Most garden plants form powerful partnerships with mycorrhizal fungi—microscopic allies that extend a plant’s root system, deliver nutrients, improve drought tolerance, and strengthen soil structure. But not all plants participate in these underground alliances. Knowing which crops do and do not form mycorrhizal relationships helps you fine-tune soil care, fertilizer use, and crop rotations for maximum soil health and productivity.

Below is a clear guide to help you garden with the underground network in mind.

Table of Contents

Why Mycorrhizal Relationships Matter

Mycorrhizal fungi attach to plant roots and act as nutrient-gathering extensions, increasing a plant’s access to water and minerals such as phosphorus, zinc, and copper. In exchange, plants feed the fungi carbon-rich sugars released from their roots.

These relationships:

Improve plant health
Reduce fertilizer needs
Increase resilience during heat or drought
Build long-term soil structure

But these benefits only occur when plants that use mycorrhizae are present.

Plants That Form Mycorrhizal Relationships

Most garden plants fall into this group and actively benefit from fungal partnerships.

Vegetables That Form Mycorrhizae

Solanaceae (Nightshades)

Tomatoes
Peppers
Eggplant
Potatoes

Cucurbits

Cucumbers
Squash (summer and winter)
Pumpkins
Melons and watermelons

Legumes

Beans
Peas
(Note: They partner with both rhizobia bacteria and mycorrhizal fungi.)

Alliums

Onions
Garlic
Leeks
Shallots
Scallions

Corn and Grains

Sweet corn
Popcorn
Barley
Wheat

Root Crops

Carrots
Parsnips
Sweet potatoes

Leafy Greens

Lettuce
Swiss chard

Fruit and Nut Trees

These are highly dependent on mycorrhizal fungi.

Apples
Peaches
Plums
Pears
Citrus
Avocado
Almonds
Walnuts

Shrubs, Vines, and Perennials

Many ornamentals are strongly mycorrhizal:

Roses
Grapes
Blueberries (ericoid mycorrhizae)
Raspberries/blackberries
Lavender
Rosemary

**Plants That Do Not Form Mycorrhizal Relationships**

This group is smaller but extremely important. These crops do not form mycorrhizal partnerships at all, and adding inoculants will offer no benefit.

Non-Mycorrhizal Plants (Important for Gardeners)

Brassicas

These vegetables do not form mycorrhizal relationships:

Broccoli
Cauliflower
Cabbage
Kale
Collards
Brussels sprouts
Mustard greens
Arugula
Radishes
Turnips
Kohlrabi

Spinach

All spinach varieties
(Note: Swiss chard is mycorrhizal, but spinach is not.)

Beet Family (Some Members)

Beets
Sugar beets
(Note: Their close relative Swiss chard does form relationships.)

Lambsquarters and Chenopodium Weeds

Garden weeds in this family are also non-mycorrhizal.

Why It Matters for Garden Management

1. Crop rotation

Follow non-mycorrhizal crops with mycorrhizal crops to rebuild fungal networks.
Avoid growing brassicas back-to-back in the same bed if you want a strong fungal presence.

2. Fertilizer use

Non-mycorrhizal plants—like brassicas—often require more available nutrients in the soil because they do not have fungal partners to help them gather minerals.

3. Use of inoculants

Inoculants will only help crops that actually form relationships.
Don’t waste them on brassicas, spinach, or beets.

4. Soil building

Beds grown in brassicas or spinach benefit from:

Cover crops (especially grasses and legumes)
Leaving roots in place
Minimal disturbance
Compost and mulch

These practices help restore fungal networks before planting the next mycorrhizal crop.

Conclusion

Mycorrhizal fungi are silent partners that help most garden plants thrive—but not all plants participate in this underground alliance. By understanding which crops need and benefit from these fungi, you can improve soil health, reduce fertilizer inputs, and strengthen your garden’s long-term productivity.