Should I grow common milkweed (aspecias syriaca) in Savannah, Georgia, US?

[nonbinary-naturalist]

explanation:

I moved from Pennsylvania to Georgia in March 2021. Before moving, there were three common milkweed plants in my yard, and I collected–very literally–thousands of seeds. I didn’t really plan on moving across the entire country, and I planned to plant and give the seeds away for free.

But now I’m in Savannah, Georgia, and I can’t figure out if I should be growing it down here too, I keep getting conflicting answers every time I try to find out. So I figured I’d ask on here, and hopefully someone who knows more about it can explain.

It would be really nice if it were okay to grow it down here, since, again I have literally thousands of seeds, and so far all we’ve been able to do is try to find people up north who want to grow it so we can mail some to them.

I have butterfly (asclepias tuberosa) and swamp milkweed (asclepias incarnata) plants I brought with me in containers, but I have yet to collect any seeds from the butterfly milkweed, and only got a few (very, very large, oddly enough) seeds from my swamp milkweed. And so far I haven’t had any luck finding any wild milkweed plants…

So the question is: should I grow common milkweed as far south as Savanna, Georgia?

I want more milkweed plants that I can give to people to help monarchs and other insects that rely on milkweed (I especially liked common milkweed in Pennsylvania because it always attracted large milkweed bugs, which I thought were adorable), but if it doesn’t naturally grow down here, I don’t want it to escape and cause problems with the ecosystem. I haven’t seen any in the area on iNaturalist, but that doesn’t mean it’s not here, it just means no one on iNaturalist has found them…(there were no small-flower pawpaw observations in Savannah until I learned how to identify them and found a bunch, so no observations definitely does not mean the species isn’t there)

EDIT:

I’m not worried about whether or not my seeds in particular would do well, I’m worried about what kind of impact the species itself would have on the ecosystem, since I can’t figure out if it naturally grows this far south.

[ID: A cropped image of a map of the United States, showing the state of Georgia outlined in yellow, with a red X and arrow marking the location of the city of Savannah, on the far east coast, more than halfway down the state. End ID.]

[cthawley]

I would advocate for not using seeds from PA in GA even if the species is found there. Many species are locally adapted, meaning that even though populations in different parts of the country are the same species, they still contain different genes (or frequencies of genes in the population) that adapt them to do well in their local climate. This type of local adaptation is quite common in plants (though I don’t know about milkweeds in particular).

Moving individuals from one population to another can mean that they are maladapted for local conditions in the new location, especially if the habitat is quite different in their “birthplace.” The habitat in PA will be fairly different from in Savannah. Worse, if individuals from transplanted seeds outcross with the local population, it can actually make this population have lower fitness. Over time, those less useful genes should be bred out of the population they were introduced to (in theory), but this can still have an impact.

For a plant like milkweed for which seeds/plants are sold, it’s possible that similar effects have already taken place, but I would argue that isn’t a reason to continue those negative impacts. I would suggest looking for local plants (that will almost certainly be adapted to conditions in the Savannah area), harvesting seeds from them, and planting those in Savannah. That way you can be sure of having plants that are well-adapted to the area, they will likely do better for you, and do a better job for pollinators or other insects that will make use of them in Savannah.

[aphili8]

It is a conflict… I’ve experienced the same thing. We’ve purchased native plants from plant sales, and goodness knows where the genetics originates from. Lately we have found a local nursery run by a botanist who specializes in local genotypes of plants… but we sure aren’t going to tear everything out and start over again. But we are definitely making the switch. I am guessing that at least some of your seed will be fit to survive in Georgia and it may be very tempting to grow it (and in the grand scheme of things probably not so bad, in a world where we are cultivating invasives). But I still think it’s a little tragic if we narrow the gene pool of a species to that of our particular plant in our yard, or that of some very popular online nurseries. I think the local diversity, even if we can’t tell the difference ourselves, is worth preserving, and could have a farther reaching impact than we know, as cthawley already mentioned.
Maybe it’s an opportunity to experiment with some new varieties? Looks like there are some very beautiful species that are more common in Georgia than the common milkweed. There are a good amount of redring and clasping millkweed observations there… or Sandhill milkweed in the south. I know it will be tough to find populations of them but looking at the species list for Georgia it should be easier than common, and could be fun. And they should support the large milkweed bug too.

[annkatrinrose]

Growing seeds adapted to PA climate in GA may not work very well. However, you can maybe still donate all those seeds you have! I found this page to be useful to determine which milkseeds to grow where and what seeds are needed for distribution:
https://monarchwatch.org/bring-back-the-monarchs/milkweed/milkweed-regions-seed-needs/

[Thunderhead]

I believe the best place to ask is the County Extension, there’s one in Garden City. I think it’s connected with University of Georgia.

[er1kksen]

This resource on monarchs and milkweed specifically asks people NOT to plant A. syriaca in Georgia: http://botgarden.uga.edu/wp-content/uploads/2018/03/milkweedinformation.pdf

It is considered nonnative in georgia.

