Almost all native plants can be propagated from seeds, although it can be time-consuming and, with some species, undependable. However, using seeds is a valuable propagation method because it reduces the likelihood of injuring the parent plant, minimizes your impact on natural settings, and makes it possible to grow a large number of seedlings.
Most seeds can be planted as soon as they are ripe, or dried and stored for later use. The best time to collect seeds is when they are mature. Most seeds begin to ripen in early summer and can be harvested in the fall.
As the seeds or fruits mature, check them frequently for ripeness seeds are ripe when they have turned dark and hard, while berries are ripe when they turn their ripe color(s). Try to collect shortly before they reach full maturity: you don't want to wait too long and lose all the seeds or berries to animals or the wind. When collecting seed capsules or cones, look to see whether there still are seeds inside. Make a note of the dates you find particular species of seed ripening so that in future years you will know when to collect them.
It is important to consider genetic diversity when propagating plants from seed. Collect seeds from several different plants to ensure genetic diversity preferably plants at least 100 feet apart. Collect from areas that are similar to your planting site and, if possible, from within the same watershed. These strategies will help ensure that plant genes match their growing environment for the best chance of successful propagation.
1. Collecting Seeds
Collect seeds in paper bags, as plastic bags will trap moisture and rot the seed. However, plastic bags do work well for moister berries, such as cascara and salmonberry. Be sure to write the plant species and the collection date and location on the bags.
Most fruits or seed capsules can be picked directly off the plant. You may need to use a ladder to reach them on trees and taller shrubs. Don't cut off branches to get the seeds!
Cones should be collected before they open, usually after they start to turn brown. To remove cones from conifers, pick easy-to-reach cones and use a ladder or long pruners to reach cones in upper branches. Don't cut off branches to get the cones, and take care not to damage the tree.
The seed heads of rushes, sedges, and bulrushes should be picked just before they are ripe, and placed in a paper bag to dry. As they dry, the seed capsules will burst open and the seed will fall to the bottom of the bag. If not planted immediately, these seeds should be stored in moist sand at about 40° F.
2. Extracting the Seeds
Most seeds need to be separated from their fruits before planting. The exceptions to this rule are conifer seeds (once they are out of their cone they do not need to be separated from their "wing") and acorns.
Separate the seed by hand-crushing the capsules, and then sift through a strainer or shake in a bag so the seed falls to the bottom.
Separate pairs of maple seeds, if still attached. They can be planted with the "helicopter blade" still attached. They don't store well, so sow immediately.
Place fruits in a jar of warm water and crush the pulp with your fingers. Let the jar sit in a warm place until it stinks: this will make separating the pulp from the seeds much easier. The pulp can then be removed from many fruits by hands.
For fruit with many seeds (e.g., berries), place some of the fermented fruit in a blender or food processor, add water, and then run the machine just long enough to mash the fruit (to avoid ruining the seeds, use a plastic blade and a slow speed). Allow the seeds to settle, then pour off most of the water and any floating pulp or seed ("floaters" are not good seed). If you are going to plant the seeds right away, they do not need to be completely clean, and can be strained out at this point.
However, if you wish to dry and store the seeds, they will need to be fairly clean. After pouring off the water with the floating pulp and bad seed, add more water, blend, and pour off excess water again. Repeat process until the water runs fairly clear. Strain the good seeds out with an appropriately-sized screen or sieve (very small seeds can be strained through pantyhose), and dry them.
Cones must be dried to remove the seeds. To preserve the seeds and prevent molding, spread out the cones on a screen or sheet in a warm place with good air circulation immediately after collecting them. Turn them every few days to prevent molding. When the cones have opened fully (a few days to a couple weeks), the seeds can be extracted. Cones can also be dried in an oven set below 100° F (drying times can be found under the species descriptions of the particular plant in the native plant database), but they should first be allowed to dry at room temperature for 3-7 days. If your oven will not keep such a low temperature, turn it off and use a light bulb on an extension cord to heat the oven.
Once the cones have opened, dump them in a large paper bag, roll the top shut, and shake the bag vigorously for at least 5-10 minutes, until you think your arm is going to fall off! When you remove the cones, the seeds will be lying at the bottom of the bag. If you are not sure you have recovered all the seeds, put the cones back on the drying screen, wait a few more days, and try again.
An alternative to shaking is to place the cones in a heavy cloth bag (not your best bag, since you will get pitch on its interior). Tightly tie the neck of the bag shut with strong rope or cord, place the bag in a heavy- duty clothes dryer, and turn it on without heat the seeds will drop from the cones to the bottom of the bag.
3. Drying and Storing Seeds
Native plant seeds perform best when planted soon after collecting. Try to plan your projects so you can sow the seed on-site or in beds or trays shortly after collecting and cleaning it.
