Seed Saving Part 2: Selecting Seeds and Controlling Pollination
November 20, 2019
Our food security begins and ends with seeds. Heirloom and organic seeds, in particular, are under threat with the decrease in seed diversity. More growers are needed to develop and grow vegetables and continue sharing the skills and knowledge required for seed conservation. There is an urgent necessity for the age-old tradition of seed saving, with growers playing the role of privileged seed stewards, to expand into backyards and farms everywhere. With climate conditions everchanging, it’s vital that all gardeners, growers, and farmers play a part in preserving seeds in their own patch to protect biodiversity and resilience in food crops.
While some farmers save seed on-farm, home gardeners and small horticultural growers are also getting involved. Seed saving groups have popped up all over the world with small gatherings of dedicated growers meeting regularly to swap, save, and process seeds they’ve grown and collected. While the steps are relatively simple, there is an ‘art’ to seed selection and plant pollination before seeds can be harvested, processed, and stored.
Seed saving is an investment, but one that returns rich rewards over time. Food sovereignty is our greatest wealth and seeds are valuable stock. Preserving our best plants for future generations by careful seed selection and plant breeding yields an asset of great value.
So how does one determine which plant seeds to start with as breeding ‘stock’?
What Seeds to Save
When so many plants provide a wealth of free seeds, it’s a waste not to harvest this potential bounty. However, not all seeds are equally valuable or suitable.
Seeds to Avoid
Hybrid (and F1) varieties are the result of breeding techniques that usually involve two highly inbred parent varieties that are genetically different, but the same plant species. These plants have been cultivated with specific characteristics such as high yield or size, but if you save seeds from them, they won’t grow true-to-type. The results will be very unpredictable.
F1 Hybrids have to be created every time by crossing the same parents. They are bred for uniformity and ‘hybrid vigor’ – a blend of qualities that enable the plant to grow more successfully than either of its parents.
Hybrid plants do not give reliable results for seed saving. They will be sterile, or the next generation may vary widely in their characteristics, uniformity, vigor, and maturity. These types of seeds suit farmers who require uniform ripening and consistently sized produce to meet market deadlines and make harvesting and production much easier. However, they typically need high inputs of fertilizers and pesticides to achieve such standardized production.
GM (Genetically modified) seeds are the result of laboratory processes where genes from the DNA of one species (such as a herbicide) are extracted and artificially inserted into the genes of an unrelated plant. Techniques involving genetic modification differ from traditional genetics using methods such as selective breeding, tissue cultures, and hybridization that assist nature but do not bypass natural laws. There are many documented studies on the health risks of GM crops, as well as ethical and environmental concerns about GM seeds and plants. From a seed saving perspective, they are not suitable. GM seeds are patented so they cannot be legally reproduced without paying royalties.
So, if you avoid hybrid and GM seeds, what types of seeds are suitable for seed saving?
Best Seeds to Save
Open-pollinated seeds. These seeds are pollinated naturally by insects, birds, animals, wind, and moisture. They will produce plants that are ‘true-to-type’ or be clones of the parent. Open-pollinated seeds come from stable, non-hybrid varieties of plants resulting from pollination between the same or genetically similar parents. They are also known as ‘true’ or ‘pure-bred seeds’. The parent plants produce matching seeds – similar to identical siblings! All the plant family looks and behave the same.
To avoid chemically treated seeds when growing food crops, it’s ideal to source untreated, certified organic or heirloom varieties. Certified organic seeds mean they have not just been grown organically (without any chemicals) but originated from certified organic seeds.
Heirloom or heritage seeds are non-hybrid varieties that have been passed down from one generation to the next but are not usually used in modern agriculture. These are sometimes the weird and wonderful varieties we don’t see anymore in the supermarket and are generally open-pollinated varieties. Heirlooms are preserved for their high-value characteristics including flavor, size, color, aroma, resilience to pest or disease and high yields.
