Saturday, April 7, 2012

Put This Target In Your Sight (or Stomach)

Garlic mustard (Alliaria petiolata), native to Europe, is an invasive thug that has spread far and wide over a good portion of North America. Introduced to North America by early settlers for supposed medicinal qualities and for culinary purposes, this competitive biennial quickly invaded woodlands and displaces native wild flowers and tree seedling. The picture above shows garlic mustard in bloom. With the warm spring, I've seen garlic mustard already on the verge of blooming although in an "average" spring, we don't see it blooming until late April or early May. To the left is the first year portion of this biennial which is simply foliage. This foliage stays green throughout the winter and is easy to target in late March or early April for removal as it is very conspicuous. The second year is when the bloom stalks appear above the foliage on this 1-3' tall plant. Flowers left to "go to seed" will drop hundreds of seeds that can remain viable for up to seven years in the soil. This plant will muscle out all but the hardiest competition and I've seen the entire understory of woods carpeted with this opportunistic invader. Controlling/eradicating garlic mustard is thereby a daunting, frustrating, multi-year challenge targeting not only 1st and 2nd year plants but following generations that germinate each year. Seeds are typically spread by the fur of mammals, birds, flowing water and thru human movement (soles of our shoes). If manually removing garlic mustard, strive to get the entire root out as well (as you would a dandelion). See to the right for an idea on the mass of roots that this plant will establish. Herbicide use, while effective, can be challenging particularly if there are still desireable plants in the vicinity of the garlic mustard. A non-selective herbicide (i.e. Round Up) will kill all target and non-target plants so the timing is important. When I've sprayed garlic mustard at RBG, I've done it on warm days in March when little else has emerged and the herbicide has enough time (at these cooler temperatures) to wipe out the garlic mustard before it gets to the blooming stage.If garlic mustard is manually removed, it's recommended that the collected plants are put in black garbage bags and taken to the dump (not the compost pile). The concern with leaving "pulled" plants is that they may re-root or even try to bloom quickly and reproduce (drop seed). There has been some research in to the effectiveness of cutting off the flower stalks prior to bloom stage so the second year plants ultimately can't reproduce and die. The timing has been debated as you ideally don't want new flower stalks emerging to finish the flowering and seed set. When I worked at Fernwood Botanic Garden (Niles, MI) we had many patches of garlic mustard in the woodlands and just as the flower stalks started to lengthen above the foliage, we would go out with weed whippers (string trimmers) and cut them back. We had some success with this approach and only followed this methodology as we lacked the resources for hand pulling and were wary of herbicides in this diverse woodland setting. There are many websites dedicated to providing information on this problem plant and these will also include removal recommendations as well as details on preventing the further spread of this aggressive biennial.

All parts of this plant are edible. The young leaves and flowers, when chopped up, can be used to provide pungent garlic flavor to any dish. The summer leaves are more bitter but young leaves have the best taste. The roots of this plant are also edible and can be processed like horseradish. The best time to collect the roots is in early spring or late fall. I've seen all sorts of programs and read various recipes on the use of this plant for culinary reasons and while it's nice to see at least something "good" about this plant, it's not realistic that human consumption will dimish the foothold that garlic mustard has established. We should all be vigilant in locating this plant and now is the time for eradication efforts. If you have neighbors with garlic mustard, don't hesistate to bring up the four primary implications of allowing this plant to further spread. Garlic mustard displaces native woodland vegetation, degrades wildlife habitat, displaces rare plants and can cause long term degradation of forests by shading out tree and shrub seedlings (taken from WI Extension bulletin). Keep an eye out for garlic mustard and show no mercy.

No comments: