Vegetable Succession and Companion Planting

Examples of three-season successional planting schedules

The following sample planting plans can be used simultaneously in vegetable gardens with multiple planting beds.

Tips for successful succession planting

• Start seeds indoors or in a protected outdoor area. Use transplants, even for crops that are usually direct-seeded. (Direct-sowing will make it difficult for the seedlings to get established due to competition with the established plants.) You will gain several weeks of growing time by having transplants ready to go into vacated areas.
• Sow seed outdoors as soon as the soil can be prepared in spring. Or, if possible, put in transplants of cold-hardy crops instead, to reduce the risks associated with germination (seed rotting before it germinates, damping-off disease, etc.) and to take advantage of quicker crop growth and maturity.
• Plant warm-season crops as soon as the danger of frost has passed.
• Plant squash, bean, and cucumber plants when you are finished harvesting earlier cool-weather crops.
• Starting in late July, you can also sow seeds of the same crops you direct-seeded in early spring, like beets or mustard greens.

Relay planting is the successive planting of one type of crop. For instance, green beans may be planted at two-week intervals for a continuous harvest. Early crops are likely to get a slower start due to low temperatures, with later crops growing and maturing more quickly. This often results in a glut of produce at the height of the season, so be prepared to process your harvest in advance.

Crop succession is closely related to the concept of crop rotation. Crop rotation is the practice of moving crop families to different garden locations each growing season. Examples of common crop families include the tomato/eggplant family (nightshades, Solanaceae), pea/bean family (legumes, Fabaceae), and squash/melon family (gourds, Cucurbitaceae).

Rotation can help even out nutrient removal from the soil, because nutrient needs vary by crop, as does root growth and architecture as they mine the soil for nutrients at varying depths. Crop rotation can also reduce weed pressure because weeds associated with certain crops grown in particular ways can become abundant over time. Pest populations and infectious diseases can similarly build up over time if a susceptible crop is not moved to another location.

Crop rotation is an important pest and disease management tool for farmers with fields that are far apart. Although it is still a beneficial practice for home vegetable gardens, it is only marginally helpful in lessening insect and disease pressure in those settings due to the smaller scales involved.

Companion planting, which includes interplanting, is the intentional planting of two or more plant species close to one another to improve plant growth, increase garden productivity, or repel or suppress pests.

The “three sisters” intercropping system, developed by tribes of northeast Native Americans, is a good example. Corn seed was planted in a small circular pattern. Bean seed was planted at the base of the corn, and squash plants sprawled around the corn and beans. The bean plants used the corn for support and improved the soil through nitrogen fixation. The squash plants suppressed weeds and conserved moisture like a mulch, and their spiny leaves and stems made it harder for animals to feed on the corn and beans.

Considerations for selecting companion plants

• Length of time to maturity
• Growth pattern above- and below-ground (tap-rooted or tuberous versus fibrous-rooted, for example)
• Light, nutrient, and moisture needs
• Planting arrangement:
  • Alternate plants within a row (for example, basil-tomato-basil-tomato)
  • Alternate rows within a bed (a row of peppers next to a row of onions)
  • Plant various species throughout (scattered mixing)

Maximize harvest yields with companion planting

• Plant low-growing, shade-tolerant salad greens on the north side of corn, tomatoes, or eggplants.
• Plant peas at the base of tomato cages (on the north side) in early spring. When tomatoes are planted later in spring, the filled-in pea vines will act as a wind shield.
• Sow seeds for long-season (carrot) and short-season (radish) crops at the same time. Harvest the radishes before they begin to crowd the carrots.
• Plant small plants close to larger plants, like radishes at the base of broccoli.
• Sow cover crop seeds around the base of vegetable crops in late summer or early fall. The cover crop will germinate and establish while you continue to harvest.
• Attract beneficial insects by planting flowering plants near the vegetables. Annuals and perennials that produce clusters of small flowers are highly attractive to pollinators and natural enemies (predators and parasites) of garden pests. Species popular with pollinators include mountain mint (Pycnanthemum), anise hyssop (Agastache), buckwheat, and herbs that you allow to flower (especially members of the mint and carrot plant families like cilantro, basil, and dill).
• Repel and suppress pests with a border of African marigolds (Tagetes erecta), which will attract beneficial insects and may repel certain pests with chemical compounds found in its foliage and roots.

Examples of companion plant research findings

• Volatile organic compounds of alliums, basil, rosemary, lavender, dill, cilantro, and chives repel aphids and other insects or make it more difficult for them to locate host plants.
• African and French marigolds (Tagetes erecta and patula, respectively) deter soil-dwelling nematodes.
• Thyme, onion, and nasturtium help reduce caterpillar damage in broccoli.
• Nasturtium and marigolds help reduce damage from squash bugs and cucumber beetles.
• Slugs avoid mint, rosemary, and thyme plants.
• Capsaicin (the chemical giving hot peppers their heat) and garlic sprays repel the pests of brassica crops (cabbage, kale, Brussels sprouts, etc.).