From seed: Seeds need light to germinate so just gently press them into the soil on their sides without burying them. Keep soil moist. Some seeds germinate in as little as 2 weeks after planting but others in the same bed continue to germinate for 1-2 months afterwards.
Narrow-Leaved Milkweed (Asclepias fascicularis) and Showy Milkweed (Asclepius species) are flowering perennial plants that are native to California and also found elsewhere in the western US below 7,000 feet.
According to Calscape, Milkweeds are probably the single most important host plant for Monarch butterflies in California. These plants are eaten by Monarch caterpillars but the leaves return and hopefully Milkweed gardeners will be rewarded by the presence of beautiful Monarch Butterflies. Narrow-leaf Milkweeds die back in winter and revive in the Spring. The best time to plant milkweed is in the Fall once rains have started. If planting from seed, incorporate them into the soil immediately after spreading them.
Milkweeds grow from 1.7 to 3.3 feet tall and 1 foot wide. They flower in Summer and Fall. Their flower color is white, lavender. Summer irrigation maximum should be 2 times per month once established. They tolerate a variety of soils, sandy, clay and saline. They like all types of drainage.
Narrow- Leaf Milkweed works well with a variety of other plants. Also, plant a number of Milkweeds in proximity so that caterpillars will have a sufficient amount to eat. Use with showy, nectar-rich plants that will attract adult Monarchs, such as Indian Mallow (Abutilon palmeri), Ceanothus sp., Western Thistle (Cersium occidentale), California Aster (Corethrogyne filaginifolia), California Fuchsia (Epilobium canum), Buckwheat (Eriogonum sp.), Mint (Monardella sp.), Monkeyflower (Mimulus sp.), Penstemon sp., Sages (Salvia sp.), Apricot Mallow (Sphaeralcea ambigua)
Things to consider when planting Milkweed. Plant in an area away from cats and dogs since milkweed is a moderate to severe poison for these pets.
This may be obviou,s but never use any pesticides on this plant or nearby because doing so will be fatal to Monarch caterpillars