Growing Plants From Seed You Collect

Growing Plants From Seed You Collect

  • By Susan Martin
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  • September 2017-Vol 3. No.9
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Last year, a friend from high school sent me a packet of seeds she had saved from her zinnias. I had visited her at the height of the summer season in upstate New York and admired the abundance of zinnias in her beautiful garden. When I received her seed packet in the fall, I was excited about sowing the seeds in spring and watching them grow. And they did grow! In return, I’d promised to send her some seeds from my garden. And that pledge brings me to the topic of this article: growing plants from seed you collect.

Why Save Seed

Purchased seed packets are not that expensive for a small-garden home owner, so why go through the effort of collecting and storing seeds? It’s fun to share plants from your garden by sending seeds through the mail to a far-away friend. A lot of gardeners are naturally curious and like to experiment for the joy of learning new things first hand. There’s also just something wondrous about seeing something bloom that was started from a tiny seed saved from your own garden. If you have a large garden area, starting plants from collected seed can also be an economical way of filling the space. Or, perhaps you’ve found a variety of heirloom tomato that you find particularly tasty. Saving seed from that plant is a way to ensure that you will enjoy that variety again next summer. Seed-saving is essential for maintaining unusual or heritage vegetables and flowers. It is also a great way to propagate many native plants.

Let’s Start With Pollination

Before we start to discuss which plants are good seed suppliers, it might be helpful to start very briefly with a reminder of how pollination works. The plant’s male reproductive organ is the stamen. The pistil is the female part. The top of the pistil is called the stigma, which is often sticky. Pollen must be moved from the stamen to the stigma. When pollen from a plant’s stamen is transferred to that same plant’s stigma, it is called self-pollination. Pollen is transferred from one plant to another through either cross-pollination or open-pollination.

Cross-pollination is when one plant pollinates a plant of another variety. Cross-pollination can only occur between varieties, not between different species. If two different varieties of the same species are grown near to each other in the garden, cross-pollination by wind or insects can occur. There will be no effect on this year’s fruit or flower, but the seeds will be affected. If those seeds are planted, the resulting plants won’t be “true-to-type” since they will carry the traits of two varieties. Sometimes, cross-pollinating is used intentionally in the garden to create new varieties. Gardeners produce hybrids through cross-pollinating by hand

Open-pollination is when pollination occurs mainly by insects, birds, and wind. Because there are no restrictions on the flow of pollen between plants, open-pollinated plants are more genetically diverse. As long as pollen is not shared between different varieties within the same species (cross-pollinated), then the seed produced will remain true-to-type year after year. All heirloom varieties are open-pollinated.

Which Seed To Save

Among the more important decisions every gardener makes is whether to choose open-pollinated, heirloom, or hybrid seed varieties. For seed-saving purposes, the most significant distinction among these types is that gardeners should save true-to-type seed from open-pollinated and heirloom varieties, but not seed from hybrids. Let’s look at the differences between heirlooms and hybrids.

Heirloom varieties are open-pollinated. This means that unlike hybrids, seeds you collect will produce plants with characteristics of the parent plant. And that’s key to an heirloom’s survival. The goal is to ensure that all the variety’s genes are transmitted from each generation to the next. Any changes to an heirloom variety are undesirable from a preservation standpoint. Any selection for or against any of the variety’s traits would change the variety’s overall genetic composition. This means that when collecting seeds from heirlooms, you want to take seeds from many different plants of the same variety. You don’t want to select seeds from the strongest, healthiest plants, for example, or the ones with the biggest blooms.

A hybrid plant is a cross between two different species of plants and is identified by an X in the plant name. Hybrids may also occur between different genera, subspecies, varieties and cultivars. Hybridization is a controlled method of pollination in which the pollen of two different species is crossed by human intervention. Hybrids offer the advantage of taking the best qualities of each parent plant. Because they are from a cross, the seeds produced by hybrids will not grow “true,” i.e., seedlings grown from a hybrid could exhibit traits of one or both parent plants or be something totally surprising. Sometimes hybrid seed is sterile and does not grow at all. Keep in mind that a lot of newly introduced perennials are hybrids and their seeds won’t grow true to type. These plants should be propagated by division, not by seed, if you want plants to stay true to the original. Gardeners who use hybrid plant varieties must purchase new seed every year.

Will My Zinnias Look Like Her Zinnias?

