To mulch around trees, spread 2 to 4 inches of wood chips, shredded bark or leaves in a wide, flat ring. Keep it 3 to 5 inches off a young trunk so the root flare shows. Make the ring about 2 feet across for a seedling and 3 feet for a sapling. Never build a volcano.
This is the potting shed of TN Nursery, the third-generation family nursery in Altamont, Tennessee, growing native trees and plants since 1959. This project shows how to mulch around trees and shrubs, from a seedling row to an older tree. Most of our plants arrive bare-root and dormant, and mulch is the last step of planting them. You will find ring sizes and bag counts for the plant sizes we ship.
How to mulch around trees: what you need
- Organic mulch: wood chips, shredded hardwood bark, pine needles or shredded leaves
- A flat spade or half-moon edger to cut out grass
- A garden rake and a hand trowel
- A tape measure or a stick cut to the ring's radius
- A hose or watering can
Mulching a tree or shrub, step by step
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Plant and water in first
Set your bare-root tree at the depth it grew in the nursery and firm the soil. Water it well so the soil settles around the roots. Mulch goes on after this soaking, never before.
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Clear the grass from the ring
Mark the ring's width with your stick or tape. Cut out the grass and weeds inside it with a spade. Grass competes with young roots for water, so the cleared ring matters as much as the mulch.
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Find the root flare
The root flare is where the trunk widens just before it meets the roots. On a small sapling it may be only a slight bulge at soil level. This spot must stay uncovered.
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Spread the mulch flat
Tip the mulch into the ring and rake it level, 2 to 4 inches deep. Keep it flat, like a pancake, not mounded.
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Pull it back from the trunk
Use your hand or a trowel to pull mulch away from the stem. Leave a bare gap of 3 to 5 inches on a young tree, and more on a mature one. The ring now looks like a donut, with the trunk in the hole.
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Water the mulch and tidy the edge
Water the ring so the mulch settles and stays put. Rake any strays back inside the edge. Cut the grass edge again whenever it creeps in.
How deep should mulch be around trees?
Around trees and shrubs, 2 to 4 inches of mulch is enough, and no more. Deeper mulch starves the roots of air. Penn State Extension advises a thinner layer in two cases: fine mulch, and soil that drains poorly.
| Situation | Mulch depth | Gap at the trunk |
|---|---|---|
| Coarse wood chips or bark | 3 to 4 inches | About 3 to 5 inches on young trees |
| Fine mulch, such as compost or finely shredded material | 1 to 2 inches | About 3 to 5 inches on young trees |
| Wet, poorly drained soil | Less than 2 inches | About 3 to 5 inches on young trees |
| Mature, established tree | 2 to 4 inches | About 8 to 10 inches |
The depths and gaps above follow Penn State Extension and The Morton Arboretum. Measure by pushing a finger or a ruler straight down to the soil.
How wide to make the ring, and how many bags you need
Wider is better than deeper. The Morton Arboretum suggests mulching out to the drip line on young trees. The drip line is the edge of the outermost branches. A young sapling's branches are short, so as a rule of thumb, make the ring a bit wider to keep grass well back.
- Seedlings under 2 feet, like our pawpaw tree seedlings or black locust seedlings: a ring about 2 feet across.
- Saplings 1 to 2 feet tall, like a 1–2 foot pawpaw tree or Eastern redbud tree: a ring about 3 feet across.
- Saplings 3 to 4 feet tall: a ring about 4 feet across.
- Shrubs such as witch hazel or red osier dogwood: a good rule of thumb is a ring a little past the branch tips. Mulch a group of shrubs as one bed.
- Older trees: at least 4 to 5 feet across, as The Morton Arboretum advises, and out to the drip line where you can.
