Wednesday, June 15, 2011

Sweet Clover

Yellow Sweet Clover, an invasive non-native plant species, has a special place in the history of my management efforts at Blue Jay Barrens. When I first bought the property, I didn’t know anything about Barrens ecology or remnant prairie communities or Southern Ohio plant rarities. In my initial quest for management advice, I was told by two different government agencies dealing in land management that I should broadcast Yellow Sweet Clover seed in all of the bare areas. I now know that this was sound advice if the goal was to control erosion and provide some herbaceous cover, but it was a terrible thing to do if you’re managing for native plant communities.

Yellow Sweet Clover will grow in poor ground and its ability to form a dense canopy allows it to shade out other plants. This makes it tough competition for many native plants. I shiver when I think of the millions of Sweet Clover seeds I spread across the barrens. Fortunately, things didn’t end in total disaster. Since I’m not a very trusting person, I only spread clover seed on a few of the barrens. Right or wrong, I wanted to see the results for myself before fully embracing the activity. Luckily for me, the result was an almost complete failure that I was later able to consider a success. Seedlings developed, but they all died. I’m glad it worked out that way even though I’m not sure why they died.

Things are fairly open beneath the clover canopy. Conditions are ideal for the growth of Sweet Clover seedlings. This is a biennial plant, so this year’s seedlings are next year’s flowering plants. After producing seed, the plant dies.

The flower spikes will produce an abundance of seed. The seeds can survive in the soil for up to ten years before germinating. This means that you have to eliminate the clover plants each year for a decade before you can begin thinking that you might have cleaned up the site.

The positive aspect of this plant is its ability to produce an abundance of nectar which attracts a wide array of bees, butterflies, moths, beetles and flies. Replacing a stand of Sweet Clover with a mix of native species will reduce the nectar supply, but will ultimately be a benefit to native animal populations. For instance, most moths and butterflies benefit more by having host plants on which to deposit their eggs than they do by having a food source.

After my failed attempt to make Blue Jay Barrens a Sweet Clover Heaven, I noticed that there were a few areas of clover infestation scattered across the property. It made me feel good that the incidence of Sweet Clover was about the same in the areas I had seeded as it was in the areas I had avoided. Control of Sweet Clover is not a high priority right now, but I try to clean up isolated infestations when I can. Pulling during peak flowering time seems to be the most effective control method.

At this stage the seed development isn’t far enough along for the pulled plant to produce any viable seed as it dries. I try to put the pulled plants somewhere that they won’t smother any natives. There have been times when I’ve carried the plants all the way back to the house and put them on my compost heap. This time I just laid them on an old cedar skeleton. I can’t see a Sweet Clover plant without thinking my early management blunder. I like to think that I’ve done enough positive management since to make up for those early years.


  1. Excellent post Steve, forgot to ask you if you are in the "different or same" species camp on the Melilotus alba? My neophyte opinion is different species, as the alba blooms later and has a few other differences.From what ive seen color vars of same species tend to bloom together.

  2. I agree with the two species concept. There are too many distinct differences to consider the yellow and white to be of the same species. I have the white here, but I only talked about the yellow because that's what I seeded.