Now let’s go back to the original gift of zinnia seeds from my friend’s garden. If her zinnias are heirloom zinnias, that is open-pollinated, the seeds she sent to me will produce zinnias that are true to the parents. But if her zinnias are hybrids, the zinnias I grow could look very different from my friend’s in terms of height, color and size of bloom. Or the seeds could be sterile.

This spring, I planted the gifted zinnia seeds right next to purchased, hybrid zinnia seeds. The gifted zinnias are definitely shorter and the blooms seem to be flatter than the ones from purchased hybrid seed. This is not a reliable “experiment,” however, since I don’t have a picture of my friend’s original zinnias or any detailed information for comparing the two generations of her zinnias. For comparing the gifted zinnias to my purchased-seed zinnias, I would need to make sure that I was comparing the same variety of zinnias, and there are many different varieties. The proximity issue does have implications for collecting next year’s seed.

What Will Happen Next Year?

Because I planted my hybrid zinnias right next to my friend’s seeds, there will certainly be cross-pollination from bees and wind. Some vegetables, such as corn, need to be separated by more than a mile. Some beet varieties require as much as 5 miles, and even that doesn’t guarantee avoiding cross-pollination. If my friend’s zinnias were heirloom, their seeds would now be tainted by cross-pollination and would no longer be true to their underlying characteristics. Next year, I plan to purchase hybrid zinnia seed for one of my gardens and heirloom zinnia seed for another location. The two gardens are about 125 feet apart. This may or may not be enough to keep the heirloom seeds true, but I’ll save some seed from the heirloom variety to plant as an experiment.

Cultivars and Nativars

There is a strong interest in growing native plants to help build up ecosystems that are suited to our local environments. Plant breeders, however, seek to improve even the native species and we now have the option of planting native cultivars or “nativars.”  This means that different varieties of plants have been selected for certain characteristics and bred selectively through cross-pollination by human intervention so as to produce desirable plant characteristics. A plant label that includes part of the name written in single quotes indicates a cultivar.

Open-pollinated, “straight species” native plants are not hybrids, so the seed will remain true. There are, however, many cultivars of native plants which might still be sold under the “native” label. Plants grown from the seed of these cultivars will not be true to type. For example, the straight species Echinacea is purple coneflower, Echinacea purperosa, but many different colored coneflowers have now been developed.  Many cultivars are beautiful and offer characteristics such as better disease resistance or double blooms. Some nativars are not as attractive to pollinators or caterpillars but other nativars are actually more attractive. More studies are being conducted on how straight species natives and native cultivars compare in this respect. In addition, if cultivars are sterile, i.e., not seed-producing, they won’t contribute seed to a natural habitat garden designed to support birds and other wildlife. All of these pros and cons need to be recognized and assessed for inclusion in our own gardens.

Methods of Preparing Seed


Most flowers and herb seeds are prepared by a dry seed method. First, the seeds must be located, which fortunately is pretty obvious, by looking at the flower petals. The petals, whose job is to attract pollinators, are usually in front of the ovary or surrounding it. After the flowers are pollinated, the petals start to wither and fall away and the seed pod or seed head begins to swell with seeds. When you open the pods, the seeds will be inside. Cleome or spider flower, Cleome hassleriana, is an example of a plant with a very obvious seed pod.

Sunflower, Helianthus, Asteraceae family

The Asteraceae family, also called Compositae family, is the largest family of flowering plants. If the flower has a green, yellow, brown, or black “eye” in the center, it is likely a member of the Asteraceae family. This eye is made up of lots of tiny flowers and each flower produces a seed. The seeds develop in the eye and form a seed head. The sunflower is an example of a plant with a very large seed head. Zinnias, rudbeckias, coneflowers, and daisies are all part of this family. Other Asteraceae flowers, such as marigolds, have tight bunches of petals with no eye, but the seeds develop right in the center.


Anise hyssop, Agastache foeniculum, Lamiaceae family

Plants in the Lamiaceae (mint) family may produce many tiny flowers along a stem.  An inflorescence (group of flowers) is a shape in the mint family that resembles a bottle brush. Anise hyssop and basil are examples. The flower head comprises lots of tiny flowers which produce very small seeds.

