The best cover crop for tomatoes depends on what your soil needs most. French marigolds fight nematodes in your beds. Crimson clover adds nitrogen. Both crops improve your soil before you plant your tomatoes in spring.
I grew French marigolds as a cover crop in my worst garden bed for two summers in a row. The bed had root knot nematode problems that stunted my tomatoes for years. After two months of dense marigold growth each season my tomato roots came out clean with no more galls.
Florida IFAS research found marigolds must grow thick to kill nematodes. You need to plant them close and let them grow for at least sixty days before you turn them under. Quick plantings of a few weeks do nothing to reduce nematode counts in your soil.
The French marigold types that work best include Tangerine, Single Gold, and Goldie. These release chemicals from their roots that kill nematodes in the soil. African marigolds look nice but do not suppress nematodes as well as the French types.
Crimson clover works great when you need more nitrogen for your tomato rotation crops. This legume fixes nitrogen from the air into a form your plants can use. Plant it in fall and turn it under three weeks before you transplant tomatoes.
Winter rye serves as another solid choice for soil preparation tomatoes need in spring. It grows fast in cool weather and adds organic matter when you till it in. The thick roots also break up hard soil and improve drainage in your beds.
I tested crimson clover one fall and saw my soil improve by the next season. The clover grew eight inches tall by early spring and added a nice boost of green matter when I turned it under. My tomato plants grew darker green leaves that year without any extra fertilizer.
Time your cover crop kill date right for best results. Turn under your cover crops at least two to three weeks before you plan to plant tomatoes. This gives the green matter time to break down so it does not steal nitrogen from your young plants.
You can mow your cover crop first to make tilling easier in your beds. Chop it into small pieces and work it into the top six inches of soil. Water the bed after tilling to speed up the breakdown before your tomatoes go in the ground.
Read the full article: Companion Planting Tomatoes: Proven Plant Pairings