If you are not going to use the seeds immediately, spread them thinly on screens in a warm, well-ventilated area that is not in the sun. DO NOT dry seeds in an oven. If you use a food dehydrator, turn off most of the heating elements, and don't let the temperature exceed 100° F. Turn the seeds over every other day to avoid damage from insects, fungi, or moisture. Berry seeds are sufficiently dry if, when you try to crush them between your fingernails they feel totally hard.
You can separate dried seeds from chaff or debris by using different-sized screens, but don't spend too much time trying to obtain pure seeds a little debris is usually okay. However, be sure to throw out broken, shrivelled, moldy, and bug-eaten seeds.
Place the dried seeds in a labelled, airtight container, and store in the coolest place in the refrigerator or in a cool, dry place. However, DON'T expose them to freezing temperatures (the ideal storage temperature is 34°-38° F) unless there are instructions to the contrary in the species description found at the plant database.
4. Breaking Seed Dormancy
Seed dormancy is a state of delayed growth, and is a seed's way of ensuring it does not germinate (sprout) until conditions are suitable (usually in the spring). In the Pacific Northwest, the dormancy of almost all native seeds is naturally broken by exposure to cold and moisture (winter), followed by lengthening amounts of daylight (spring).
If you sow the seeds in the fall, either directly on-site or in containers that are kept outside over the winter, you won't have to do anything special to break the seeds' dormancy the weather will do it for you. However, if you want the seeds to germinate without over-wintering outside (say, by storing them and then planting them in the spring), you will need to artificially recreate the conditions that break the seeds' dormancy. The seeds of a few species require additional factors to break their dormancy, such as the heat from a fire or passing through a bird's digestive system, and you will need to artificially recreate these conditions if you want the seeds of these species to germinate.
Three of the easier methods for breaking seed dormancy are described below. Which method should be used with which species can be determined by consulting the particular plant in the plant database.
COLD, MOIST STRATIFICATION (mimics over-wintering): Combine one part water with four parts sand, perlite, or other absorbent, sterile material. Add seeds to the mixture, place in a sealable polyethylene bag (small ziplock ® bags work well), and label the bag. Put it in the refrigerator (NOT the freezer). Once a week the bag should be opened (lets fresh air in), checked for adequate moisture and seed germination, resealed, and turned over (prevents compaction). The chilling time needed may vary from 3-18 weeks, depending on the species. However, unless noted otherwise in the information provided on the particular plant which can be found in the native plant database, 2-3 months generally works fine. Toward the end of prescribed time period, look for emerging white root tips if any are detected, sow the whole batch of seeds immediately.
HOT WATER (mimics passage through a stomach or heat from a fire): Boil 3-6 cups of water for every cup of seeds. Don't use an aluminum pan or softened water, as either might introduce chemicals toxic to seeds.11 Turn off the heat when it reaches boiling, and let the water cool for a minute or two. Pour the seeds into the water and let them sit at room temperature for 24 hours. Seeds may still need to overwinter or be cold-stratified before they will sprout. Try this technique with Arctostaphylos columbiana, Arctostaphylos uva-ursi, or Ceanothus velutinus.
SCARIFICATION (mimics passage through a stomach): Line the inside of a lidded jar with a strip of sandpaper so the rough side faces inward. Put the seeds in the jar so they are surrounded by the sandpaper, close the lid, and swirl the seeds around until their seed coats are worn down enough to take in water. Unfortunately, it is difficult to tell how much scarring is enough and it varies from species to species, so we have no guidelines to offer. However, you might want to try this method with species that produce a berry or a pulp-covered seed.
5. Planting Seeds
Planting seeds in flats, pots, or seed beds, and carefully tending them until they are ready to be transplanted will improve their survival rate. However, it also requires a certain amount of time, effort, and space. Furthermore, seedlings growing in flats need to be replanted into pots once they have their second set of leaves before they develop too much root growth.
Planting seeds directly onto the final planting site requires less time and effort, and produces satisfactory results in most cases if a few guidelines are followed:
- Rake the area free of large clods of earth and rocks, and compress the soil slightly. Press the seed into the soil to a depth equal to its diameter, and cover it, preferably with sifted soil or sand; don't bury the seed too deeply. Small seed can be raked into the soil surface.
- Cover the soil with a thin layer of mulch, such as leaves, straw, or composted sawdust. This will soften the impact of raindrops and prevent the seeds from being splashed or washed away.
- Don't plant the seeds too close together! Try to space them so the plants will not compete with each other for sunlight and water. Be aware that some seed may be eaten by birds or rodents; you may find that certain species, such as beaked hazelnut, must be raised under some sort of protection and planted out as seedlings to prevent this.
- Keep the seed well-watered. If the planted area will receive occasional visitors and is near a convenient water source, consider marking your plot and posting a sign asking visitors to water it.
Native Plant Front Page
Plant Identification Data Base
Introduction | Selecting the Right Plant For the Right Place | Getting Plants
Aquatic Plants | Non-Native Problem Plants | Glossary | Resources | Credits