What can I plant with leeks?

QUESTION: I’m trying to plan my garden and want to try growing leeks. What can I plant with leeks? -Jennifer T.

ANSWER: Many gardeners turn to companion planting to set their gardens up so that space is maximized and plants support one another through their natural symbiotic relationships. Growing next to each other, some plants can improve others’ taste, some may repel the pests that would otherwise plague their neighbors, and some grow tall to offer protective shade to smaller plants.

Sometimes, companion planting means pairing up plants that won’t compete too harshly for resources, either because they thrive on different nutrients or because their roots access the soil at different levels of depth. Many insects that are garden pests are repelled by the scent of leeks, making it an excellent companion plant for many vegetables. However, other plants can benefit the leek in return when they’re planted close together. The plants we’ve listed below are recommended companions for leeks.

• Apples: In addition to fending off borers, slugs, and mites, leek plants will also prevent apple scab and similar fungal diseases. Plant the leeks within a few feet of the base of the trees.

• Alliums: All members of the allium family we grow in the vegetable garden (garlic, onions, shallots, and leeks) have very similar preferences for their environment and ongoing care, which makes them perfectly suited to grow alongside one another. However, they also share insect pests, so keep your allium patch small to avoid drawing in the insects that can plague alliums. Several small allium patches sprinkled throughout the garden are better than one large one.

• Beets: Beets and leeks share similar care preferences, and are known to do especially well with cabbage added into the mix to triple up on companions and make the most of your garden space.

• Cabbage: Cabbage and leeks have similar needs, and many gardeners recommend growing beets with these two for a triple companion planting to save on space. Leeks will repel the cabbage white caterpillars and whiteflies that plague cabbage plants, too.

• Calendula

• Carrots: Leeks and carrots have a truly mutually beneficial relationship—the leeks protect the carrots from carrot flies, while the carrots protect the leeks from leek moths and onion flies. The two root crops also help loosen the soil for one another as they grow, so the underground leek bulbs and carrot roots can grow larger more easily. Put the leeks (or leeks and other alliums) on either side of your carrot patch to flank the carrots and keep invaders at bay.

• Celery: Both celery and leek plants perform well when they’re trenched, which makes it easy to grow the two together. Because celery is bushy and leek grows fairly vertically, you can squeeze the two plants together and intersperse them in a garden plot. Both plants love potash (potassium), so you can treat the area where they’re growing with a high-potassium fertilizer and save both space and fertilizer when they grow next to one another. The leeks will also defend the celery plants by repelling the carrot root flies, aphids, and celery leaf miners that can otherwise cause trouble.

• Fruit trees: Some leek plants growing nearby are of major benefit to fruit trees because the leeks (like all allium plants) will deter borers, slugs, and mites that the trees might otherwise struggle with. Make sure to plant your leeks within a few feet of the bases of the fruit trees you wish to protect.

• Lettuce: The strong scent of the leeks will deter pests from the lettuce plants, and the leeks can also offer the tender lettuce some much-needed shade when the weather gets hot.

• Nasturtium

• Parsley

• Parsnips: The aroma of leeks will deter the carrot root fly  that parsnip plants often struggle against.

• Poppies

• Strawberries: The strong scent of the leeks fights off many of the pests that would otherwise plague strawberry plants.

• Tomatoes: The aroma of leeks growing nearby will stave off many of the pests that would normally cause problems for tomato plants in the garden, especially those troublesome aphids.