Strong soil makes strong fruit trees, and soil-building plants are the secret to getting there. These living fertilizers don’t just look pretty—they work behind the scenes to enrich the soil, loosen tough ground, and add nutrients your trees can actually use. Learn how the right soil-building plants can turn your fruit garden into a healthier, more resilient ecosystem.
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Companion planting isn’t about a single quick fix or adding one magic plant. It’s about creating a diverse ecosystem of plants, wildlife, and microorganisms that support each other and strengthen the whole garden. Over the years, I’ve seen my fruit trees grow healthier and more productive as I’ve added different companions—but the biggest change came when I started including plants that improve the soil.
Soil is the heart of gardening. It’s what determines a plant’s health, productivity, and lifespan. And the foundation of every thriving fruit tree is rich, living soil—something companion plants can help you build naturally.
> This is Part 4 in a series of 6 articles about fruit tree companion planting. For complete information about this topic, I recommend starting at the beginning,
Why Soil-Builders Matter for Fruit Trees
Fruit tree roots rely on the soil’s ability to hold water and deliver nutrients. Because fruit trees are heavy feeders that remain in place for decades, they continually draw nutrients out of the ground. Without replenishment, the soil becomes depleted. A healthy soil microbiome helps by breaking down organic matter into nutrients that trees can actually absorb.
Soil-building companion plants act as “living fertilizer,” but their benefits go even further. Studies show that companion planting increases the diversity of soil microbes compared to monoculture (source). The more these plants improve the soil for you, the less effort you’ll need to put in as a gardener.
NOTE: Companion planting blends agriculture, ecology, and gardening lore, but much of the advice online is recycled with little evidence. My suggestions are based on research (linked where relevant), as well as experiments & observations in my own garden, with a focus on the whole environment rather than individual plants. Companion planting works best alongside integrated pest management, organic sprays & fertilizers, and other cultural practices.
Companion Plants Can Help the Soil By:
- Fixing nitrogen. Nitrogen-fixing plants have a symbiotic relationship with a certain kind of bacteria, which pulls nitrogen from the air and converts it to a form that can be absorbed by plants.
- Accumulating nutrients. Dynamic accumulators pull nutrients from deep down and cycle them back to the surface.
- Improving soil structure. Plants with deep tap roots break up compacted, heavy soils.
- Feeding soil biology. The more diverse plant species in an area, the more worms, microbes, bacteria, and fungi that support tree roots.
Curious about any garden-related terms? Click on a highlighted word in the text, or visit The Fruit Grove Glossary to find out more.
How to Choose the Right Soil-Building Plants
Most of these companion plants will work well with just about any fruit tree. A key consideration is climate - for example, I know plants in my Texas garden need to be able to survive periods of extreme heat, drought stress, as well as other periods of humidity and excessive rainfall. Here are a few other considerations when choosing soil-building companions:
Nitrogen Fixers vs. Dynamic Accumulators
What nutrients do your fruit trees need most? All fruit trees benefit from a steady source of nitrogen, which makes nitrogen-fixing plants essential companions. Legumes like soybeans, fava beans, cowpeas, vetch, red clover, alfalfa, and lupines are excellent options. To get the most benefit, these plants need to be cut down and incorporated into the soil as they decompose. Most of the nitrogen is stored in the plant itself, though some does release into the surrounding soil while the plant is alive (source).
Dynamic accumulators—such as comfrey, amaranth, daikon, and many others—draw up nutrients from the soil and store them in their tissues. Until recently (2021), research on this idea was limited, but now a database has been developed that documents which plants accumulate which nutrients.
There are a few caveats to keep in mind. The healthier your soil, the more nutrients these plants can absorb. And just like nitrogen fixers, the greatest benefit comes when the plant dies back or is cut down and its tissues decompose into the soil. Use these types of plants as chop-and-drop mulch, meaning that once they have grown full size, cut them back and spread the "green manure" around to act as a mulch that can decompose in place.
Root Depth
Fruit trees thrive in well-draining soil that’s rich in organic matter. Deep-rooted plants—like comfrey, carrots, or watermelon—can help break up heavy, compacted soil while pulling nutrients from deeper layers. Just be sure not to plant them too close to your fruit trees, since their roots can compete for space and resources.
Growth Habit
Do you want a spreading groundcover like alpine strawberries, creeping thyme, clover, or squash vines? Or is space an issue and you need a clump-forming plant, such as basil, chives, or comfrey?
Light Requirements
Remember that these plants will be growing near, or even under, fruit trees. Most fruit trees need 6-8 hours of full sun per day, but the tree's canopy will cast dappled shade. Situate plants that need full sun outside of the canopy, and let shade-loving plants grow under the tree.
My Favorite Soil-Building Companions for Fruit Trees
As mentioned earlier, there are hundreds of fruit tree companion plants that improve soil in different ways. I’m always experimenting with new varieties and combinations, but these are some of my favorite tried-and-true soil builders that I grow around my own fruit trees.
Comfrey
Often called the “king” of companion plants, comfrey is a fast-growing dynamic accumulator with deep roots that break up compacted soil. Its wide, sprawling leaves act as a living mulch, shading and protecting the soil. While common English comfrey has a reputation as a dynamic accumulator of various nutrients, recent studies show that it may not work as well as gardening lore would suggest (read more about this here). For example, it is not an accumulator of nitrogen, but it is for cobalt and iron.
Even with its somewhat diminished reputation, I (and many successful gardeners) still grow comfrey as a companion plant and source of green compost. Most comfrey varieties spread aggressively, but the sterile variety 'Bocking 14' stays in a neat mound. I grow 'Bocking 14' around my peach trees and near my compost bin so I can easily “chop and drop” the foliage throughout the season.
Peanuts
Peanuts - my new favorite companion plant - combine deep roots that loosen soil with the nitrogen-fixing power of legumes. I grow ‘Wynne’ and ‘Bailey II Virginia’ just outside the canopy of my peach and apple trees to avoid root competition. After harvesting the peanuts and letting them dry, I trim the tops and leave them in place as mulch where they decompose and release nitrogen back into the soil. As a bonus, peanuts are heat- and drought-tolerant, thriving even in poor soil.
Borage
Also known as starflower, borage accumulates potassium and magnesium while serving as an excellent green mulch when the plants die back. Its flowers are striking and attract plenty of pollinators. Borage reseeds easily: I typically plant in spring, let the plants die in place, and enjoy a second bloom in fall, with the cycle continuing year after year.
Amaranth
A fantastic chop-and-drop plant, amaranth accumulates potassium, phosphorus, calcium, magnesium, and iron. Its deep, sturdy roots also help break up compacted soil. With many varieties to choose from, my favorites are the deep red 'Love Lies Bleeding' and the golden-bronze 'Golden Giant'. I grow amaranth both in my kitchen garden and along the borders of my small backyard orchard.
White, Red, or Crimson Clover
Clover is one of the best nitrogen-fixing legumes and is often used as a cover crop. When tilled into the soil, it breaks down and enriches the ground with nitrogen. Clover does spread quickly, but if you have the space, it makes a great living ground cover around fruit trees.
A Note About Cover Crops
Cover cropping is the practice of planting beneficial crops after the primary crop has been harvested. This concept is often used in orchards to fill in the space between trees. Cover cropping is another type of companion planting, where plants are chosen to provide benefits to the soil and surrounding plants.
In the case of fruit trees, cover crops are planted to protect and improve the soil while reducing weed competition. Some common orchard cover crops are oats, clover, hairy vetch, fescue, rye, and alfalfa. Once the plants reach maturity, they can be mowed or crimped to die in place and break down, improving the soil.
The above cover crops typically spread easily over a large area, so they aren't very well suited to a suburban backyard. But you can have similar effects in your smaller backyard garden by strategically choosing plants (like the ones mentioned in this article!) with the same soil protecting/enhancing benefits.
Next Step: Weed Suppressors & Living Mulches
Now that your soil is thriving, the next step is protecting it—keeping weeds at bay and moisture in. In the next article, we’ll look at the best groundcovers and living mulches to plant under fruit trees, and which ones I’ve learned to avoid.
> Read Part 5: The Best Living Mulches & Groundcovers for Fruit Trees
- Part 1: Fruit Tree Companion Planting (Overview)
- Part 2: Pollinator Plants
- Part 3: Pest Control Plants
- Part 4: Soil Building Plants
- Part 5: Living Mulch
- Part 6: Designing a Companion Plan
