Asclepias - does it affect the soil?

[Jacqui_in_NZ]

Hi Everyone,

I am in New Zealand where the Monarch arrived (presumably blown on a storm) in the 1800s. It wasn't until the early 1900s that Asclepias were introduced. We have two relatively common species: A. physocarpa and A. fruticosa, and there are two other species meant to be available in NZ, but I haven't found a nursery stocking them as yet.

I would like to ask a question about the plant, especially for those who live in countries where it is a wildflower.

I have found that where I once found prolific stands of A. physocarpa and/or A. fruticosa (the only two species that grow easily in this country) after a few years the plants have almost completely died out in that place.

Through those plants growing, seeds will have been scattered along the road and over the hill etc, so it isn't a major problem, I can always find Milkweed, but I was wondering if the plant actually changes the composition of the soil, so that it has become too alkali or acid, and that's why after a few years the plants don't grow in that place... This happens with Pinus radiata - after two or three crops the soil is no good for pine.

Does anyone know of any research that has been conducted that proves or disproves my theory?

We are currently working on restoring an overwintering habitat, and I have been told that Swan Plant was prolific there in the 1960s, but there isn't much there now - and neither are there many butterflies overwintering in the trees there (it's midwinter here in NZ).

Hope someone can assist!

Jacqui

[Chip]

Jacqui: Many of us who have observed patches of milkweeds from year to year have seen large populations of milkweeds disappear for no apparent reason. However, since it is known that some species of milkweeds are subject to attack by root fungi, it is possible that fungi could be responsible for some of these crashes. Other possibilities include root feeding beetle larvae and nematodes. Soil modification by the plant would not be high on my list of potential factors. Chip

[Jacqui_in_NZ]

Thanks for that, Chip!

Jacqui

[Paul Cherubini]

Does anyone know of any research that has been conducted that proves or disproves my theory?

Jacqui, you might want to ask Dr. David James <david_james@wsu.edu>
David did his Ph.D. thesis on the biology of monarchs in southeast Australia and spent years studying and rearing them in the Sydney region (where A. fruticosa is common). David will also likely be attending the Monarch Conference in San Luis Obispo, Calif. on Dec. 8-9. If you come to this meeting I'm sure David would love to meet someone like you that is from the same region where he spent most of his life.

[Jacqui_in_NZ]

thanks for that Paul.
It would be great to get together with David - but I won't be at the event this year unfortunately.

I will get in touch with David, though, it would be good to chat with him.

Cheers

Jacqui

[Mona Miller]

I think the problem is that the Gomphocarpus are tropical plants (native to Africa) and if the winter is too harsh then they disappear (die). It is a good idea to make sure you have seeds for next year. Mulching a bit in the winter may help protect them.

The butterfly weed, Asclepias tuberosa is a perennial. I read in Urquhart's book that New Zealand is supposed to have that plant. It is a great nectar source. It is not greatly appreciated by Monarchs, but they will use it.

[Jacqui_in_NZ]

Yes, Mona, we do have Butterfly Weed - but it was hard to find. I think because it's been listed (although that listing has lifted) as a pest plant, people were not telling anyone they had it.

I have found eggs and larvae on mine, and gave a leaf to large larva to eat and he got stuck into it.

I'm looking forward to having this plant in future years.


Jacqui

[Mona Miller]

Yes, Mona, we do have Butterfly Weed - but it was hard to find. I think because it's been listed (although that listing has lifted) as a pest plant, people were not telling anyone they had it.
I have found eggs and larvae on mine, and gave a leaf to large larva to eat and he got stuck into it.
I'm looking forward to having this plant in future years.
Jacqui

If you deadhead (cut off the spent blooms) it will flower again. I do this with some of the stalks. The other stalks I leave to seed after they have finished flowering.

[Jacqui_in_NZ]

It's midsummer here, and the plants are only six inches high. Not a flower in sight yet. I wonder if I should fertilise the plants? Or what else could I do to encourage growth? Am excited about seeing it bloom.


Jacqui

[Mona Miller]

It's midsummer here, and the plants are only six inches high. Not a flower in sight yet. I wonder if I should fertilise the plants? Or what else could I do to encourage growth? Am excited about seeing it bloom. Jacqui

Denise Gibbs would tell you to pinch them back a bit it will encourage them to branch out and you will have more flowering.

http://www.perennials.com/seehowto.html?item=9
Scroll down to this section "Pinching for Height Control"