All of these plants represent dry seed collection, meaning that the seeds are dry when mature. Allow the seed to mature and dry as long as possible on the plant. Seeds should be harvested on a dry day when the pods or husks have dried. After harvesting, store the pods or heads in a dry place and wait until they are thoroughly dry. You can place cut flowers from the Asteraceae and Lamiaceae families stem-side up in large paper bags and allow their pods and seeds to dry out. Shake the bag once in a while to release the seeds. The husks should easily crumble between your hands. Cleaning dry seeds usually involves simply drying and crumbling the pods or husks, then screening or “winnowing” the seeds to separate them from the chaff. Place the seeds and chaff in a bowl and swirl or shake gently. Remove the larger pieces of chaff by hand.

Wet seeds are found in such plants as tomatoes, eggplants, and many squashes. Allow the fruits to fully mature on their plants before harvesting. Tomato seeds can be “fermented” before cleaning. This process can dramatically improve their ability to sprout.

Fermentation removes germination-inhibiting substances from seed coats, makes them more permeable to water, and also helps reduce or control seed-borne diseases (for healthier seedlings). To prepare seeds for fermenting, simply squeeze or scoop the seeds—together with the pulp that surrounds them—into a jar with a little water. There is no need to include more pulp than naturally comes with the seeds. Store this seed/pulp mixture in a warm place (75 to 85º F) for 2 to 4 days. Fermentation will be evidenced by bubbling and/or by the formation of a white mold on the surface of the mixture. Watch closely, as seeds left fermenting too long (especially above 80º F or so) may germinate. Once the seeds start to swell from taking on water, they will have begun their internal process of germination. Once this process starts, the seeds are no longer viable for storage. Odor from the fermentation process is normal.

Now it’s time to clean the seeds. Pour the seeds and pulp into a bowl and add water. Healthy seeds will sink to the bottom of the bowl, while dead seeds and most of the pulp will float. Use your fingers to gently separate the seeds from the pulp. Then, to remove the pulp and dead seeds, carefully pour the extra water with the floating pulp and dead seeds from the bowl. Pour quickly enough for dead seeds and pulp to pour off the top, and slowly enough so that the heavier, good seeds remain safely on the bottom. Repeat this rinsing and pouring process several times.

After cleaning, be sure to dry the seeds thoroughly before storing them. Simply spread the seeds on sheets of paper or paper plates and allow them to air-dry for a few days. Do not use plastic; it could create a breeding ground for mold or fungus.

Storing Seed

After drying, put the seeds in a suitable container, label, and store in a cool place. Suitable containers could include purchased seed packets, envelopes, medicine bottles, baby food jars, or any other containers that seal out moisture.

Many gardeners store seeds in the refrigerator. If you’re short on space, you could store seeds in a garage or cool basement over the winter months and then put them in the refrigerator during the “shoulder” months, the warm months in the fall and early spring. You don’t want the seeds to start germinating from warmth and/or humidity. Different seeds have different life spans. Most dry seeds can be kept for 2 to 4 years in correct storage conditions, i.e., dark, dry conditions below 39ºF.

Sowing Seed

There are four environmental factors which affect seed germination: water, oxygen, light, and temperature. Some seeds will germinate over a wide range of temperatures, whereas others require a narrow range. Generally, 65 to 75°F is best for most plants. Check temperature and light instructions for each type of seed. Once the seeds have germinated, seedlings do best with about 16 hours of sunlight per day. Grow lights will probably dramatically increase the chance of success. When starting seed in the home, supplemental light can be provided by fluorescent fixtures suspended 6 to 12 inches above the seeds. An adequate, continuous supply of water is important to ensure germination and to ensure the health of the seedlings.

If you want to set out seedlings in the spring, you should consult sources about germination times (how long it takes to go from seed to seedling) and when seedlings should be set outside. For example, a snapdragon germinates in 5 to 10 days on average and should be seeded indoors about 10 weeks before the last frost. There is a 50% chance of a last frost occurring on April 7 in our area.  By April 16, the probability drops to 10%, so in order to have seedlings ready to go, you would need to plant snapdragon seeds indoors by about January 20.

Some annuals, such as cleome and zinnia, are particularly good for sowing fresh seed. Rather than collecting and storing seed in the fall and planting in the spring, you can spread the fresh (naturally dried) seed in the fall. Sow fresh seed from your favorite annuals in the fall just by shaking out the dried seed heads and look for seedlings in your garden next spring. Just be sure to note where you sowed so that the seedlings don’t get weeded out during spring clean-up!





  1. Susan Stowe

    Thanks soooo much for including my favorite method of letting them self sow in the fall- just like Mother Nature! This also tells me in the summer that the soil is warm enough to sow purchased zinnia.

    Fellow Master Gardener
    Prince George County, VA

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