Harvest seed pods of the hyacinth bean and similar plants when the pods are brown. (Photo by Dan Gill, LSU AgCenter)

It is easy to collect the large seeds of nasturtium. (Photo by Dan Gill, LSU AgCenter)

For Release On 09/25/15

By Dan Gill
LSU AgCenter Horticulturist

Many summer-blooming annuals, perennials and vegetables are setting seeds now. You can harvest some of 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 seed with gardening friends.

Understand that just because a plant produces seeds you are under no obligation to plant them. If you want to grow more of a plant, collecting seeds one way to do it. There are, however, a few things to keep in mind.

A large number of vegetables and some annual flowers are F₁ hybrids. This is 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, suffice it to say that the offspring of F₁ hybrids do not inherit all of the desirable characteristics or uniformity of the parents. Seeds of F₁ hybrids should be purchased new each year.

Cross-pollination also may be a problem. This may occur when two or more different varieties 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 result from cross-pollination will produce offspring that blend characteristics of both parents. So always try to isolate varieties from one another or only plant one variety if you are planning to save the seeds, 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 and so don’t know what to look for when harvesting the seed. The only way to learn what the seeds of a particular plant look like is through experience – or by buying a package of seeds of that plant. You might think that the seeds would always be obvious, but seeds come in a bewildering array of shapes, colors and sizes, and they are not always easy to distinguish.

Harvesting immature seeds is a common mistake. 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 detached from the plant. As a result, the seeds will not be viable and will not come up when planted.

Fleshy fruits usually turn from green to a color, like red, yellow or black, when mature. For instance, tomatoes turn red and cucumbers turn yellow. To save the seeds, cut open the mature fruit, remove the seeds, clean off any pulp, dry the seeds thoroughly and store them until you’re 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 harvest 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 seedhead 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 likely.

Although in a few instances you could plant harvested seeds right away, most of the seeds you harvest now and over the next several weeks will be stored and planted next spring or summer. To retain maximum viability, the storage conditions must be cool and dry.

First, make sure the seeds are very dry. Next, put the seeds in an envelope labeled with their name and the date 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) into the container, and tightly seal it 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” edited by Alan Toogood, published by D. K. Press, to be excellent and very comprehensive.

Rick Bogren