Former Lawrence City Commissioner Bob Moody, who has more time these days to putter in the vegetable garden he plants in that rich soil north of the Kansas River, called recently to request "the definitive article on companion planting."
We aim to please.
What Bob is referring to might better be termed interplanting. The idea is that by mixing vegetables and interspersing various flowers and herbs, you can inhibit pests and disease and eliminate the need for chemical deterrents. You also can improve the quality of your crops by planting certain vegetables in proximity to others.
As you might guess from such a description, this is a method that has been embraced by the organic gardening community.
Before you worry about companion planting, however, you need to be practicing a couple of other gardening principles. For starters, mulching and amending with finished compost will improve the quality of your soil and provide the nutrients and organism activity necessary for producing healthy crops.
Second, some form of crop rotation is a must. This can be tricky in a small home garden, where it is impossible to plant this year's tomatoes a quarter of an acre away from the site of last year's crop, but at the very least you need to give it a shot. Nightshades (particularly tomatoes, potatoes and eggplant), corn and cole crops should find a different home every year. The diseases and insects they attract overwinter in the soil, and replanting the same crop in the same spot simply saves them the trouble of seeking out a new target when the next garden comes up.
Crops also require differing amounts of nutrients and a specific site is unlikely to be able to support the same vegetable for more than a couple of years.
As for the specific practice of companion planting, the best resource I have seen is Rodale's "All-New Encyclopedia of Organic Gardening," which approaches the issue in four ways: enhancing the growth of one crop by planting it next to another; using one kind of vegetable to trap pests that would otherwise harm your garden; using aromatic plants to repel pests; and providing host plants for beneficial insects, which prey upon pests.
I'll deal with the first two approaches this week, and the other two next week.
The easiest way to improve productivity in your garden is to pay attention to where you locate vegetables that fix nitrogen into the soil: namely, legumes. If you alternate double rows of peas, beans or peanuts with double rows of other row crops, the legumes' neighbors will benefit from the additional nitrogen in the soil. Think ahead, though. You don't want to plant bush beans between rows of corn. for example. The corn will throw enough shade to stunt the growth of the low-growing beans. Plant pole beans near taller crops.
The idea of using companion planting to trap pests is one that requires a little strategic planning as well. Radishes planted alongside carrots and other roots crops often will draw nematodes. Because radishes mature faster, usually in 21 to 30 days, they are more inviting at least initially than slower-growing crops. Stagger your seedings of radishes so they will mature at intervals and then pull each planting on schedule.
This is one of those win-win gardening tricks. If your radishes emerge riddled with nematodes, then the plan worked; if your radishes show no presence of nematodes, then you have a nice crop of radishes to eat. Radishes that have been contaminated by nematodes should not be tossed onto the compost pile but should be disposed of separately and not returned to the garden as waste.
Next week: Aromatic controls and attracting beneficial insects.