Saturday, July 18, 2009

Nonnative Species V. Invasive Species

There are many garden species, common day lilies for instance, that: oblige the grower, spread but can be removed, and do not cause problems for adjacent wild areas.

Then there are the really invasive plants that will find disturbed areas and take over to become a destructive monoculture. Buckthorn and garlic mustard are not very good for the local wildlife species to eat, but will spread, especially to disturbed areas. I garden a small area of land near an urban center, formerly grass. Buckthorn and garlic mustard consider my disturbed area a playground. Garlic mustard is very clever, it finds it’s way to every open space here.

A funny thing happens when you pull out garlic mustard on a recently invaded creek bank. Other species that have been growing there, have been crowded out by the garlic mustard are still growing in between. Garlic mustard is a pest, it is a self serving, spreading invasive with the ability to create a monoculture of itself.

Local chefs have developed recipes for garlic mustard. Planting it is not good, but in areas where it is taking over, garlic mustard lasagna is reputed to be served in spring.

Here in Michigan there is interest in looking after our remaining wild areas, and in reclaiming degraded areas. Garlic mustard pulling is a common spring pastime.

Another notable invasive species here is buckthorn. Introduced as an ornamental, buckthorn is a small tree or large shrub, it will take over an area and when it does, nothing will grow in the understory. It out competes everything. We stopped mowing the lawn near our creek and buckthorn created a buckthorn monoculture in 10 years. There was nothing growing there but buckthorn. (I have since removed it, and must remain ever vigilant, removing young plants) Some stewards will resort to chemical control, making a special wand and cutting the trunk about a yard above the ground, smearing the stump with glycosol and walking away. I personally do not use chemical solutions. I use the method of mechanical sawing and remove growth from the stump at least twice a year, the buckthorn stump will not survive consistent leaf removal.

I have seen large piles of sawn buckthorn bodies in parks, and I have seen more reserved approaches to buckthorn removal. Buckthorn has a male and female plant, the destructive berries that will plant themselves and spread all over appear only on the female plants. Female plant removal is a priority.

Phragmities is also a problem around lakes and in ditches along freeways were there is runoff. There is a native phragmites, but it is small.


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