Monday, December 10, 2007

Black Plastic

A few weeks ago I put up a post talking about aggressive and invasive plants and how to deal with them in the landscape. To take a look at that post you can simply click here. When one of these plants has taken hold in the landscape it can be very overwhelming. Inevitably it becomes much more work to remove it than one might think. Invasive plants can often propagate themselves from the smallest piece of leaf, stem, or root tissue left in the soil so you really have to make sure you excavate the plant entirely. As with some cases, like the situation I wrote about before, you may be revisiting and re-pulling the same plant species for years after discovering its negative affect in your landscape.

With that in mind, I did receive an email from a great HSNY supporter and friend who added a suggestion that I forgot to mention earlier. The original question was, after many years of trying to simply pull and remove these incredulous plants, is there anything else I can do?

Another option is to attempt to smother and suffocate the plant by laying down black plastic. When I used to live in Massachusetts, educating people about changing their front yards into natural meadows seeded with native wildflowers, I often began by explaining how one would start by laying down black plastic. Here in the city I have seen black plastic used in many situations where the homeowner or super was trying to regain a piece of land overrun with annoying and aggressive weeds.

This is what you do. You should be able to find black plastic at any major retailer or garden center. It comes in rolls of varying length and thickness. What you are looking for is a heavy duty plastic that is the same as what they make construction-grade garbage bags out of, roughly 2-3 millimeters thick. I suppose if the area was small enough you could simply cut and use a contractor’s garbage bag that has been made flat. Lay the plastic over the area to be reclaimed and anchor the plastic with heavy weights (bricks, cinderblocks) or by driving stakes through it to keep it in place. So the area does not look like a complete eye sore, I lay down mulch over the plastic so that at least I am looking at wood chips or some other kind of decorative mulch as opposed to the ugly black plastic. If the area is still a focal point I have even recommended placing planted containers on the plastic so that there is still a visual while you work to reclaim the area underneath. Eventually when you pull up the plastic you can incorporate the mulch into the soil so you have not wasted that part of your investment. By cutting off all light and fresh air to that area the seeds, stems, and roots of unwanted plants will die back with a less likely chance of return.

This sounds very easy to do, and in fact, it is. There is one catch, however. To ensure the success of this plan of attack, it is imperative that the plastic be laid down, undisturbed, for one complete year. No exceptions! Letting your impatience take over, by figuring that “six months must be long enough to do the job”, I assure you is not going to help you at all.

You see, a horticulturist will tell you that there are summer weeds and winter weeds. Some weeds set seed that germinates in the spring or summer while others can set seed in the fall that will not germinate until the following spring. Therefore you have to consider weed control in the dead of winter just as much as you do during the dog days of summer, and again, you must have the plastic laid down for a full year. Then you have invasive species in addition to the weeds. Since these plants can be so persistent and aggressive I think it is best to smother them for as long as you can stand it. The backyard of a business next to my home in Queens has had plastic laid down for almost a year now. They should continue to keep it down for a few more months and then it will be spring and an ideal time to re-landscape the area. After a year the plastic can be taken up and the area cultivated. I would take a shovel and single-dig the entire area, incorporate a 2-3” layer of compost on top of the area being reclaimed, and perhaps single-dig it again. The methodology does take some time and, speaking from personal experience, a lot of patience. However, by using this technique properly, you can successfully reclaim your garden area and start fresh. You can always use the year in between to really take the time to design and plan the ideal garden you will enjoy for years to come.

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