Last Sunday, I wrote a column about growing pumpkins and winter squash. In it, I mentioned covering the surface of the beds with red plastic in order to help warm up the soil. I've since gotten a few e-mails from readers asking for more details about using the red plastic mulch.
This coming Sunday, I'll be mentioning it again in my column on growing tomatoes so it looks like it would help to fill you in a bit more on how this works.
Warm-season crops are veggies like tomatoes, summer squash, pumpkins, eggplants, peppers, cucumbers, corn, beans and winter squash. Because they are heat-lovers, we plant them after the danger of frost is past, which is usually after May 15th. Many folks wait until around June 1st.
Anything we can do to give them toasty-warm soil to grow in makes a big difference in how successful and productive these veggies will be. That's where the plastic comes in, although I should mention that I don't use it for corn or beans.
For years, I've known this and experimented with both black plastic and clear plastic. While both are helpful in this regard, the red plastic works even better.
It's been on the market for several years now. Research shows that the red spectrum reflects more light up into the plants, which is a good thing as Martha Stewart would say. After using it for the first time, I discovered my plants were about 30% more productive. That's quite a difference. I've used it annually ever since.
The red plastic mulch looks a bit like a cheap picnic tablecloth and comes in sheets. It is much easier to locate at local garden centers like Northwest Seed & Pet and online than it used to be. Mail-order sources for it include Gardens Alive!, Johnny's Selected Seeds, Totally Tomatoes, Lee Valley Supply, Peaceful Valley Farm Supply, Harris Seeds and so on. Nowadays, you can pretty much find it anywhere. Go to my "Links" page for links to the web sites of these companies and more.
Our raised beds are watered by soaker hoses that are laid directly on the soil surface. To use the red plastic mulch, place the plastic over the soil surface -- as well as over your soaker hoses or drip irrigation system if that's what you have -- and then weight it down so it won't blow away. My husband Bill made me some metal pins to hold it down but you can also use boards, bricks or rocks around the edges to hold it down.
When you're ready to plant, just cut a little "X" into the plastic and plant the seedling directly through the "X." It's a little bit of a hassle doing it this way but it will be well worth it when you see how productive this method is!
Unfortunately, the red plastic rarely holds up well enough after a season to use it again the following year, especially if you use metal pins to hold it down.
One other thing I should mention is that I've rarely used any kind of plastic on the soil of the beds where I grow summer squash like zucchini and crooknecks. I experimented with using plastic on one bed and no plastic on the other one year and did not notice any difference between the plants in the two beds. So why go to the extra hassle and expense of applying plastic if it's not necessary?
I hope this information is helpful to you and clears up any confusion of how this red plastic mulch works. There are also plastic mulches that come in silver or green, and they are supposed to help improve production, but I haven't had any experience with them so am unable to make any suggestions.