoe, mix the compost and fertilizer with the soil until the mixture is about 4 to 6 inches deep.
  • Plant the seeds according to planting instructions for your corn variety and layout.

As the Sprouts Grow

  • Fertilize the plants with a 16-16-8 liquid fertilizer when the corn plants have reached a height of 4 inches, but before it reaches 8 inches tall.
  • Side Dressing with fertilizer

  • Also add a few inches of organic mulch when the corn is 3 or 4 inches tall. Mulch helps conserve water in the soil and helps ensure consistent soil moisture levels that corn plants need. It also attracts earthworms and adds nutrients as the organic matter decomposes and gets incorporated into the soil.
  • Fertilize the plants again when they are about 10 inches tall. This is best done by side-dressing, rather than applying fertilizer directly on the young plants. For this application use a 46-0-0 (all nitrogen) fertilizer product. Spread the nitrogen in a line on the soil surface about 6 inches from the row of corn. Water the corn as usual to help carry the nitrogen down to the root systems.
  • Add nitrogen one last time once the sweet corn ears begin producing silk, using 46-0-0 nitrogen fertilizer according to product application directions.

Understanding Fertilizer Numbers

The numbers on fertilizer containers simply indicate the ratio of nitrogen, phosphorous and potassium (NPK Values) in the product. Unlike general all-purpose fertilizers such as a 15-15-15 product used on lawns, a 16-16-8 fertilizer has a higher level of nitrogen and phosphorus compared to potassium. By comparison, general vegetable garden fertilizers have an NPK value of about 4-3-3.

N – Nitrogen is responsible for producing leaf growth and is the main chemical involved in photosynthesis.

P – Phosphorus (Phosphate) aids in plant maturity, supports the vigorous development of roots, stems, blossoms, and fruits.

K – Potassium (Potash) strengthens the overall plant, providing resistance to disease and reduces plant stress. Aids in early growth, stem strength and improves the color and flavor of fruit.

NOTE: Plants reveal through their overall health, color, size and vitality if they are receiving too much or not enough nutrients. See the nutrient deficiency section below to learn more.

Organic Fertilizers

For those who prefer to enhance their corn’s growth naturally, below is a chart illustrating the nutrients in various natural sources.

  • Bonemeal
    • Contributes Phosphorus 20 – 25%
    • It is very slow acting. It will not burn roots.
  • Compost
    • Organic matter, varying proportion of all nutrients
    • The best all-round organic fertilizer; should also be used with chemical fertilizers
  • Cottonseed meal
    • Nitrogen, 6-9%; Phosphorus 2-3%; Potassium 1.5-2%
    • Low PH, good for acid loving crops
  • Dried blood and tankage
    • Nitrogen, 5-12%; phosphorous, 3-13%
    • One of the best organic sources of nitrogen, aids growth of soil organisms. Quick acting.
  • Fish meal and fish emulsion
    • Nitrogen,6-8%; phosphorous, 13%; potassium, 3-4%, trace element
    • Quick acting.
  • Horn and hoof meal
    • Nitrogen, 7-15%
    • Quick acting.
  • Fresh cow manure
    • Nitrogen, 0.6%; phosphorous, 0.15%; potassium, 0.55%; organic matter
    • Relatively low in nitrogen. Can be used directly on garden with out aging
  • Dried goat or sheep manure
    • Nitrogen, 2.5%; phosphorous, 0.25%; potassium, 1.5%; organic matter
    • Has higher nitrogen than most manures. Needs to be aged or composted at least three months before using on the garden
  • Fresh Horse manure
    • Nitrogen, 0.7; phosphorous, 0.25%, potassium, 0.55%; organic matter
    • Needs composted at least 6 weeks prior to use on the garden to kill seeds.
  • Dried poultry manure
    • Nitrogen, 4.5%; phosphorous, 3.2%; potassium, 1.3%; low in organic matter
    • highest manure in nitrogen level. Do not use directly on plants, as it may burn them.
  • Fresh rabbit manure
    • Nitrogen, 2.4%; phosphorous, 1.4%; potassium, 0.6%; organic matter
    • Needs to be aged or composted at least three months prior to using in the garden
  • Rock phosphate
    • Phosphorous, 24-30%
    • Slow acting, non-burning
  • Dried Seaweed
    • Nitrogen, 1-2%; phosphorous, 0.75%; potassium, 5%; organic matter
    • This is a good soil conditioner because of its hight content of colloids, which retain nutrients
  • Sterilized sewage sludge
    • Nitrogen, 4-6%; phosphorous, 3-4%; trace potassium and elements; organic matter
    • May contain heavy metals that build up in the soil over the years
  • Wood Ashes
    • Phosphorous, 1-2%; potassium, 3-7%
    • An old time standard. Has an alkaline effect on the soil