Local varieties are cultivars that have been grown in one region over a long period. Sometimes, you can track down the history of regional varieties through seed companies that pride themselves on supporting local seed savers and have records of the origins, or seed saving organizations.
From personal experience, I’ve noticed that when I first sow seeds from another region, the plants aren’t necessarily at their optimum in the first year. They’re acclimatizing! However, after one season in my soil and microclimate, they have adapted to retain a new level of resilience. Sometimes, I’ve noticed the plant grows taller or beans have more flowers and pods, or they are more drought-resistant the second year. Over time, this natural selection process encourages greater diversity and adaptation to the new environmental conditions with each generation, until the plants are strong and at their best.
If you’re going to save seeds, it’s worth revising basic botany skills regarding plant pollination. Most vegetables and herbs have complete flowers with both the male and female parts in the same flower. Some complete flowers, like lettuce, tomato, peas, and beans are self-pollinated. Because the male and female parts are so close to each other in tightly closed flowers, the slightest movement from wind, insects, or birds causes the pollen to transfer.
Some self-pollinating varieties that will ‘inbreed’ naturally to a degree including lettuces, capsicum, chili, and tomatoes.
Other types of complete flowers are open, and they need their pollen to be transferred by bees, insects, humans, or wind. This is called open-pollination because these plants are incomplete and have imperfect flowers or male and female parts on separate plants, requiring cross-pollination. You can also hand pollinate many crops, including pumpkins, zucchinis, cucumbers, corn, and spinach.
Some plants are quite promiscuous and will cross-pollinate freely with neighboring varieties! Vegetables in the Brassica oleracea or cabbage family are a good example. If cabbages and cauliflower are going to seed in close proximity at the same time, the result may be a cauliflower-cabbage cross!
Most Plants Require Isolation for Purity
Many vegetables and flowers must be kept isolated from similar varieties of the same species during flowering to avoid cross-pollinating and gene mixing. Seeds saved from plants that have been cross-pollinated by other varieties do not reproduce true-to-type. Instead, cross-pollinated seeds produce plants with an unpredictable mix of traits from both varieties.
Plan your garden to give plants the room they need to avoid crossing. Even if you are not saving seed from a particular variety, it may still pollinate other plants that you are growing for seed. A little time spent laying out your garden before planting can save time and effort later – and can make the difference between producing pure seeds or crossed ones. There are seed saving charts available with ideal distances and methods of isolation so you can choose a method that suits what you want to grow. It’s best to start with easy seeds like lettuce or radish and progress to more complicated varieties.
3 Ways to Keep Seeds Pure
You can isolate these crops by:
- Time. Stagger planting and saving seeds, so varieties don’t overlap;
- Physical barriers. Cover the seed heads with a bag or cage with fine net or mesh to prevent insects carrying the pollen from one plant to the next;
- Sufficient distance. Grow plants apart so pollen or insects carrying pollen won’t travel between them.
Annuals, Biennials, and Perennials
It’s vital to know what kind of plant you are saving seed from. They are divided into three types:
- Annuals are plants that complete their life cycle or produce seed and die, in one growing season. For example, lettuce, beans, peas, pumpkins, cucumbers, melons, basil, coriander, broccoli, and annual radishes.
- Biennials require two seasons to complete their life cycle and then produce seed and die. These include cabbages, onions, leeks, beetroot, parsnips, celery, parsley, and carrots.
- Perennials live for a minimum of three years, but some can live for decades. They usually can produce seeds and not die. Edible perennials include many herbs, such as oregano, thyme, and rosemary, as well as berries, rhubarb, artichoke, asparagus, tomatoes, eggplant, and chillis. Seed saving is not as imperative for these plants as it is for annuals.
Days to harvest
One factor to consider is the number of days of warm weather required to produce harvestable seed. Short maturity crops like coriander can take only 100 days, whereas it could take bean pods 4-5 months before they are mature and ready. Cool climate growers may need to experiment to determine which vegetables and herbs can produce sufficient seeds. Using a greenhouse and sowing early may help extend the season.
