By Dan GillLSU AgCenter HorticulturistMany summer-blooming annuals, perennials and vegetables are setting seeds now, and you can harvest the seeds, store them and then grow a new crop of plants for your garden next year. This can be fun, save a little money and allow you to share seeds with gardening friends.
Of course, just because a plant produces seeds doesn’t mean you have to save and plant them. But if you want to grow more of a plant, collecting seeds is one way to do it.
If you decide you’re interested in saving seeds, however, there are a few things to keep in mind.
One of those is that a large number of vegetables and some annual flowers are F1 hybrids. This would have been stated on the seed package or description of the plant. When planted, these seeds produce a generation of vigorous, productive and uniform plants. Without getting too technical, let’s just say the offspring of F1 hybrids do not inherit all of the desirable characteristics or uniformity of the parents, so seeds of F1 hybrids should be purchased each year – rather than trying to save them.
There can also be problems with cross-pollination. This may occur when two or more different cultivars of the same plant are growing in the garden. Insects visit many flowers and can easily transfer pollen from the flowers of one plant to the flowers of another. Seeds that resulted from cross-pollination will produce offspring that blend characteristics of both parents. So if you’re planning to save seeds, always try to isolate cultivars from one another or only plant one cultivar – particularly if you want the resulting plants to closely resemble the plants you collect the seeds from.
Another challenge is that gardeners often don’t know what the seeds look like. That, of course, means they don’t know what to look for when harvesting seed. Experience really is the only way to learn what the seeds of a plant look like (unless you’ve got some left in the package from when you planted or you go out and buy a package of seeds of that plant – to use for comparison). You might think that the seeds would always be obvious, but seeds come in a bewildering array of shapes, colors and sizes. They are not always easy to distinguish.
When collecting your own seeds, you must make sure they are mature before you harvest them. If you harvest seeds that are not fully mature, the embryo inside the seed is not fully formed and cannot finish development once it’s detached from the plant. As a result, the seeds will not be viable and will not come up when planted. Harvesting immature seeds is a common mistake.
Fleshy fruit usually turn from green to a color, like red, yellow or black, when mature. For instance, tomatoes turn red and cucumbers turn yellow when the seeds are mature. Cut open the mature fruit, remove the seeds, clean off any pulp, dry the seeds thoroughly and store them until ready to plant. Seeds are easy to identify in fleshy fruit.
For plants that produce seeds in pods, such as beans, peas, balsam, okra, butterfly weed, cleome and many others, you must allow the pods to stay on the plant until they turn yellow or brown. But you must harvest the pods before they split open and release the seeds.
The most difficult plants to harvest seeds from are those that produce seed heads, such as members of the aster family (Asteraceae) like marigolds, zinnias, black-eyed Susans, coneflowers and daisies. Once again, the seed head must be mature before you cut it to harvest the seeds. Allow the head to turn mostly brown and dry before harvest. Then tear the head apart over a piece of paper to remove the seeds. It helps to know what they look like, but if you can’t distinguish the seeds, save everything that looks like it might be seeds.
Although there are a few instances where you could plant harvested seeds right away, most of the seeds you harvest now and over the next several weeks should be stored and planted next spring or summer. To retain maximum viability, the storage conditions must be cool and dry.
When storing seeds, make sure the seeds are very dry. Next, put the seeds in an envelope labeled with the name of the plant and the date the seeds were collected. Place a tablespoon or two of a desiccant, such as silica gel (available at craft shops for drying flowers) or powdered milk, in the bottom of a sealable container. Put the envelope (or several envelopes) into the container and tightly seal with the lid. To keep the seeds cool, place the container in your refrigerator. Most seeds stored this way will stay viable for a year or more.
The seeds of some plants may require special treatment before they will germinate. This is more commonly necessary for the seeds of trees and shrubs. Seeds from commonly grown annuals, perennials and vegetables generally do not need special treatment to germinate.
Still, if you think you might like to pursue growing different kinds of plants from seeds, especially woody plants, a good reference is helpful. I have found the American Horticulture Society’s Plant Propagation manual, edited by Alan Toogood and published by D. K. Press, to be excellent and very comprehensive.
Get It Growing is a weekly feature on home lawn and garden topics prepared by experts in the LSU AgCenter.
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