Thanks, I wasn't previously aware of Ophryocystis elektroscirrha, but just read up on it on Wikipedia. By cutting down the plants, are you also decreasing the number of butterflies that emerge on the milkweeds? I'm not clear on the seasons involved with the butterflies' cycle.

It is recommended that tropical milkweed be cut back in November both to reduce the chances of OE developing and to encourage the monarchs to travel farther south.

Tropical milkweed in California

Igteacher, the map on the linked site show the southern migration of the monarchs in the eastern U.S. The western population migrates to the coastal areas of CA (Sonoma County to San Diego). CA Monarchs

Frank, I have never had a problem with attracting monarchs. Much more common is a worry for having too many for the supply of milkweed in my rather small yard. Observation has shown that most females tend to favor placing eggs on the tallest plants in the sunniest locations in my garden. When those have been stripped bare of leaves by the caterpillars, the cats wander to the surrounding milkweed plants, that have been growing around the mature plant(s), to feed. So cutting the bare stems of the oldest plants does not interfere with the process. Sometimes I have to move caterpillars from one patch of milkweed, to another location that has more food available.

I usually have to cut them to the ground in fall because a)they start looking scraggly and b) can't keep up with the aphids any more. They start reblooming early spring and never stop.

Thanks for all the comments. I wasn't previously aware of the OE issue. So, am I right in thinking that the main difference between the tropical and native varieties of milkweed is that the tropicals bloom longer in the winter, leading the way for conditions that worsen the OE problem? So we should explicitly be choosing milkweeds that do not bloom in winter (or, if we have them, cut them down)?

Frank, that's what is recommended by experts whose talks I've gone to - plant native milkweed or make sure to cut back the tropical variety each winter.

OE is pretty ugly. And you can tell from the pupa which has black streaks in it. If the cat comes out the wings are often folded and will never straighten. I read that if you see a marked pupa, put in the freezer, it kills the virus and the pupa.

Hi- I am in Texas and found your comments most interesting. I grow in my yard not the tropical milkweed but the other kind. Our HOT weather is winding down and the pods of the milkweed have started to split. I remove the seed pods and send the seeds all over the US. A person from San Pedro & also Corona asked me when they should plant these seeds? Oh and the monarchs have been the most astounding in my yard! I still have milkweed coming up and no flowers yet and have seen butterflies attracted as well.

I also am excited that I registered my Yard as a Wildlife Habitat with the Wildlife Association. I received a certificate and soon a yard sign to come.

I was born in Oceanside and grew up in Southern CA.

Hi, Gretchen. That is great that you have had success with the narrow-leaf milkweed. I would rather grow the local native species, but have not had success keeping them going long term thus far. The germination info online is mixed. This source (page 302) states that narrow-leafed seeds sprout after 15 weeks of stratification. To reduce the risk of rot, the seeds can be stratified in damp sand at 35-40°F, then planted out in very early spring.

I know about the Wildlife Habitat program, but never considered signing up. Right now I am looking out the office window at a rat eating the bird seed, and not thinking harmony with nature thoughts... Or maybe I am. My first were "Where is that Cooper's hawk?" and "Why doesn't she help eliminate those!" ;)

Is your habitat/sign location visible by passersby? It would be nice if more people became aware of how even a few small efforts can help wildlife. A few of the gardens here are geared towards wildlife, but most are just things they pay someone to maintain for them. They will rave about the birds and butterflies at my place, but they cannot be bothered to purchase even a single shrub to attract them to their own garden.

I read to control OE that tropicals should be pruned to the ground during the winter to control OE overwintering.

Gretchen that is so cool! You have inspired me to look into doing that as well!