Wednesday, September 28, 2011

Problem Weed in Pot

I had this idea that I could get ahead of the weed infestation in my winter annual pot by spraying when the weeds first appeared in the fall. This pot remained consistently plant free until about a week ago. That’s when I noticed a flush of green as things began to germinate. I decided to wait a few days to allow the plants to become more identifiable before spraying with herbicide.

The primary undesirable plant was chickweed, which is easily eliminated by a weak solution of glyphosate. A closer examination revealed a problem with my well thought out plans. I could see plants in the mix that were definitely not weeds. Spraying was removed from my list of weed control options.

This is Draba cuneifolia, a small winter annual that will grow through the winter and flower sometime early next April. At least I’m assuming it to be Draba cuneifolia. It’s hard to identify the Drabas when they’re this young. The only other option is Draba reptans, but that species usually germinates a little later in the fall and doesn’t reach this size until late winter. Either way, this is one of the uncommon Draba species that I’m trying to cultivate in this pot.

I persuaded President Lincoln to enter the frame for a size comparison to illustrate the tiny size of these seedlings. I took the time to weed this small space using a pair of tweezers, so things were clear enough to see the Drabas. At this stage, these are very fragile plants that are easily damaged, so it’s a rather delicate operation to remove weeds without compromising the integrity of the Draba root system. During the next few months they’ll have to withstand heavy rains, deep snow and freezing temperatures. It’s amazing that any survive the ordeal.

There are still a lot of weeds left to destroy in this pot. I may have to modify some tiny tools to make the weeding process a bit easier. I wonder if this is what’s meant by micromanagement.

Leavenworthia uniflora, another uncommon native winter annual, is also actively growing in the pot. Leavenworthia are a little more robust that the Drabas, but they’re still awfully small. Soil in this pot mimics as closely as possible the conditions found on the barren sites where these plants normally grow. That means there should be some Draba and Leavenworthia germinating out in the barrens. I’ve been looking, but I’ve yet to find any. The problem is that, even though I try to harvest as much of this seed as possible, the concentration of plants and the amount of seed falling to the soil within the pots is probably hundreds of times greater than what is found in any of the natural barren openings. You would need to search thousands of square feet of barren areas to find the same number of plants growing in this one pot. What I’m trying to convey is the difficulty of finding plants this small out in a natural field.

I guess I’ll just have to take part of a nice sunny day and tweeze the weeds out of this pot. I’m trying to produce enough seed so that next year I can plant a Draba/Leavenworthia bed. I should probably get the soil for that bed in place right away so I can get an early start on weed control. Tweezing weeds out of an 18 inch diameter pot is bad enough. I certainly don’t want to do the same thing to 30 or 40 square feet of bed.


  1. Very cool that you are cultivating these species! Last April we went out on a foray hunting these small creatures with our cameras!

  2. I second go native's comment about growing these. Is this for seed production to enhance or develop new wild populations?
    We have these species in Missouri dolomite glades (=barrens), too. What amazes me is that they can occur in such tiny and widely dispersed bits of appropriate habitat, over such a broad range. One wonders how in the world they got everywhere they occur?!

  3. Hi, Go Native. I hope you were able to get some good pictures. I have trouble taking photos of Drabas that have all of the plant parts in focus.

    Hi, James. I started growing these species in pots just to get an idea of how they developed. I was surprised when I first saw seedlings in September. Draba seed seems small enough to become airborne on a windy day and the winged Leavenworthia seed ought to be easily moved by the wind. The fact that so many apparently suitable sites are without these plants suggests that seed movement is not a common or a speedy process.