Corn Deficiency Problems

Nutrient Deficiency Signs

Nitrogen (N)

Nitrogen is necessary for above ground growth of plants and is considered one of the most important nutrients. It is the most important nutrient for corn, a member of the grass family. Nitrogen is used to make proteins that build cell material and plant tissue, promoting growth of the stems and leaves which is especially important for leaf crops such as cabbage, lettuce and spinach. In addition, it is necessary for the function of other essential biochemical agents. Of all the major plant nutrients, Nitrogen is often the most important deciding factor in plant growth and crop yield.

Excess nitrogen can also cause problems by producing excessive vegetation in certain crops where excessive leaf development is detrimental to the crop in reducing the quality of the root, fruit or flower.

Nitrogen Deficiency Symptoms

Nitrogen deficiency causes stunted or slow growth, slender fibrous stems and the classic yellowing of the leaves. Younger leaves remain green longer, because they receive soluble forms of nitrogen transported from the older leaves. This usually causes the yellowing, and in severe cases, dropping of the leaves.

Phosphorous (P)

Phosphorus helps plants transport and assimilate nutrients and is a major building block in all living plants. It is responsible for storing energy. The stored energy allows for transporting nutrients across the cell walls of the plant. Good phosphorus levels ensure crops will reach their full potential for healthy development of fruit, flowers and seeds. Phosphorus helps to build plant vitality and is of special importance in developing strong root systems that ensures better resistance to root rot diseases.

Phosphorous Deficiency Symptoms

Phosphorous deficient plants are usually dwarfed and spindly. The leaves, in contrast to those lacking nitrogen, are often dark green with purple tints. The undersides of leaves are reddish or purple. Leaf veins and margins often turn bronze. Deficiency symptoms occur first in more mature leaves. Fruit development is usually delayed.

Potassium (K)

Potassium enables plants to develop strong, thick stems, healthy roots and large, plentiful fruit. Plants require larger quantities of potassium than any other nutrient. Potassium is associated with movement and retention of water, nutrients and carbohydrates in plant tissue. It stimulates early growth and hastens maturity. Potassium is a key nutrient in the plant’s tolerance to stresses such as cold-hot temperatures, improves resistance to pests and diseases and is essential for the development of fruits, flowers and seeds.

Potassium Deficiency Symptoms

As with nitrogen and phosphorus, potassium is easily redistributed from mature leaves to the younger ones. Therefore deficiency symptoms will appear first in the older leaves. These become ash-gray colored instead of deep green, will look scorched at the edges (marginal chlorosis) and start to crinkle or curl with mottled yellow tips that later turn bronze.

Plants deficient in potassium often develop weak stem and stalks, small fruit and shriveled seeds, along with poor growth and yields. They also become susceptible to disease.

Final Tips for Growing Corn

  • The small offshoots, or suckers, should not be removed from the plants. Generally, the yield will be better if the offshoots are permitted to remain, even though they do not produce ears.
  • Cultivate to kill weeds weekly until the corn plants are tall enough to shade weeds and prevent their growth.
  • Harvest the ears when the silks are brown and a milky juice spurts from the kernels when punctured with a thumbnail. Cook them immediately or prepare to preserve the crop by freezing or canning. Corn’s sweetness and nutrients are lost soon after picking, which varies slightly by variety.

Now that you know pollination and fertilization, go back to our first article in this Guide to make sure you are growing the right variety for your conditions.

Click a page below to read the rest of our Sweet Corn Guide

  • Page 1 How to choose the best sweet corn variety
  • Page 2 How and when to plant for the best results
  • Page 3 Companion plants for nutrients & pest control
  • Page 4 Watering, weeding, and hilling corn
  • Page 5 Pollination & Fertilizer for success

Sources:

  • The Vegetable Encyclopedia and Gardeners Guide by Victor A. Tiedjens; 1943
  • Woman’s Home Companion Garden Book by John C. Wister; 1947
  • Giant Book of Garden Solutions by Jerry Baker; 2003
  • Reader’s Digest Back to Basics: How to Learn and Enjoy Traditional American Skills; 1981
  • BetterVegetableGardening.com: What is NPK Fertilizer

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