To count bags, do some quick math. A common 2-cubic-foot bag covers about 8 square feet at 3 inches deep, or about 12 square feet at 2 inches.
| Plant size | Ring width | Area | 2 cu ft bags at 3 inches deep |
|---|---|---|---|
| Seedling under 2 feet | 2 feet | About 3 sq ft | Under half a bag |
| Sapling 1 to 2 feet | 3 feet | About 7 sq ft | About 1 bag |
| Sapling 3 to 4 feet | 4 feet | About 13 sq ft | About 1½ bags |
| Older tree, smallest ring | 5 feet | About 20 sq ft | About 2½ bags |
| Older tree, wider ring | 6 feet | About 28 sq ft | About 3½ bags |
Mulch volcanoes: why they harm trees and how to fix one
A mulch volcano is a tall cone of mulch piled against the trunk. It looks tidy, but it hurts the tree. Penn State Extension lists what too much mulch can cause:
- Roots short of oxygen
- Damage to the inner bark, the living layer under the bark
- Fungal and bacterial disease
- Insects such as carpenter ants and termites moving in
- Voles and mice chewing the bark under cover
- Heat from rotting mulch
To fix a volcano, dig gently near the trunk with a hand trowel until you find the root flare. Then rake the extra mulch outward, level, to the edge of the ring. Keep it 2 to 4 inches deep and leave the flare bare. Penn State Extension's mulching guide describes the same fix.
Watch out: Do not pile fresh mulch on top of old mulch each year. Stacked layers turn a good ring into a volcano within a few seasons.
Best mulch for trees and shrubs
Organic mulch is best because it breaks down and feeds the soil. These all work well around trees and shrubs:
- Hardwood bark and wood chips. Penn State Extension calls hardwood bark very good, low-cost mulch, especially a blend of bark, wood and leaves.
- Shredded leaves. Free each fall, and the natural mulch of a woodland.
- Pine needles. The Morton Arboretum notes they do not make the soil acid.
- Compost, blended with a coarser mulch.
Some mulches need care. The Morton Arboretum warns that cocoa bean shells are toxic to dogs. Sawdust packs down, and sawdust from treated lumber should not be used. Mushroom compost varies in quality, so use it sparingly.
When to mulch and when to top it up
For bare-root trees, mulch on the day you plant, right after you water in. The ring keeps the soil moist while new roots grow.
- New bare-root plantings: mulch on planting day, whatever the season.
- Existing beds in spring: Penn State Extension names mid-spring as the best time, once the soil has warmed.
- Existing beds in fall: The Morton Arboretum says to wait until the soil has cooled and frosts are regular, not after just one frost.
- Every year: check the depth with a finger before adding any. Top up only to bring it back to 2 to 4 inches.
- Matted mulch: break it up with a hand rake to freshen it, rather than adding more.
- After each top-up: pull mulch back from the trunk again.
Mulching questions
Are you supposed to mulch around trees?
Yes. A flat ring of mulch holds moisture in the soil, keeps grass from competing with young roots, and evens out soil temperature. It also keeps mowers and string trimmers away from the trunk. Young, newly planted trees gain the most, so mulch bare-root trees on the day you plant them.
How many bags of mulch do you need to go around a tree?
It depends on the ring's width and depth. A common 2-cubic-foot bag covers about 8 square feet at 3 inches deep. So a 3-foot ring takes about one bag, a 4-foot ring about one and a half, and a 6-foot ring about three and a half bags.
Can you put too much mulch around a tree?
Yes. A layer deeper than about 4 inches, or mulch piled against the trunk, can starve the roots of air. Penn State Extension also links too much mulch to bark damage, disease, insects such as carpenter ants, and voles or mice chewing the bark. Keep it flat and level.
What is a common mulching mistake to avoid?
The mulch volcano, a tall cone of mulch piled up against the trunk. A close second is adding fresh mulch on top of old mulch every year until it is far too deep. Keep the root flare bare, the layer 2 to 4 inches deep, and check before you top up.
Can I just lay mulch over dirt?
Yes, spreading mulch over bare soil is fine and is the usual way to do it. Clear grass and weeds out of the ring first, since they compete with young roots for water. Then spread the mulch straight onto the soil, level, and pull it back from the trunk.
