Removing Invasive Blue Porterweed

 

Blue porterweed is an eye-catching plant. With blue flower spikes extending for several inches and its patterned leaves, it makes a great addition to any native garden, especially if you want to support pollinators (it's a host plant for the tropical buckeye and the primary food source for at least five others). And it's edible (the flowers taste like mushrooms, which is weird, but cool). 

I set out to buy a couple for the backyard. 

This was before I realized how hard it was to find native plants or how scarce native nurseries are. It's also before I realized there was more than one ecotype of porterweed in Florida, or that one of them was invasive.

We went to the local flea market one weekend, which has an absolutely massive selection of plants. It's a collection of crisscrossing buildings and each end has its plant sellers. You can buy just about whatever you want, from fruit trees to herbs and veggies and flowers.

One of the sellers had several blue porterweeds on offer, so I happily took a couple. The pic at the top is one of them. I got them home, got them in the ground, and diligently watered them until they were established.

And then I read about the difference between Stachytarpheta jamaicensis (our native blue porter weed) and Stachytarpheta cayennensis (the import from Asia, which is now a Class II invasive species). Worried that I might have the invasive, I did as much reading as I could and poured over the plants to see if I could identify the telltale signs of S. cayennensis. 

The thing is, it's tough to spot those differences, even with native and invasive side by side. Eventually, I realized that I DID have the invasive, and they would need to come out. Not happy-making, for sure.

I managed to score a couple of natives from Bee Native (huge props to this brand new native nursery in Ocala!), removed the invasives, and planted the new ones. 

Given the difficulty in telling these things apart and the fact that invasive blue porterweed is sold all over the place, I thought I would post a few of the identifiers in case someone needed some pointers.

In the pic above, the top leaf is from the invasive type and the bottom is the native. There are some very (VERY) subtle differences. The native is a little more rounded. The quilting on the leaf is also slightly less pronounced. Finally, the serrations on the margins (leaf edge) point generally more toward the tip, while the invasive points more away from the leaf.

You've probably noticed something by now: All of these things are pretty damn subjective. So, here's something else to help.

In the pic above, you'll see the flower stems. The invasive is green all the way down. The native porterweed is purple. That's easier to spot.

Finally, there's this pic. This is the stem of the invasive and you can see that it's woody. Most of the stems are woody, which is one reason for its upright growth habit. The native porterweed is more herbaceous and has a low-growing, sprawling growth habit.

Anyway, hopefully, those tips will help you tell if something you're about to buy (or have already planted) isn't the native variety. If you want more info, check out the Florida Native Plant Society's entry on it (and join your local chapter, it's fun!). This video from Fruit of Labor is also VERY helpful and covers most of the things I've listed above, so check it out.