Know where to find seeds on the plant:
- Seed heads – flowers develop on a stem and then seeds form. e.g. lettuce, parsley, basil, carrot, dill, silverbeet, beetroot, coriander, parsnip, and fennel.
- Pods – flowers develop then small elongated pods form. e.g. rocket, mustard, peas, beans, broccoli, tatsoi, and cabbage.
- Fruits – seeds are contained inside the skin. e.g. tomatoes, capsicums, chilies, cucumbers, pumpkin, eggplant, or in the case of strawberries on the fruit.
You will need to make some tough decisions about which plants have ideal attributes. Also, be prepared to sometimes sacrifice your crop harvest to save seed. You need to think about the number of plants you’re going to grow carefully. The size of the gene pool impacts how many plants you dedicate for seed collection versus harvesting to eat. While you can technically get away with saving a small quantity of seed from one or two plants for some varieties, collecting seed from multiple plants will encourage maximum diversity. Even in the same garden, soil, moisture, pH, and microclimate conditions can differ significantly, and the more variability, the better the seed quality can be.
Just like we weed our garden, you also need to remove poor performers that are weak or have undesirable plant traits; a practice called roguing. Avoid weak, pest-attacked, drought-stressed plants or any that bolt to seed quickly.
Saving seeds from specimens with ideal characteristics requires careful observation. Use tags early during the growing season to identify plants for saving with their variety names, dates and other criteria you are saving them for.
- Choose healthy, robust disease-free plants to avoid passing disease pathogens onto new generations.
- Look for characteristics you do want, including superior flavor, color, size, and high yielding varieties. Save seeds from plants that bear early, are slow to bolt to seed, are drought-hardy, or disease-resistant.
Early Seed Formation
Once you’ve chosen your ideal plant for saving seed, nurture it so it will be in the best health possible to produce a new generation of plants and seeds. During the reproduction phase of a plant’s life cycle, it has a greater need for water, nutrients, and protection until it is fully mature.
The health of your seeds begins with the plants that produce them. The time when your plants are first beginning to flower is especially crucial to final seed viability. Plants should be strong, healthy, and minimally stressed during early seed formation and development. Give seed-producing plants plenty of water, light, and fertilizer early in their lives, so that they are healthy when flowering commences.
When some plants mature, they send up a stem. With the additional weight of the flowers and seeds, they may fall over, so staking may be necessary for support to avoid damage.
Watering During Seed Formation
Sufficient moisture at flowering time is essential to successful pollen development and flower set. Too little water during flower initiation and early seed development lowers seed yields, and can even hurt the health and vigor of your mature seeds.
However, dry conditions are preferable during the latter stages of seed maturation. This is when seeds have formed and are drying in preparation for dormancy. Dry conditions are most favorable to the final vigor, viability, and storage life of your finished seeds.
If mature seeds get wet from watering or rain, this slows their natural process of preparing for dormancy, extending the time during which their stored food reserves must be used for respiration. This lowers the seeds’ final dry weight and shortens their storage life.
Repeated wetting and drying of mature seeds on the plant delays dormancy excessively, and can also damage seeds due to alternate swelling and shrinking of seed tissues. If they are left on the plant during rainy periods, seeds may even mold or mildew in their pods or husks. For these reasons, it is best to harvest your seeds and bring them inside for final drying as soon as they are fully mature and dry— especially if rains threaten.
With a little planning and careful selection, your time and effort invested in saving seeds will pay off. Just like a nest egg for a rainy day, starting a seed ‘bank’ of your own can be a profitable way to secure your future food security.
For more in Garden Culture’s Seed Saving series:
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- Garden Strategies to Cope with Drought – Part 2 - January 15, 2020
- Garden Strategies to Cope with Drought – Part 1 - January 13, 2020
- Seed Saving Part 2: Selecting Seeds and Controlling Pollination - November 20, 2019