What to Plant with Fennel: A Complete Guide

Fennel is an aromatic and distinctively flavored herb that can add complexity to many dishes. But when it comes to your garden fennel can be a bit finicky about its companion plants. Understanding what to plant with fennel is key to a successful harvest.

With its feathery, herbaceous foliage and anise-like flavor, fennel is a unique plant. There are two main types of fennel:

• Herb fennel – Grown for its edible leaves and seeds, It has limited bulb development

• Florence fennel – Cultivated for its swollen bulb-like base in addition to its leaves and seeds. The bulb has a more mellow, subtle flavor than the herb type.

Both types of fennel grow as upright, branching plants reaching around 4-5 feet tall at maturity. They produce clusters of small yellow flowers beloved by beneficial insects.

Fennel thrives in fertile, well-drained soil and full sun. It is a heavy feeder that requires sufficient nutrients and moisture for optimal growth. Proper spacing between plants is also important to avoid crowding.

The Best Companion Plants for Fennel

When interplanting fennel, choose companion plants carefully. Here are some of the best:

• Dill – Dill attracts beneficial insects like ladybugs while repelling aphids and other pests. It complements fennel nicely in scent and appearance.

• Coriander – The flowers of coriander, also known as cilantro, attract hoverflies and parasitic wasps to control aphids. It’s a great culinary pairing as well.

• Anise – In the same plant family as fennel, anise has a harmonious look and scent. The two herbs make good garden partners.

• Marigolds – Marigolds deter nematodes, aphids, and other garden pests with their pungent odor. Their bright blooms also attract pollinators.

• Nasturtiums – With their trailing habit, nasturtiums suppress weeds around fennel. Their flowers add a pop of color while also bringing in beneficial insects.

Companion Plants to Avoid with Fennel

Due to its allelopathic tendencies and ambitious growth, fennel does not always mingle well with other plants, especially:

• Nightshades – Tomatoes, peppers, eggplants and other nightshades are sensitive to the compounds exuded by fennel roots. Keep them far apart.

• Legumes – Beans and peas grow poorly near fennel and may have reduced yields.

• Root vegetables – Onions, garlic and carrots may compete with fennel for nutrients and not thrive as companions.

• Other herbs – Basil, parsley, and rosemary growth can be stunted by the presence of fennel. They are best planted separately.

Tips for Successful Fennel Companion Planting

• Give fennel plenty of space – at least 12 inches between plants. This prevents crowding and competition.

• Use raised beds or containers to isolate fennel if space is limited. Its long taproot necessitates deep soil.

• Plant fennel downwind of more sensitive companion plants to reduce allelopathic effects.

• Add compost and organic fertilizer to replenish nutrients being used by fennel. Side dress plants during the growing season.

• Mulch around fennel to retain soil moisture and reduce weeds. Be sure not to cover the bulb.

• Stagger plantings over several weeks to ensure a continuous fennel harvest. Successive sowing prevents bolting.

An Ideal Fennel Garden Plan

Here is one example of an ideal garden plan showcasing fennel and its best companion plants:

• Plant fennel in the center of a raised bed, surrounded by marigolds and nasturtiums.

• Interplant dill around the outer edges. Include some coriander as well for diversity.

• Fill separate garden beds with nightshades, root crops, legumes and any herbs that could be inhibited by fennel.

• Use trellises and vertical space to cultivate vining plants like cucumbers above and around the fennel so they are not impacted by fennel’s roots.

With the right companion plant choices, fennel can be a great addition to any herb or vegetable garden. Paying attention to pairing both above and below ground will lead to success for fennel and its companions alike.