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Weeds Weeds and more no Weeds

Like everyone else I want to spend less time on weed control in the pumpkin patch. There are lots of methods in use from letting them grow, mulching, plowing/tilling, hoeing, pulling, and chemicals. Each has its advantages and disadvantages. Most take a lot of time. I would like to spend less time on weeds so I can do other things in the pumpkin patch.

In 2004 I tried an experiment to see if it would be possible to use a passive method to control weeds. I covered a large area of one patch with thin, cheep clear plastic. To hold it in place so it doesn't blow away and keep the heat in, I use patch soil on all the edges. A thermal probe under the plastic was used to monitor the temperature. Its no surprise that when the sun comes out the temperature under the plastic rises very fast. Under strong sunlight the temperature was 92 while the outside air temperature was 68 in just a short while. I have seen the temperature go to 130+.

Small weed seedlings are no match for this environment and they quickly wilt. The question for me was how long do I need to leave the plastic in place to be effective. I know from past mistakes that leaving clear plastic on the lawn for a couple hours is enough to cause serious brown spots that are slow to recover. In this case we want no recovery. I want them dead, real dead so I left the plastic on for a week. When the plastic was removed there was nothing growing except around the outside of the plastic. This worked so well I decided to move the plastic to the other patch, which had been growing weeds for the week. Here the weeds were already more developed and most have fully developed true leaves. These turned out to be a bigger challenge for the weed cooker method. Although its a week later and the sun is stronger the weeds were much more resistant to high temperature. They did not wilt as fast and would partially recover overnight. This plastic was on the a part of the patch opposite the pumpkin plant so there was a lot of time before it needed to be removed. Eventually the weeds would lose the battle against the daily high temperature. When this plastic was removed I could see where some of them had continued to grow and produce several leaves but most all were dead.

2005 was my first try to put this method into practice. I now knew I needed to put the plastic down before the weeds can develop true leaves. Previously I thought I would be able to recycle the plastic from year to year but the UV light is too much for it. So this year I bought the cheapest thinnest plastic drop cloths I could find. Sometime in the spring after all the patch prep is done and before its warm enough for weeds to start I lightly water the entire area and put the plastic down. With a little preplanning I was able to place the plastic so it could be peeled back away from the pumpkin as it grows while keeping the rest of the area covered. 6 to 8 feet were left as a buffer zone between the plastic and the advancing vines. I left a space between the sheets for walking boards, which allowed me to get to the plants. There will always be a few weeds to be removed by hand around the edges and between the sheets. It's a great feeling to finally remove the plastic and have bare soil. The leaf canopy of the plant keeps most of the area free of weeds and the few that do grow are very slow and easy to remove before they get very big.

Pros

On the up side this method has saved me a lot of time, which is better spent on other task.

The clear plastic helps warm the soil in early spring. I don't think the high soil temperature is a problem for pumpkin roots. Even though the surface gets very hot the temperature does not penetrate very deep. The surface layer of soil will naturally repopulate.

The soil is not disturbed so no fresh weed seeds are rotated to the surface to germinate.

Pumpkin plant roots are not disturbed.

Patch looks great.

Cons

Nothings perfect. If your patch is bigger than mine it may have some practical application problems that are not apparent to me. The only negative thing for me is large areas of the patch are unavailable.

All the soil treatments must be done before the plastic is installed. Things like additional molasses will have to wait.

The plastic could interfere with your irrigation practices.