Probably the most common method is to prepare a mix of new perlite and vermiculite and thoroughly dampen it, pack it into new or washed pots, sow the seed on top, cover lightly and place the pots outside in the winter. Almost every grower has his or her own method of accomplishing this. Southern species and many large flowering hybrids require no stratification. This is especially true for northern species. Cold stratification consists of growing the seed in a moist medium at temperatures just above freezing. Many penstemon seeds require a long cool, moist stratification time before they will germinate. Germination of Penstemon strictus was good for seed up to 6 years old. For example, the following table shows the results of a study comparing the germination of penstemon seed from one to ten years old. You will usually get reasonable germination for about five years after collection, and possibly even longer for some species. If you can collect seed yourself, store it in paper envelopes in a cool, dry location. Penstemon seeds often germinate best after being stored dry for 6 months to a year, so do not discard seed that is not fresh. You may also find out that in one year a technique works very well and the next year, it does not. These techniques will also vary with the quality of the seed. Conditions may include but are not limited to stratification, scarification, alternating temperatures, chemical treatments, light versus dark, and seed aging. The American Penstemon Society’s Book on penstemon (Growing Penstemons: Species, Cultivars and Hybrids) can be used as a starting point in determining seed germination conditions. Very seldom will you get 100% germination of seed. It is a good idea to sow a quantity of seed that is several times the number of plants you desire. Through the American Penstemon Society and many commercial seed collectors, you can obtain seeds and grow species and varieties for a wide variety of locations and growing conditions. Make sure federal and state regulations are followed when collecting seed from the wild. Seed may be collected in the wild or from a garden. The first step in propagating seed is to acquire the seed. Not everyone has a greenhouse in which to start plants. The method to use is often dictated by the facilities available. However, for most of the penstemon species, some type of seed treatment is beneficial to enhance germination and reduce seed dormancy. This is especially true of species from mild climates. For example, some penstemon species and varieties require no pre-germination seed treatment. Propagating penstemons from seed requires some knowledge about the general background of the seed and also about germination procedures.
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