Planting milkweed for endangered California Monarch butterflies

 

2021 saw an uptick in the number of Monarch (Danaus plexippus)  butterflies at the Monarch Grove at Pismo State Beach in Central California, the largest sanctuary in the state. Counts in recent years revealed a 90% population drop from 25 years ago. In 2020, there were 300 butterflies. This year, the trend is more favourable with than 20,000 counted.This is a far cry from the past. In the 1980s, there were 4 to 10 million butterflies overwintering on the California coast, but those numbers dropped in the 1990s and a 1997 count revealed 1.2 million butterflies. From 1998 on, there were never more than a few hundred thousand monarchs. 

Major threats to monarch population are climate change causing extremely wet and cold conditions in the Oyamel forests of Mexico,  loss of milkweed habitat (due to uptick in use of pesticides like RoundUp, Permethrin for West Nile control etc), deforestation (including strangely the removal of the invasive Australian eucalyptus for fire safety reasons, which monarchs seems to favor) and diversion of water for human purposes in overwintering areas depriving monarchs of much needed water. 

The Xerces Society for Invertebrate Conservation encourages California residents to grow native milkweed that butterflies feed on. The milkweed is a vital host plant critical to the butterflies' existence, providing a place to lay eggs and food for their baby caterpillars, nectar for the butterfly, and chemical compounds that make the monarchs distasteful to predators. 

Narrow-leaf milkweed

Native to North America, milkweed (Asclepias syriaca) comes in a wide variety of species and colors. Make sure to choose a variety native to California. Two commercially available native California varieties are: showy milkweed (Asclepius species) and narrow-leaved milkweed (Asclepius fascicularis). Lesser common but just as suitable are the Woollypod milkweed (Asclepius eriocarpa) and heartleaf milkweed (Asclepius cordifolia). The non-native Tropical Milkweed may disrupt monarch migration patterns, because of it's longer growing season, so don't plant it unless you're willing to cut it back to 6" or less from Oct-Feb. More details here

You can also find more tips on planting milkweed here

Lifecycle of Monarch butterflies

Milkweed seeds in the wild drop to the ground in late fall and delay germination by overwintering and waiting for the soil to heat up in late spring or early summer. At home you can mimic this process of 'Cold stratification' by initially putting seeds in a sealed plastic packet in a refrigerator then planting in late spring in moist peat-rich soil between 18 and 24 inches apart and no deeper than the existing soil line. No need to add fertilizer though some compost is ok.  

Milkweed loves to bask in hot sunshine. These plants require from 6 to 8 hours of direct sun exposure every day. 

This drought-tolerant plant, once established it needs little to no water from you. It’s a weed that survives on morning dew. 

Milkweed is no exception to pests like aphids, whiteflies, and leaf miners. Don’t use chemicals to treat. Try bio-friendly options like a jet of water or ladybugs etc. 

Remove any diseased leaves suffering from black fungus or mildew. Throw in trash. Do not compost diseased items.

References:

1] “How to Germinate and Grow Milkweed Seed.” American Meadows, www.americanmeadows.com/blog/2015/06/11/how-to-germinate-and-grow-milkweed-seed. Accessed 5 Feb. 2022.
2] Graff, Amy. “2,000 Monarch Butterflies Were Counted in Norcal in 2020. This Year, There Are More than 100,000.” SFGate.Com, San Francisco Chronicle, 9 Nov. 2021, www.sfgate.com/bayarea/article/western-migratory-monarch-butterflies-California-16595196.php.