[raymie]

The BONAP map says it’s native:

(Addded note: The light blue means non-native, so according to this map the only states where it is non-native and established are Montana, Utah, Oregon, Louisiana, and Texas, at least according to this map)

[nonbinary-naturalist]

Oh, good idea! I found the website, I’ll link it here for anyone else in Savannah who needs it.

https://extension.uga.edu/county-offices/chatham.html

[nonbinary-naturalist]

No, it’s definitely native to Georgia in general, but I don’t know if it’s native as far south as I am.

I went to Fort McAllister State Park yesterday and they have pamphlets about different butterfly species, which included information about Monarchs and milkweed. The pamphlet actively cautions against planting tropical milkweed, so I know they’re taking that seriously, but then they also suggest planting common milkweed alongside other Georgia-native milkweeds like tuberosa, incarnata, exaltata,, and verticillata.

It’s definitely native to the state of Georgia, what I need to know is whether it naturally grows as far south and as much on the coast as Savannah.

[Thunderhead]

I believe every US county has an extension office. The local one where I am is incredibly accessible, they offer a lot of help and several programs. I like to be able to talk to them face to face, too.

[ken_ohio]

I would suggest contacting two organizations with this question:

1. The Georgia Department of Natural Resources most likely has a native plant species division:
   https://gadnr.org/

2. I found this organization just by doing some searches:
   https://botgarden.uga.edu/conservation-science/georgia-native-plant-initiative/

You could also search the websites of universities in your area to see if any have current research programs for native plants.

And, you can see if your area has county parks. Those entities can also have native plant specialists.

[jasonhernandez74]

@raymie

The BONAP map says it’s native:

What the bonap map shows is that if any county in the state is light green (species is native in that county), then the whole state will be dark green (species is native somewhere in that state). You can see that Georgia has a few counties in yellow, which make the whole state dark green; the species’ rare presence in those counties means that it is present in the state.

What doesn’t make sense is why states with no light green counties, but with light blue counties, appear in dark green.

[aphili8]

I also find that the BONAP maps are not without error either. Well, I mean, that’s a no-brainer, nothing is. But there was a particular time in my life when I made the argument Salvia Azurea was native to New York based on BONAP maps, but a little more research found that it in the rare instances it was found in New York, it had very likely been brought there and was not native to the region at all. So now when I see a few scattered instances of a plant in a region on BONAP or USDA, I think that more research is needed before just taking BONAP at face value. Not that it isn’t a good source… just some things are not that simple.

Likewise, when a county is marked as not having had a species, particularly when its surrounded by other positive counties, I feel that there is potential for that species there, it just hasn’t been recorded yet.

[raymie]

I’ve found plants growing in counties that BONAP says they aren’t found in more times than I can count.

[RL7836]

I agree with the apparent majority to not grow Asclepias syriaca around your new location. In addition to the reasons noted, it’s somewhat of a ‘thug’ (IMHO). It spreads eagerly via underground rhizome and has very thick leaves. I’ve found that Monarchs prefer species that have thinner leaves (like A. incarnata) if given a choice (in my flower beds, I can no longer grow A. incarnata - the Monarch caterpillars eat 100% of the leaves each year). There are many Asclepias species. I suspect that a number of them would be a better choice than A. syriaca.

[er1kksen]

I saw that too, but varying sources are contradictory on the subject. BONAP is a great resource, but all that really shows is that USDA classified it as native and rare in Georgia in 2012 and herbarium vouchers from the yellow counties were entered in the database BONAP drew from at the time. A number of plants that have been reclassified as non-native adventives in NY over the last decade following closer studies of the literature and herbarium specimens still show as native on BONAP, as well as a few cases of the inverse situation. Some cases of ambiguous nativity are still unresolved and different authorities can be found to go one way or the other in contemporary publications.

Because the pamphlet I linked is from one of Georgia’s major herbaria with a research staff, and partnered with the Georgia Plant Conservation Alliance, Georgia DNR, and others I’d assume that the statement that Asclepias syriaca is not native to Georgia is the current consensus of researchers who’ve reviewed the subject more recently, and found that north Georgia populations previously classified as native were actually historical introductions.

This is similarly indicated on Georgia DNR’s page for Asclepias purparescens, which mentions A. syriaca as “a non-native milkweed that has escaped from cultivation in a few northeast Georgia counties.” https://georgiabiodiversity.org/natels/profile?es_id=17751

Weakley’s Flora of the Southern US, about as recent and authoritative as you can get, designates it as introduced to Georgia and notes that it’s expanding its range southward in general. On Facebook, the Georgia Native Plant Society put up a post last year noting A. syriaca as one of the non-native milkweeds not to plant, drawing some questions, to which they clarified that it had previously been of uncertain native status but more recently revised to being considered introduced.