Can You Plant Bush Beans After Onions?

General Advantages

• With crop rotation, you avoid growing the same plants -- or plants within the same families -- year after year, opting instead to "rotate" the plants to different beds. The advantages of crop rotation are plentiful. Because many of the insects that feed on members of the same plant family tend to lay eggs in the soil, they can cause problems the next season, unless you rotate crops. Fungal spores and bacteria can also overwinter, which is another good reason to "confuse" these plant diseases by establishing plants from a different family each year.

Specific Advantages

• Bush beans and other legumes contribute nitrogen to the soil. Setting them in different beds throughout the garden as the years go by helps enrich different parts of the garden. In addition, bush beans don't suffer from the same diseases and pests as onions. Onions are prone to thrips and maggots, as well as fungal diseases like downy mildew and root rot. Bush beans are more often plagued with spider mites and Mexican bean beetles, as well as diseases like bean mosaic disease and bacterial blight.

Succession Planting

• In some cases, you may want to follow an onion planting with a bean crop in the same year. Onions are best planted in the garden in early spring, and will be harvested in late summer, three to four months after planting. After removing the onions, turn the soil to improve texture, and then plant bush beans for a fall crop. If the onions mature late and you are concerned about beating the frost, choose a quick-maturing bush bean variety, such as "Top Crop" or "Tender Crop," which are ready for harvest in about six weeks.

Annual Planting

• If you choose to have one kind of vegetable in the same bed during the entire growing season each year, your crop rotation schedule is even easier to plan. After planting onions the first year, follow with bush beans the second year. Because they mature within six to eight weeks, you can raise two or more crops of beans in the same bed in the same growing season.

Best Crop Rotation Plans

• If you have enough beds to keep rotating crops, it's helpful to avoid alternating beans and onions each year, so that three to four years pass between crops of the same family. That way, diseases like mosaic bean virus will have died off before beans are planted again. Similarly, onions won't have to contend with downy mildew or root rot if three to four years pass between Allium crops in the same bed. Solanaceae family vegetables such as tomatoes (Solanum lycopersicum), peppers (Capsicum annuum) and eggplant (Solanum melongenaare) are perfect for following beans, because they are all heavy feeders that benefit from the nitrogen that beans add to the soil. In year four, grow members of the Apiaceae, Brassica or Cucurbita families.