4 Plants You Should Never Grow With Lettuce, Gardeners Say

Lettuce is an easy-to-grow, cool season crop that’s typically planted in spring for an early summer harvest, or in mid-summer for autumn. But while lettuce gets along with most other veggies, you may want to avoid planting it near a few common summertime crops.

Learn what experts say not to plant near lettuce and a few planting suggestions to make your garden better.

Fennel

Fennel is typically planted outdoors sometime between mid-spring and mid-summer, but it’s best to keep fennel away from your lettuce crop when planting time arrives.

“When direct sowing, don’t plant lettuce next to fennel because it might inhibit lettuce germination,” explains Andrew Miano of the Baker Creek Heirloom Seed Company.

Even if you transplant fennel into your garden as started plants, it’s still recommended to avoid growing fennel too close to lettuce or other crops. Fennel is, after all, one of the most notoriously allelopathic veggies you can find, and it can release compounds into the soil that thwart the growth of most neighboring plants.

If you give fennel enough space in the garden, it may not cause major issues. But to be extra safe, you may just want to grow fennel on its own in a dedicated raised bed, grow bag, or other roomy container.

Plant fennel next to: Not applicable; it’s best to plant fennel on its own.

Want more gardening tips? Sign up for our free gardening newsletter for our best growing tips, troubleshooting hacks, and more!

Brassicas

Cauliflower, Brussels sprouts, broccoli, and other brassicas, love cool weather and rich soil—just like lettuce. However, plant experts also recommend keeping brassicas and lettuce separate in the garden as they don’t make good companion plants either.

“Lettuce plants have fibrous roots that are fairly shallow and aren’t great at competing for sunlight or nutrients,” explains Courtney Williams of Fedco Seeds. “Brassicas share a similar root structure and are in direct competition for food and water.”

In addition to this, lettuce and brassicas can attract many of the same pests and planting these crops together can make it easier for pest insects to spread throughout your garden.

Plant brassicas next to: Alliums, chamomile, dill, celery

Summer Squash

Some growers plant a late crop of summer squash in June, July, or August to avoid pests like squash vine borers, or simply to extend their growing season. But summer squash and other cucurbits are vigorous growers that can quickly overwhelm a small garden and outcompete smaller, or slower-growing crops, like lettuce.

“These plants are heavy feeders and can compete with lettuce for nutrients,” says Miano. “Their vines can also overtake lettuce because they grow so fast.” 

If you need to grow squash and lettuce in the same garden beds, look for bush-type squash plants that don’t throw out sprawling vines, or keep your plants a bit tamer by training them to grow vertically on trellises.

Enriching your soil with compost and adding regular applications of fertilizer to your plants throughout the season should also prevent nutrient depletion and keep both lettuce and squash plants happy.

Plant summer squash next to: Corn, beans, peas, sunflowers

Parsley

Like lettuce, parsley grows best in cool weather and prefers regular watering and plenty of sun. But while parsley is often used as a pest-deterring companion plant for a variety of food crops, it just doesn’t grow that well with lettuce.

“Parsley releases chemicals from its roots that cause lettuce to bolt,” explains Miano, who suggests keeping these plants apart in the garden.

Plant parsley next to: Beans, brassicas, tomatoes, chives

What to Plant Next to Lettuce

However, just because parsley and a few other plants don’t grow well with lettuce, doesn’t mean that there aren’t a lot of excellent crops to companion plant with lettuce in mid-season. Miano recommends alliums like chives, onions, and garlic.

“Pests like aphids love lettuce, but are turned off by the pungency of alliums,” he says.

In addition to alliums, Williams offered a few more companion planting suggestions for lettuce if you’re still not quite sure what to grow near your lettuce patch.

“In the heat of summer, lettuce may benefit from growing near taller crops that provide a bit of shade,” says Williams. This can include trellised plants, like beans and peas, caged tomatoes, or even asparagus plants that throw up long, feathery fronds late in the season.

Beyond this, Williams also recommends pairing lettuce with plants like carrots and beets, or nitrogen-fixers like beans. These plants have different root systems and are less likely to compete with lettuce for space.

Even better, nitrogen-fixing legumes add nutrients into the soil that support the growth of leafy lettuce greens, while root crops break up and aerate tough soils and can make it a little easier for lettuce roots to spread out.