Tomatoes will protect asparagus against the asparagus beetle. Since they are tender plants, put tomatoes in during late spring after the early crop of asparagus spears have been harvested. Tomatoes and all members of the Brassica family repel each other and should be kept apart. Tomatoes protect gooseberries against insects.

Tomatoes are compatible with chives, onion, parsley, marigold, nasturtium and carrot and for several years I planted garlic bulbs between my tomato plants to protect them from red spider mites.  Though not containing fungicidal elements, tomatoes will protect roses against black spot.

The active principle of tomato leaves is solanine, a volatile alkaloid which at one time was used as an agricultural insecticide.  To make a spray for roses: Make a solution of tomatoes leaves in your vegetable juicer, add 4 or 5 pints of water and a tablespoon of cornstarch.  Strained and spray on roses where it is not convenient to plant tomatoes as companions.  Keep any unused spray refrigerated. Tomato juice will neutralize the odor of butyl mercaptan, the defense spray of the skunk.

Unlike most other vegetables, tomatoes prefer to grow in the same place year after year, and this is all right, unless  you  have a disease problem, in which case plant your tomatoes in a new area. Stinging nettle growing nearby improves their keeping qualities and redroot pigweed, in small quantities, is beneficial, too.  Since that re heavy feeders give them ample quantities of compost or decomposed manure. Mulch and water in dry weather to maintain soil moisture and stave off wilt disease and blossom end rot.  But never water tomatoes from the top. Water from below and water deeply. Tomatoes are inhibited by the presence of kohlrabi and fennel.

Root excretions of tomatoes have an inhibiting effect on young apricot trees and don't plant tomatoes near corn, since the tomato fruitworm is identical with the corn earworm. Don't plant near potatoes, either, since tomatoes render them more susceptible to potato blight.

If you smoke, be sure to wash your hands before you work in your garden, for tomatoes are susceptible to diseases transmitted through tobacco.