The easiest and most inexpensive way to improve your food garden is crop rotation â€“ making sure each plant group grows in a different spot from where it spent the previous year.
It confuses and starves over-wintering pests â€“ when they emerge in spring, their food supply is gone.
Crop rotation also reduces fungal diseases. For instance, tomato blight spores spend winter months in the soil and re-activate when watering splashes infected soil up into tomato plants.
Though blight spores can drift from tomatoes in neighbouring gardens, transmission over a distance is chancier, and depends on summer rain.
But avoiding planting tomatoes where tomatoes were before is not the whole story. Potatoes, eggplant, and peppers belong to the same family (Solonaceae) and can also catch tomato blight, though peppers are less susceptible than potatoes.
Other plant families have their own diseases and pests which they transmit to their relatives in the same family, but not to members of other families.
One such family includes cabbages, radishes, and turnips. Beans and peas also share familial relations. Onions, shallots, and garlic are in another family group. Beetroots, carrots, and parsnips are all related. Squash, zucchini, and cucumber share another family grouping.
Each family has its own susceptibilities to various infections.
To people with very little space, such as a two-container veggie garden, crop rotation is challenging, but even a two-year rotation is better than nothing.
Luckily, there are ways of improving it. You could change the top few inches of soil each year, and move one container further away from the other. An alternative is growing a different food family each year for three or four years.
Most vegetables now have container-friendly compact forms.
A three-year crop rotation can be manageable if compost is added to garden beds each year â€“ though a four-year rotation is betterâ€¦ or even five years, if potatoes and tomatoes can be added into the rotation cycle.
Because itâ€™s really easy to forget where vegetables were planted, it helps to draw a rough sketch of your veggie garden. Then add plant names in their previous-year places.
Itâ€™s helpful to add the names during the year, before you file it away. It will help when you want to figure out rotation for the coming year.
Gardeners whose veggie garden is in-ground donâ€™t necessarily have to add lashings of compost or manure yearly in every food-growing spot.
Adding more compost to food crops is seldom a mistake â€“ but itâ€™s hard to make enough compost and very easy to use it all too quickly.
Thatâ€™s why itâ€™s worth knowing that some crops help feed other crops.
Peas and beans absorb nitrogen from the air and store it in little root nodules which enrich the soil for later crops.
Cabbages and other leafy crops love growing in nitrogen-rich soil, so they are a good choice to follow the peas and beans (plus compost, if possible).
Root crops are good for the third-year spot, because most arenâ€™t big eaters. They can include turnips, carrots, parsnips, and beets.
But if beets are grown for leaves, as well as roots, you get better leaves with higher-nitrogen soil.
Crops that need rich food include squash, tomatoes, cucumbers, corn, asparagus, kale, and all of the cabbage family.