My most successful year for both corn and pumpkins, without a doubt, was '78. That was the year I planted the two of them together. Never was my Golden Queen sweeter or more prolific; never were the pumpkins larger and more numerous.
In early June of that year I plotted a 16-by-30-foot area at the very end of my garden. I dug several shallow rows along the 30-foot length and planted the corn densely, every few inches or so. I pulled a little soil over the seeds and added a couple of inches of manurey straw over the entire area. Then I turned, for the next few weeks, to other parts of the garden. Toward the end of June I realized I was running out of large areas in which pumpkins could roam. The only big plot left was the one in which the corn was planted, and by then the young seedlings were a good six inches tall. I planted six pumpkin seeds among the corn, each as far from the next as possible. All germinated within a few days.
As the corn grew tall, the pumpkins rambled all about and even climbed the cornstalks. The dappled shade on the ground seemed to make the pumpkins very happy. Harvesting the corn in late August and early September was a little tricky because of the pumpkin vines all over the ground, and a few did get bruised under my feet, but with a little care the damage was minimal. I left the cornstalks where they were after harvesting, because they supported many of the pumpkin vines. As the cornstalks dried, the thick canopy of leaves disappeared and allowed the sun down, painting the green pumpkins lovely shades of orange. By October, the pumpkin crop was ready to bring in.
If you want to try this, both pumpkins and corn can still go in this year. In fact, both can be planted until mid-July and still produce good crops.
This practice of intermingling crops in a row or bed bears the lofty name of multi-crop and is ideally suited for small gardens where space is at a premium. My experience with multi-crops is that they're better suited for wide-row or raised-bed planting than the traditional garden layouts that call for long, single rows. Each crop needs ample space to spread out, up and down.
Compatible vegetables are ones that have different growing habits. The corn/pumpkin combination, it turned out, was an obvious one because one grew along the ground and the other grew tall. Pole beans do well when grown with corn because the beans fix nitrogen in the soil for the nitrogen-gobbling corn, and the beans can grow up the cornstalks. Vines don't seem to hinder the corn's progress at all.
Lettuce and other low-growing greens do well with small root crops, such as beets, radishes and onions. When growing multi-crops such as these, the seeds can be mixed together and then broadcast in the wide row or bed before being covered over. Cucumbers, if offered a trellis to climb, can be interplanted with bush beans, peas or radishes. More than two crops can be planted in the same place.
Some vegetables don't lend themselves to multi-crop planting. Tomatoes, for example, require enormous amounts of space and shouldn't get too close to anything because they grow so large. Cabbage and broccoli, too, will quickly push out crops close by, but if you give them plenty of room, you can surround them with, say, a frame of onions, which is supposed to repel the white cabbage moth. It's also a good idea to find out what don't do well when grown together. But so far, I haven't found a crop that actually damages another, as long as the plant's normal growing habits are taken into account.
A good book that helps pinpoint potential problems and offers advice on companion planting as an insect deterrent is "Carrots Love Tomatoes" by Louise Riotte, Garden Way Publishing, Charlotte, Vermont 05445, $6.95, available in bookstores.