Seasonal Companion Planting for the Southeast Garden: What to Plant With What, Month by Month

Companion planting works best when it follows the season. The plants you pair in March are not the same plants you pair in July. Crops have different pests, different growth habits, and different needs depending on the time of year.

If you plan your companion planting by season, you get pairings that actually match what is growing at that time. This is easier than trying to remember dozens of chart entries, and it is more useful because it matches the real rhythm of a Southeast garden.

This guide covers companion planting for every major growing window in the Southeast, with specific pairings for cool-season and warm-season crops, and a practical plan you can follow from March through November.

The Cool Season: March Through May

This is when many Southeast gardeners start their first planting. Cool-season crops are at their peak, and the companion planting strategies are mostly about pest protection and space management.

March: Early Starts

Carrots with alliums. Plant carrots alongside onions, garlic, or chives. The alliums mask the carrot scent from carrot fly, which is one of the most reliably proven companion plantings in the literature. Use alternating rows or interplant every fourth carrot row with alliums.

Peas with radishes and turnips. Peas do not have many serious pest problems in the cool season, but planting them alongside radishes and turnips creates a dense ground cover that suppresses weeds. The radishes mature quickly and can be harvested before they crowd the peas.

Lettuce with garlic. Lettuce benefits from the pest-deterrent effect of nearby garlic. Plant garlic around the perimeter of lettuce beds or interplant every few lettuce heads with a garlic clove. This is especially useful in the Southeast, where spring heat can arrive early and stress lettuce if not shaded or protected.

Spinach with strawberries. If you have established strawberry beds, let spinach grow underneath the strawberry foliage in early spring. The strawberries provide light shade that keeps spinach cool, and the spinach covers the soil between strawberry plants, suppressing weeds until the strawberries fully leaf out.

April: Main Cool-Season Planting

Broccoli and cabbage with rosemary and sage. Herbs like rosemary and sage produce strong aromas that help confuse pests that find brassicas by smell. Plant these herbs around the perimeter of your brassica beds. They also bloom in spring, bringing in beneficial insects at a time when many gardeners are not yet thinking about flower plantings.

Kale with dill and cilantro. Allow dill and cilantro to flower near your kale. The flowers attract parasitic wasps that control cabbage loopers and other caterpillars. If you want to eat the dill and cilantro, harvest them for cooking but leave some plants to bolt and flower. The flowers are where the pest control benefit comes from.

Cabbage with nasturtiums as a trap crop. Plant nasturtiums on the upwind side of your cabbage patch. Aphids strongly prefer nasturtiums over cabbage. The aphids will colonize the nasturtiums, concentrating them where you can manage them instead of on your main crop. This is a proven trap cropping strategy.

Beets with onions and chives. Beets can suffer from beet leafhopper, and the sulfur compounds in alliums help disrupt this pest. Plant alliums on the border of beet beds or interplant them within the row.

May: Transition Month

May is the bridge between cool and warm season in the Southeast. Some cool-season crops are finishing, and warm-season crops are going in. This is a good time to plan companion pairings for both.

Cool-season carryovers with flowers. As lettuce and spinach begin to bolt from the heat, scatter alyssum and zinnias among them. The flowers attract beneficial insects that will stay in the garden when the warm-season crops arrive.

Warm-season early plantings with basil and borage. If you have transplanted tomatoes or peppers into the garden, plant basil around them. While the claim that basil improves tomato growth is not strongly supported by research, basil does attract beneficial insects and provides ground cover that suppresses weeds. Borage attracts pollinators and is believed (though not conclusively proven) to improve tomato flavor.

Bush beans with marigolds. Plant marigolds between bean rows. While the nematode-suppression benefit only works when marigold roots decompose into the soil, the flowers do attract beneficial insects that control aphids and other bean pests. Turn the marigolds under at the end of the season for the nematode benefit.

The Hot Season: June Through August

This is when companion planting becomes most important in the Southeast. Heat stress, pests, and weeds are all at their peak. The right companion pairings can make a real difference in garden productivity during these difficult months.

June: Warm-Season Established

Squash and zucchini with Blue Hubbard as a trap crop. Squash bugs and squash vine borers are major problems in the Southeast. Plant one or two Blue Hubbard squash plants at the perimeter of your garden, especially on the upwind side. These pests strongly prefer Blue Hubbard over summer squash, concentrating them on the trap plants where you can manage them. Check the Blue Hubbard regularly and remove any squash bugs you find there before they spread.

Cucumbers with radishes. Flea beetles prefer radish foliage over cucumber leaves. Plant radishes around cucumber rows and harvest them before they mature, or let them go to seed if you want the flowering benefit for beneficial insects.

Eggplant with borage and basil. Borage attracts pollinators, which eggplant benefits from since eggplant flowers can be difficult for some bees to access. Basil provides some pest confusion benefit, though its primary value here is ground cover and weed suppression between eggplant plants.

Corn, beans, and squash (Three Sisters). If you are growing enough space for the Three Sisters, June is when you should plant the beans after the corn is established. The corn provides climbing structure, the beans fix nitrogen for the heavy-feeding corn, and the squash spreads between the corn stalks to shade out weeds and conserve soil moisture. This system works exceptionally well in the Southeast, where the long growing season gives the squash plenty of time to cover the ground.

Tomatoes with carrots between rows. In between your tomato rows, plant carrots. The allium-like sulfur compounds in carrots help confuse carrot fly, and the carrots make good use of the space between tomato plants without competing for the same nutrients. This also helps suppress weeds in an area that might otherwise go bare.

July: Peak Heat and Pests

July is when companion planting is not just helpful but often necessary in the Southeast. The heat, humidity, and pest pressure are at their highest.

