Corn can indeed be grown in containers provided the container can accommodate a dozen plants per pot sown 4 inches apart. Corn despises peas but loves mustard greens, beans, squash, pumpkins, cucumbers, melons and our entire companion group. Three large containers would allow three successive sowings two to four weeks apart. You can also select three varieties with three different maturation dates to extend the season. But note that they will cross-pollinate and the resulting seed will be hybrid.
Native Americans often planted corn, squash or pumpkin, and pole beans together in the same hill with either clams or fish heads. The pole beans climbed the corn and the squash meandered around the base, a good water conservation technique. The method also suggests that fish fertilizer might well be the key to this group’s health. Corn is a heavy feeder.
Practically speaking you would need a huge container and we should probably think in terms of a collection of several. We have used beans and cucumber in other groups so perhaps we can eliminate them for now. Squash, pumpkin and melons each require a minimum of five gallons of soil per one or two plants. So if a balcony garden is what you have I wouldn’t plant them in with your corn but instead add some companion flowers and mustard greens while planting squash, pumpkin and melon each in their own pots. Pre-soak corn seed for 24 hours before planting. Containers should then be covered with wire or floating row cover until your corn is about 6 inches tall. The birds will gladly eat your seed if you don’t.
An added companion for squash and pumpkin is radish. Sow the seed right in the same hill. Melons love morning glories and the same thing should be done. Squash, pumpkin, and melon can be easily trained to grow vertically by tying the vines to a trellis as they grow. This allows for some of the companion group in the foreground.
I think this collection is particularly lovely. Corn is worth growing for its beauty alone. Squash, pumpkin, and melon are as pretty as it gets with large exotic leaves and gorgeous flowers. Add some dill, African marigolds, nasturtium, maybe a few petunias. With morning glory and the dancing sprays of pink radish flowers I can’t imagine what could be more beautiful.
Keep in mind that your container must be large enough to accommodate 12 plants. Pre-soak corn seed and plant two inches deep, three seeds per hole, four inches apart on your last frost date. You might be able to plant a little earlier provided your container is covered with floating row cover. Rather than successive sowings every two to four weeks consider several varieties with varying maturation dates from 60-100 days. They will however cross-pollinate and the resulting seed will be hybrid. Add some mustard greens to your corn planting. They are cool weather crop and might well succumb to the heat eventually but are an important companion to corn. Direct sow mustard seed in your prospective corn containers up to six weeks before your last frost date, about 1/4th inch deep, 4 inches apart. Be sure to mark where your corn seeds will be planted later.
Pumpkin and squash can be started indoors 3 to 4 weeks before your last frost date but I don’t recommend it unless you have an extremely short growing season. Pumpkin and squash starts are fragile and don’t transplant very well. Direct sow 2-3 seeds per hole, one inch deep. Once germinated thin to one plant per hole. Do not pull them out but rather clip them off. Pulling them out might damage the roots of the one you keep. Each plant requires 2½ gallons of soil when container grown. The length of time to mature varies. Pumpkins require 70-120 days. Summer squash requires 45-65 days and winter squash 80-110. Please note that unless you entirely lack any garden space this family is so undemanding that it can be cultivated anywhere. They are however gorgeous in containers. Long vines can be trained on trellises and bush varieties have spectacular foliage. And by the way, melons are extremely heavy feeders and must be watered frequently. They too can be trained to grow vertically.