Latin Name: Apocynum cannabinum
Common Name(s): Dogbane
Family: Apocynaceae
Size: Around 3 feet tall. Can establish large colonies by spreading rhizomes.
Life Cycle: Perennial
Distribution: Most of North America along ditches and streams and in moist meadows.
Light Requirements: Full sun to part shade
USDA Zone: 3a to 9b
Drought Tolerance: Medium
Fire Risk: Presumably low while it is growing, given the soft watery leaves and need for moisture. If growing near a structure in a fire-prone area it is probably best to cut it down after it dies back and dries to avoid the seed fluff and dried plant matter fueling any fires.
Cultivation Notes
Dogbanes are tough and adapt well to the garden. A. cannabinum can adapt to a variety of soil conditions but prefers a moister spot in sun or part shade with sandy soil. They can take some drought once established but survival is much better on the west coast with regular summer moisture, hence their preferred habitat in the PNW of river and stream banks. They can take being waterlogged in the winter, unlike most in this family. Fertilization is not needed, as the plants do fine even in poor and gravelly soil. Slug control may be needed when the plants are young, as heavy feeding by non-native slugs can kill young plants. Simply remove slugs in the evening and kill in soapy water.
Ecology
The charming flowers bloom from July through August and are very attractive to pollinators. The seeds are consumed by birds in the winter, when few food sources are available. The plants are hosts for a wide variety of lepidopteran larvae and, when the flowers are taken into account, absolutely irresistible to butterflies and moths.
Uses
Dogbane is toxic, containing cardiac glycosides and causing heart issues and skin blistering. It has been used for a strong and high-quality fiber, hence the species name cannabinum, and the latex can be turned into rubber. The seeds are reportedly edible and the latex has reportedly been mixed with clay and hardened into a sort of chewing gum, but due to the toxicity of the plant I really do not recommend consuming it in any way. It seems likely to me that the clay was both a filler and a neutralizing agent for the toxin. Again, however, do not eat this plant. Mediocre organic chewing gum is not worth a heart attack. If you are going to experiment this the dogbane family, experiment with Asclepias syriaca or A. speciosa. A lot less dangerous.
Propagation
Seed or by division. Seeds are easily collected and can be sown directly in the fall or in spring. Sow just under the soil surface. Germination can be slow and often is irregular. If planting in the late spring, cold stratification will likely be needed for up to two months before germination will take place. I have not had too much luck with seeds, though. I have successfully propagated the plants by letting seedlings develop naturally, then moving them. I have also taken divisions with some success. They do not seem to resent disturbance as much as milkweeds, their close relatives.