Leeks are an allium, in the same family as onions and garlic. Like other alliums, leeks have a strong odor. Many plants benefit from being planted near leeks. Other plants benefit from leeks when planted near them. Here are the best companion plants for leeks and the ones not to plant near leeks.
Why Do Leeks Need Companion Plants?
Companion plants can do a number of things for the plants they are near. Here are the specific ways companion plants help leeks.
Nasturtium, carrots, marigolds, rosemary, and thyme repel insects that attack leeks like the onion maggot and leek moths. Chamomile is said to reduce the fungal and bacterial diseases that leeks get.
Bring Pest Predators
Nasturtiums and marigolds attract beneficial insects that attack leek pests. These insects spread to the leeks and eat any pests on them.
Beets and parsnips bring nutrients from far down in the soil and make them available to the leeks. This helps the leeks grow better and faster.
Break Heavy Soil
Parsnips, celery, and beets all break up the soil, making it easier for the leeks to grow and to get the air and nutrients they need.
Improve the Flavor
Carrots, rosemary, chamomile, and thyme are said to improve the flavor of leeks when grown with them.
Benefit from Leeks
Parsnips, peppers, tomatoes, melons, lettuce, strawberries, and Brassicas benefit from being near leeks. Leeks repel the insects from them and help them grow better.
You can read more about companion plants in general in my article, “Companion Planting – Everything You Need to Know.”
Top 15 Best Companion Plants for Leeks
Here are the top fifteen companion plants for leeks and the ways these plants benefit leeks or get benefits from being planted near leeks.
Leeks repel carrot rust flies while carrots repel onion flies and leek moths. Alternate planting leeks and carrots and both crops will grow better. Carrots are also said to improve the flavor of leeks. If you don’t want to alternate carrots and leeks, plant carrots between rows of leeks.
Leeks repel carrot flies that might prey on the parsnips. The parsnips help break up heavy soil and aerate it, so the leeks can grow better. Parsnips, like beets, have a long tap root to bring nutrients and water up from deep in the soil where leeks and other plants can access it. You can alternate parsnips and leeks or plant parsnips in the space between rows of leeks.
Leeks repel aphids, ants, and other pests from peppers. They can be planted in a border around the row the peppers are growing on or interspersed with the pepper plants. Some pepper plants grow large, so make sure the leeks are far enough from the pepper plants to get the sun they need.
Leeks repel pests with their strong smell. Plant them as a border around melons to repel the many pests that eat the melon plants. Don’t try to plant leeks in the melon patch as the melons will grow over them and smother them.
Like peppers, tomatoes benefit from having leeks around. Leeks repel aphids, ants, and other pests from the tomato plants. Again, you can plant the leeks as a border on the row the tomatoes are growing in, or in a circle around the tomato plants. Remember that tomato plants can get quite large, so plant the leeks far enough back that they will not be in the shadow of the tomato plants.
Both leeks and celery are grown in a trench. They both need the same nutrients and the same soil. This makes it handy to grow leeks and celery near each other. Leeks will keep carrot root flies, aphids, and leaf miners away from the celery. Celery and leeks each help break up the soil, making it easier for both of them to grow.
Lettuce and other leafy greens benefit from the strong odor of leeks that repels pests. Leeks can shade lettuce when it gets hot if planted to the west of the lettuce. Plant leeks around lettuce, or plant lettuce in the spaces between rows of leeks. Loose leaf lettuce can be used as a living mulch around the leeks.
Leeks and strawberries grow well together. Strawberries can be used as a living mulch to hold soil moisture and keep down the weeds. Leeks can be planted as a border around the strawberry patch to keep pests away from the strawberries or interspersed in the row with strawberries.
Beets have long tap roots that go down 36-48 inches into the ground. They draw up water and nutrients from deep underground. The excess water and nutrients are available to leeks that are planted near the beets. Beets also help break up the soil so the leeks can grow more easily. In return, the leeks repel pests from the beets. You can plant leeks around beets, interspersed with beets, or plant beets in the rows between leeks.
Brassicas like cabbage, cauliflower, broccoli, Brussel sprouts, kohlrabi, and kale grow well with leeks. All require the same soil moisture. The leeks repel aphids and cabbage worms to protect the Brassicas. Pair your cabbage with beets and leeks and all three will grow better. You can plant the leeks in the same row or around the beets, cabbage, and other Brassicas.
Rosemary deters pests that might attack the leeks. It also enhances the flavor of the leeks. Rosemary also attracts beneficial insects that eat pests on leeks. Plant rosemary, which gets quite large, and circle it with leeks, or plant leeks in the next row over from rosemary.
Thyme also deters leek pests and enhances the flavor of the leeks. Thyme attracts pollinators and other beneficial insects that will benefit the whole garden. Some thyme creeps along the ground and makes a good living mulch for leeks. Other thyme is taller and can’t be used that way but can form a border around the leeks or be planted in the same row as leeks.
Chamomile has several benefits for leeks. It is anti-fungal and anti-bacterial, so protects the leeks from many diseases. Chamomile also improves the flavor of leeks and other alliums. Finally, chamomile attracts beneficial insects that will benefit your whole garden. Plant chamomile around your leeks, within the same row, or in the space between rows of leeks.
Nasturtiums repel insects that bother leeks like the onion fly and leek moth. They attract beneficial insects that eat pests and will spread to nearby plants like leeks. Nasturtiums also act as a low-growing, living mulch when planted around leeks. They stabilize soil moisture and keep weeds out of your leek patch. Plant nasturtiums as a border around leek rows or alternating with leeks within a row. You can also plant nasturtiums between rows of leeks.
Like nasturtiums, marigolds repel insects that bother leeks. Beneficial insects love marigolds and will spread out from them to eat pests and pollinate plants. Densely planting marigolds act to keep weeds out of the area they grow, too. Plant marigolds as a border or between rows of leeks.
Top 4 Worst Companion Plants for Leeks
Some plants do not do well with leeks. Here are the four worst plants to put near leeks.
Beans and leeks produce biochemicals that inhibit each other from growing. Don’t plant beans within about six feed of leeks or neither will grow.
Peas are another legume that does not grow well near leeks. Like beans, peas, and leeks produce chemicals that inhibit the growth of each other. Keep peas at least six feet from leeks to keep from having problems.
Black Walnut Trees
Black walnut trees produce a potent chemical that kills almost every plant around them. This chemical is so potent that it stays in the soil for years and years. Do not plant leeks within the drip line of a black walnut tree or where a black walnut tree has been. Everywhere the roots have grown will have the toxic chemical in the soil.
Fennel also produces a chemical that kills any plant put near it. Grow fennel away from other plants. It doesn’t act as a companion plant for anyone.
In conclusion, leeks repel pests off of many of their companion plants such as lettuce, peppers, tomatoes, and melons. Some companion plants repel the insects that plague leeks, such as onion maggots and leek moths, away from the leeks. Other companion plants, like marigolds and nasturtiums, bring pest predators to the leeks. Root crops such as beets and parsnips planted near leeks help break up heavy soils and bring nutrients to the surface that leeks can use. Finally, a few companion plants, like rosemary and thyme, improve the taste of leeks. The best plants to put near leeks are carrots, parsnips, peppers, melons, tomatoes, celery, lettuce, strawberries, beets, Brassicas, rosemary, thyme, chamomile, nasturtiums, and marigolds. Plants to keep away from leeks include beans, peas, black walnut trees, and fennel.