Got Nature? Blog

Black locust
Credit: Richard Webb, Bugwood.org

I recently received an email from a private landowner:

I had a question for you about Black Locust and the Indiana’s Most Unwanted website. I saw Black Locust is listed on there even though this site says it’s native range includes Indiana. I see invasives.org mentions that it can become invasive in prairie and savanna areas. Can you shed a little light on this? I mean, I see it all over but not to the point of other invasives. Is it invasive in woodlands or just open areas? What is the deal?

Also on the Most Unwanted site, I see a lot of the plants say something like “Note – do not buy, sell or plant Asian bush honeysuckles,” but Black Locust does not. Any idea why? This site doesn’t really give a good feel for their classification as invasive, aggressive, noxious, etc. I didn’t know if there was a better site that could give me an idea for that or not as well.

I guess mainly I’m confused since it’s a native, it wouldn’t seem to me that it should be an invasive.

Thank you for your assistance.

This landowner has some really good questions regarding a tree species that is found across the state of Indiana. Now I have been talking on and off with this landowner about various species over the past year or so as he is fighting the good fight and trying to eliminate invasive and non-native species from his property but is also attempting to re-vegetate with native species. This is not the first time that I have had this discussion, so I thought why not answer his question so that others could also get to the information?

The websites this landowner provided are all great sites with tons of information for a bunch of different species. So inevitably when you get lots of great information about one species, it is easy to skip or unintentionally omit some details for other species. I hope the folks behind sites like these continue to build these great sources of information, update them with current best management practices and add new species as they become problematic.

Now, onto the questions.
Black locust, Robinia pseudoacacia, is native to the state of Indiana (Deam 1940, Flora of Indiana). However, when we talk about species that are native to the state, they may not be native to the whole state. With the settlement of the Midwest, it is thought that European settlers brought black locust with them as they traveled due to its fast growth, wood quality and even perhaps for its nitrogen-fixing capabilities. There are numerous species which may be native to one part of the state but not others. One example of this, bald cypress, Taxodium distichum, is native to southwestern portions of the state where bald cypress swamps can be found, but it wasn’t historically found in the dunes of northwestern Indiana. A map of its native range can be found here.

I commonly have the discussion of the “official definitions” of invasive, non-native, exotic, aggressive, noxious, weed, etc., with folks. These definitions are an area of much debate in scientific literature and among professionals that regularly work to manage these species. It is my belief that “invasive” species can be both exotic (not from the geographical region in question) and native (belonging to the geographical region in question), just like exotic species don’t have to be invasive (grow and spread aggressively). Noxious plants (“any plant, or plant product, that can directly or indirectly injure or cause damage to….”) can fit into each of those descriptions, and then of course, there is the definition of a weed…a plant that grows in an area that we don’t want it to. Everyone has their own opinion though, right?

There are many places to look up species-specific information on a state-to-state as well as a county-to-county level. For example, I like to use two websites: www.bonap.org and plants.usda.gov. Unfortunately, there are so many species and so many records that are needed to update these types of databases that they may not accurately represent what is truly out there. Plus there are the differences between historical records and current records which can bring about another debate.

So to wrap this thing up and provide short answers to Scott’s questions:

Q: Is black locust native to the state?
A: Yes.

Q: Can black locust be invasive in prairie and savanna habitats?
A: Absolutely! It spreads aggressively into these environments, especially in the absence of disturbance (another topic for another posting…).

Q: Is it invasive in woodlands or just open areas or what is the deal?
A: Mostly in open areas. It doesn’t tolerate high shade very well.

Q: Any idea why websites don’t suggest to “buy, sell or plant” even though they list it as an invasive (paraphrased)?
A: No, I don’t. That said, I am not familiar with where to buy seedlings, but then again, I don’t have an interest in planting them!

In closing, would I plant black locust? No, I wouldn’t unless I intended to use the trees as a crop. Black locust makes great firewood and great fence posts, and the flowers taste pretty good in the spring. However, they can grow and spread quite aggressively through root suckers as well as by seed. Commonly the little patch of a few trees turns into acres and acres!