Experimenting with Diversity


Written By

Tatiana Schreiber

Written on

September 01 , 2007

Ever since I was in grade school and heard about Gregor Mendel and his famous hybrid sweet peas, I’ve been fascinated with the notion of conducting experiments with plants in a garden. Of course Mendel really was a scientist, while I’m something between an enthusiastic gardener and a tiny-scale farmer. I don’t expect my own experiments will yield anything as ground-breaking as the laws of heredity, but I always hope they will prove valuable in guiding my work the following year. And besides, they’re really fun! 

The most dramatic outcome of last year’s experiments was this year’s cucumbers. I had the best cucumber crop ever, in one part of my garden, while another planting nearby barely produced at all. The vines were stunted and yellow despite my side-dressings with dried chicken manure and my foliar feedings with compost tea. What caused the difference?


Both crops had about the same amount of light, and were in the same garden, but the beautiful, bountiful crop was planted in beds that had nurtured my tomatoes last year-¾tomatoes with an underplanting of hairy vetch. I had heard about the vetch/tomato intercropping idea a couple of years before, and it was my second year using that method. The idea is to place your tomato transplants in the ground and then undersow the vetch as a living mulch. Theoretically, the vetch helps control the spread of bacterial and fungal diseases which can be transmitted from the soil onto your tomato plants when it rains. And since vetch is a nitrogen-fixing legume, it is thought to supply some nitrogen to your tomatoes.

Farmers around the world have interplanted legumes with other plants on the theory that the legumes benefit the other crop, but I haven't yet been able to determine whether the vetch has really helped my tomatoes. I’ve had just about as much early blight in the tomatoes planted with vetch this year and last as in years when I used hay mulch. But the vetch certainly worked as mulch, shading out other weeds. The most obvious benefit was to those cucumbers, though. This spring I pulled out the dead vetch from the year before, adding it to the compost of course, and planted the cucumbers. I added no other soil amendments to these beds except some compost in the trenches where I planted the cucumbers. Lush, dark green, productive vines (of several different varieties) were the result.

The less successful cucumbers included some of the same varieties. They were planted in the same garden, but along the edge in order to grow up the fence, in a spot that had seen only hay mulch the year before. The result: stunted, yellow, cucumbers which produced very little. I'm not sure yet why the second site was quite so bad, but I'm now confident that using vetch the year before is good for cucumbers!

What else have I learned from my experiments? Well, this year I went a little overboard with intercropping "field trials." My hypothesis is that the more diversity one can introduce into the garden the better, so this year I decided to use both vetch and crimson clover as the living mulch under alternating rows of tomatoes.  I also used clover as mulch under all my summer squash, winter squash, and melons. clover, like vetch, can add significant nitrogen to the soil as well as organic matter when it gets turned in. How will the tomatoes, squash, and melons be affected? So far, the jury is still out, but it's clear that no harm was done. My summer squash were wildly abundant, weeds were non-existent, and disease seemed to arrive late in the summer squash patch.

As to comparing clover to vetch, I really haven't noticed a difference. All my tomatoes did eventually suffer from early blight or other bacterial or fungal diseases, and differences between the degree of damage seemed more due to the variety (i.e. the resistance of the plant itself) than to the type of interplanting I did. (An intriguing finding, however, is that one tomato plant, surrounded on all sides by amaranth that I'd let grow for color, was the most disease free of all the tomatoes in my garden.)

Farming and gardening are inherently risky activities- you never know what the weather will bring, how your new varieties will bear, or whether you'll be able to outsmart the raccoons (unlikely)! But the more you experiment, observe, and¾importantly¾document your results, the more you can manage the risk with a degree of fortitude or, even better, a spirit of adventure. It’s an interesting challenge to consider your garden as a site for investigation.

This year's experiments resulted in wonderful color and abundance in my gardens¾though my beautiful cucumbers finally succumbed to something viral in September. Instead of dwelling on that, however, I'm already thinking about next year. Maybe I should try soybeans as an undercrop with the corn?

About the Author

Tatiana Schreiber

Tatiana Schreiber

Tatiana Schreiber is a research associate at Rich Earth Institute in Brattleboro, and also consults on complementary plants for growing with solar arrays. She teaches ecological agriculture at local colleges and grows heirloom and unusual garden seedlings including medicinal plants at Sowing Peace Farm in Westminster West.

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