Melons with radishes and nasturtiums. Melon vine borers and cucumber beetles are serious threats to melons. Plant radishes on the perimeter to distract flea beetles, and plant nasturtiums as a trap crop for aphids. Both strategies work best when the trap plants are on the upwind side of the melon patch.

Sweet potatoes as a living mulch. Plant sweet potatoes around the base of larger warm-season crops like peppers or eggplant. The sweet potato foliage spreads quickly and shades the soil, reducing evaporation, suppressing weeds, and cooling the root zone of neighboring plants. This is not a chemical interaction, it is purely physical — but it is one of the most effective companion plantings in the hot season.

Okra with basil and marigolds. Okra is relatively pest-resistant, but planting basil and marigolds around it helps with general pest confusion and beneficial insect attraction. Marigolds turned under at season end will also provide nematode suppression for the next year's planting.

Soybeans with sunflowers. If you are growing soybeans, plant sunflowers at the border. Sunflowers attract birds and predatory insects that help control bean pests. The sunflowers also provide a visual landmark in a large garden, which is useful when you are scouting for pests during the hot months when everything grows fast and pests multiply quickly.

August: Late Warm Season

August is when warm-season crops are at their peak and you start thinking about fall planning.

Late tomatoes with basil and borage. Your late tomato plants will benefit from the same companion plants as early tomatoes. Keep the basil growing and let the borage flower. If the borage has self-seeded around the garden, that is a bonus — it will be there to support beneficial insects next season without any replanting.

Fall garden prep: sow cover crop companions. In late August, start thinking about your fall garden and what to plant alongside it. This is a good time to sow a cover crop of winter rye or hairy vetch in empty beds. In spring, these will be turned under to provide nitrogen and organic matter for your warm-season crops. This is a form of companion planting that spans seasons — one crop feeds the next.

The Cool Season Returns: September Through November

The Southeast gets a second growing season in the fall. The companion planting strategies for fall are similar to spring, with a few seasonal adjustments.

September: Fall Planting Starts

Fall carrots with alliums. The same carrot-onion strategy works in fall planting. Fall carrots often have better flavor and less pest pressure than spring carrots because carrot fly populations tend to be lower in the fall.

Fall brassicas with rosemary and sage. The same herb companion strategy works for fall cabbage, broccoli, and kale. The herbs also overwinter in the Southeast and will provide benefit again next spring.

Cover crops as companion plants for next year. Fall-planted hairy vetch, crimson clover, or winter peas are companion plants for next year's garden. They fix nitrogen, build organic matter, and suppress weeds during the dormant season. Turn them under in spring to feed your tomatoes, corn, and peppers.

October: Cool-Season Main Planting

Fall spinach with garlic. Garlic planted in October will overwinter in the Southeast and be ready to harvest in spring. Plant garlic near fall spinach rows for pest protection. The garlic also provides a visual boundary in beds that may be mixed with other cool-season crops.

Fall lettuce with chives. Chives are perennial in much of the Southeast and will return every year. Plant them around lettuce beds where they will provide consistent pest protection for both fall and spring lettuce crops.

November: Wind-Down

November is mostly about finishing and planning. There is not much companion planting to do, but you can make notes now for next year.

Observe what worked. This is the most overlooked companion planting step. Watch which pairings kept your plants healthy, which areas had the most pest pressure, and which combinations you want to repeat. Write it down. Companion planting is partly science and partly observation — the evidence tells you what works in general, but your garden will have its own specific dynamics.

Companion Planting Mistakes to Avoid

Planting companion plants you do not need. If you have no pest problems and your plants are growing well, do not add companion plants just because a chart says you should. Companion plants should solve a specific problem or serve a specific purpose, not exist for their own sake.

Forgetting that companion plants compete for resources. Every plant in your garden takes water, nutrients, and light. If you add companion plants without accounting for their own needs, you may end up with two struggling plants instead of one healthy one. Make sure your companion plants are smaller or less resource-demanding than the crop they accompany.

Ignoring the seasonal timing. Planting a companion flower that blooms in July does you no good in March. Match your companion plantings to the active season of your main crops. If the companion plant is done before the main crop needs it, it is not a good pairing.

Overcomplicating the garden. The best companion planting plan is one you can actually follow. Start with two or three strategies and build from there. The carrot-onion pairing alone covers a huge chunk of what most gardeners need.

A Practical Monthly Checklist

Here is a quick reference for what to do each month in the Southeast:

March: Carrots with alliums. Peas with radishes. Lettuce with garlic.

April: Brassicas with rosemary and sage. Kale with flowering dill. Cabbage with nasturtium trap crop.

May: Tomatoes with basil. Bush beans with marigolds. Scatter alyssum and zinnias.

June: Summer squash with Blue Hubbard trap crop. Cucumbers with radishes. Start Three Sisters if space allows.

July: Melons with radish and nasturtium trap crop. Sweet potatoes as living mulch. Okra with marigolds.

August: Late tomatoes with basil. Plan fall cover crops. Take notes on what worked.

September: Fall carrots with alliums. Fall brassicas with herbs.

October: Fall spinach with garlic. Plant perennial chives near lettuce.

November: Finish observations. Plan next year's companion planting layout.

The Bottom Line

Companion planting is not a grid of green checks and red Xs. It is a seasonal practice that changes as your garden changes throughout the year. The pairings that matter in March are different from the pairings that matter in July. The strategies that work in a small backyard garden are different from the strategies that work in a half-acre plot.

Start simple. Plant carrots with onions. Put a trap crop on the perimeter. Scatter flowers between vegetable rows. Turn under legumes at season end. Watch what happens. Adjust next season.

The garden will tell you what works. Your job is to listen.

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— C. Steward 🥕