Harvesting & Storing Seeds

By Steven W. Woodmansee, FNPS President

Perhaps one of the biggest challenges to growing new native plant species is obtaining seeds and germplasm for them. Germplasm is a term used to describe any plant material used in propagation. It could be seeds, cuttings, air layers, or tissue (root or otherwise).  By and large, the plant nursery industry often prefers cuttings or tissue culture as they present the easiest/cheapest way to mass produce plants, as well as preserve certain plant characteristics. Seeds are generally the preferred method ecologically, as each seed will present a unique set of genetic material thereby assuring genetic diversity within a species and preventing things like artificial genetic drift (i.e. plants will no longer be selected for survivability), disease susceptibility, inbreeding, etc.

Not all plants are the same when it comes to harvesting, storing, & germinating seed/fruit. First things first, when harvesting wet or pulpy fruit, in general it is best to clean remove the flesh and have clean seeds. If you don’t have time to clean the fruit right away, store it in a lidless bucket with some water for less than 24 hours (Figure 1). If you need more time place them on some netting in the sun so that the flesh may dry out. It is okay if ants eat the flesh off the fruits for you. Then you can soak the fruit in a bucket for 24 hours or less and clean them. You may need to cover the bucket/netting to prevent the birds from eating all your harvest. For plants with very small seed (e.g. Corkystem passionflower, Ficus spp., or blueberries), one can crush them on newspaper and let it dry out over the afternoon. Once dry, it is not necessary to painstakingly separate the seed from the dried pulp when storing them. Some plants, such as native Crotons & Heliotropes, have seed in fruit which is a capsule that dehisce (fancy botanical jargon for opening up), one can collect these fruit and place them in a paper bag in a cool dry place, under an air conditioner vent, or even in the sun (Figure 2). The capsules will pop open and eject the seeds, so it is important to keep it tightly closed. For some plants, such as many wildflowers, it is unnecessary to clean them, and they can go straight into storage containers.

Once seeds are clean, store them in paper bags, paper envelopes or glassine envelopes like the ones from the Post Office (Figure 3). If they are in a container be sure and have it ventilated at the top by placing a hole in the lid of the jar/can. Store all seed containers in a cool dry place that is well ventilated. Heat, especially moist heat, is the biggest threat to seed storage. Although there may be some exceptions such as cold storage, seeds should never be kept in sealed containers or plastic bags of any sort or they may have fungal issues and rot. For some species, the older the seed, the less likely it will germinate. 

Some other tips on seed storing:

• Temperate plant species generally have seed that store well over time, and they may need a period of cold in order to germinate (e.g. Dahoon Holly, Oaks, & blueberries).

• Tropical plant species from moist habitats (such as hardwood hammocks) and palms generally do not have seed that store well over time (e.g. Lignum vitae, capers, & strongbacks).

• Large seed, wildflower seed, and legume seed (members of the pea family) often have seed that may store for many years (e.g. Jamaican dogwood, milk peas, skyblue clustervine, & tickseed).

FNPS members John Lawson of Silent Native Nursery and Rob Campbell of Signature Palms contributed to this article.

Image sources
pepper seed extraction and soaking
paper bag drying 
paper seed envelopes
glassine envelopes



Formatted and illustrated by Laurie Sheldon.