Wednesday, March 10, 2010

Your Milkweed Shopping List

Maybe its the "weed" in milkweed that scares people. You'll see by the photos that many members of the Asclepias family are beautiful in their own right, often with stunning flowers. Monarch butterflies and their cousins, the queen butterflies, use milkweed as their host plant. By host plant we mean that they will only lay eggs on a milkweed so their larvae can feed on them to eventually become a butterfly. With the local plant sales starting this week, here are a few to add to your landscape. By planting several in your yard you are helping to preserve the monarch butterfly's migration, but you may also be delighted by other butterflies who also enjoy the flower's nectar.

Desert or Reed Milkweed  Asclepias subulata
A delightful lady once stopped me while I was buying a Desert Milkweed at Boyce Thompson Arboretum's Fall plant sale. She was an artist and admired the unique and graceful shape of this plant as well as its muted color. As we talked, I learned to appreciate this desert-dweller in a new way. She also told me about a shopping center in East Mesa with rows and rows of A. subulata. Of course I stopped there on my way home and was delighted to see male monarch butterflies patrolling  and cruising the milkweed! I also saw many monarch caterpillars chewing on the flowers and stems.

Desert milkweed is a low-water plant that thrives in full sun. When first planted, water deeply twice a week. Once it settles in you can water deeply only once a week during the summer and little to none during our winters. How much better can it get in our Phoenix heat? The Spring plant sale lists at the Desert Botanical Garden and Boyce Thompson Arboretum show that the Desert Milkweed will be available at both locations usually in one and five gallon containers. This is a fast grower, so buy several one gallon plants and let them find their home in that sunny spot of your yard that is often a challenge to showcase. Then keep your eyes open and see who visits!

Tropical Milkweed or Bloodflower   Asclepias curassavica
While not native to Arizona, A. curassavica grows well in our desert climate. It is frost-tender and becomes an annual during those cold winters. But in our recent mild years it is a perennial that thrives on a fall pruning to help it become fuller with abundant blooms in the Spring. When you do cut back a branch or two because it is getting a bit leggy, stick it in a pot of fresh potting soil and it will easy root creating a new plant. Bloodflower also grows easily from seed.

This milkweed seems to be a favorite of monarch butterflies around the United States and it is often hoarded by monarch enthusiasts eager to draw monarchs to their yard. We are lucky that it often grows in the Phoenix area year round. Tropical milkweed is usually found with the popular orange and red flowers, but all-yellow varieties are also available. While this milkweed takes full summer sun, it grows best with some afternoon shade. It needs more water than the Desert Milkweed, so water deeply twice a week during summer's peak. Last year during a high heat dry spell I covered my Tropical Milkweed lightly with shade screen for a few weeks to helped protect it from those scorching days when we all cry for relief.

Asclepias currasavica is on the plant list for the Spring sales at both the Desert Botanical Garden and Boyce Thompson.

 Narrowleaf or Arizona Milkweed
Asclepias angustifolia

Have a shady spot but still want flowers? Narrowleaf Milkweed is just for you! One of the rare milkweeds that favors shade rather than sun, A. angustifolia draws monarch and queen butterflies as a place to lay their eggs. In the Fall, a monarch butterfly deposited her eggs on Narrowleaf Milkweed at the Desert Botanical Garden Herb Garden. Two caterpillars each formed their chrysalis on a nearby Agave. The weather then cooled, so their transformation took longer, but by Christmas two beautiful male monarch butterflies emerged and nectared on nearby Fernleaf Lavendar to the delight of visitors.

Narrowleaf Milkweed will require more water than the Desert Milkweed, so twice a week deep watering in the summer will help this shade-lover flourish. Fortunately, since it is protected by shade, the evaporation rate isn't as high as other plants.

Unfortunately A. angustifolia isn't on the Spring plant sale list of either the Desert Botanical Garden (where it was in the Fall) or Boyce Thompson. But do ask at local nurseries if they will order it for you. Its a great find!

Pine-needle Milkweed   Asclepias linaria
  Pine-needle Milkweed also grows well in our desert and flourishes in full sun with little water. Once established, a weekly deep watering suffices.

Let us know if you find monarch caterpillars on A. linaria. The Southwest Monarch Study finds that they are a common monarch host plant at East and Southeastern Arizona locations, like Boyce Thompson Arboretum. But in the Phoenix area monarch butterflies seem to prefer other milkweeds. We don't know why that is or if it is true at all, so more data is needed. Pine-needle Milkweed will be available at the Boyce Thompson Arboretum Spring plant sale.

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