October 1, 2016
With drought and water conservation many gardeners are turning to native shrubs and plants for landscaping because they are naturally suited to our wet winter-dry summer environment. With many native plants in close proximity, why not just collect some seeds from existing plants and propagate them for your garden?
Here are some factors to take into consideration when thinking about propagating native plants from seed.
Propagation in the wild starts with seed dispersal. Mother Nature uses mechanisms such as wind, water, animals, birds, gravity and ballistic energy to disperse seeds from the mother plant. Next, the hard coating on the outside of the seed has to break down so the embryo can activate. This might happen in a bird’s gut during digestion, in a stream as water softens the seed covering, or directly in the soil wherever the seed is carried by the wind. Some seeds go into a state of dormancy until the warmth and moisture is right for germination. Once the seed is in supportive soil and the right weather conditions, the embryo begins to develop and sprout.
Let’s look at how this might translate to home propagation by seed. First the gardener needs to collect the seeds. Researching the plant’s mechanism of dispersal is key. For example, lupine and poppy plants discharge their seeds via a ballistic mechanism as they explode from their pods. So they must be collected before they are ripe. Some seeds need to be collected when they are dry while others like toyon are embedded in the fruit of the plant that is then crushed to pulp to extract the seeds.
Some seeds need to experience the cold conditions of winter before germinatin, called stratification. Seeds can be stored in a refrigerator for one to three months while they are watched for signs of germination.
For many seeds, the hard outer coating of the seed needs to be broken down either by mechanical means or chemicals. This process is called scarification, which includes hot water, dry heat, fire, acids, or mechanical ways like rubbing the seeds on sandpaper. Once this is done, usually the seeds are stored for some time to wait for spring conditions.
To store seeds, air-dry them to prevent mold or mildew. Place them in labeled envelopes in jars with name of the plant and the date collected. Mothballs or desiccants can be added to retard moisture and kill larvae. Short-lived seeds, such as acorns, maple and grass seeds, should be sown immediately while moderate- to long-lived seeds, such as California coffeeberry, should be stored in in a refrigerator with a desiccant for one to three months.
When it is time to plant, you need soil that has good aeration for your seeds, is disease- and pest-free, and holds moisture well. To reduce the chance of disease, use pasteurized media. Using sterilized large surface flats for propagation reduces the chance of pests and pathogens. Make sure your flat has good drainage and sow your seeds at a depth of 1½ times the diameter of the seed. Cover the top of the soil with vermiculate to keep the soil moist.
Once you have true leaves and a sturdy stalk on your plant you can transplant it to its own container. Some natives require a season or two in a container before you set it out in our garden. Natives need moisture when they are first planted in your yard and can be weaned to drier conditions over the next two years.
The key to native propagation from seed is researching the plant’s means of dispersal so you can collect the seeds and learning the requirements for germination. For propagation guidelines and requirements, reference the book “Seed Propagation of Native California Plants” by Dara E. Emery. Or go to the Marin Native Plant Society website at cnpsmarin.org.