You spent a fortune on bagged hardwood mulch last year. It looked good for about 4 weeks, then weeds came up through it, your hose still ran daily, and the bag price went up again for spring. There is a better mulch, it works dramatically better in nearly every measure, and it is free. Arborist wood chips, the mixed pile of bark, sapwood, and leafy material that comes out of every tree care truck in your neighbourhood, are the highest-performing organic mulch ever tested in university trials. Most arborists are happy to drop a truckload at your driveway for free because it saves them the tip fee.
Here's the short version: call your local tree service or sign up for ChipDrop. Apply a 3 to 4 inch (7.5 to 10 cm) layer over your soil, keeping it 2 to 3 inches (5 to 7.5 cm) away from tree trunks and plant stems. Top up once a year. Watch your soil get better and your weeds disappear while your hose stays in the shed.
Quick answer
Arborist wood chips outperform every other organic mulch in published university trials. Apply them 3 to 4 inches deep on top of soil (never mixed in), keep a 2 to 3 inch gap around stems and trunks (the no mulch volcano rule), and top up annually. Best free source: ChipDrop or your local tree care company. The nitrogen tie-up rumour is overstated for surface application, the science from Linda Chalker-Scott at WSU is clear on this.
Arborist wood chips are not the same product as the bagged "hardwood mulch" at the garden centre. The bagged version is usually shredded bark only, dyed brown or black, milled to a uniform texture. Arborist chips are the raw output of a tree crew's chipper: a mix of bark, sapwood, fresh wood, twigs, and green leaves all together. That mix matters. The variety of particle sizes and the inclusion of leafy material makes it the best-performing landscape mulch in the Washington State University Extension home garden trials conducted by Dr. Linda Chalker-Scott over more than 15 years.
Why this works (the permaculture angle)
A forest does not buy mulch. The trees drop leaves, branches, and bark, and the system breaks them down into humus over years. Arborist wood chips replicate that process at speed. The mixed particle sizes feed both bacteria and fungi at the same time, build long-lived soil carbon, and create the same conditions a healthy woodland floor would. The free part is not a coincidence either; permaculture is about closing loops, and there is a loop already running between every tree crew and every gardener who wants free organic matter.
| Benefit | Documented effect |
| Soil moisture retention | 40 to 50 percent less evaporation compared with bare soil (WSU trials) |
| Weed suppression | Greater than 90 percent reduction in annual weed germination at 3 to 4 inch depth |
| Soil temperature | Buffers the upper 4 to 6 inches (10 to 15 cm) by 8 to 12 F (4 to 7 C) versus bare soil |
| Mycorrhizal fungi | Significant increases in fungal colonization vs. uncovered soil |
| Earthworm populations | Documented increases beneath wood chip mulches versus bare soil controls |
| Soil organic matter | Measurable build-up over 3+ years of continuous use |
Sources: WSU Extension, Using Arborist Wood Chips as a Landscape Mulch; Chalker-Scott, Mulches: The Good, the Bad, and the Ugly (PDF).
The most persistent piece of bad advice in home gardening is that wood chips lock up nitrogen and starve plants. It is a half-truth that has become a full myth. Here's what's actually true: when you mix fresh wood chips into the soil, the decomposing bacteria pull nitrogen from the surrounding soil to break down the carbon, temporarily reducing what is available to plants. When you leave the wood chips on the surface (the only correct way to use them), the nitrogen reaction happens only at the very thin soil-mulch interface in the top inch or two, far above where established plant roots are working. Chalker-Scott's research shows no measurable nitrogen deficiency in established gardens mulched with wood chips on the surface, and multiple field observations back this up.
The exception worth knowing: brand new seedlings planted directly into fresh wood chips can struggle in their first weeks. Solution: keep the wood chip layer pulled back from new seedling planting holes and apply a thin compost layer where seeds will germinate. Our composting starter guide covers building that compost supply.
ChipDrop is the easiest US route. You sign up online, drop a pin on a map, set how big a load you can handle (a small dump is roughly 4 to 6 cubic yards, a full truck can be 20+), and wait. When an arborist working nearby has a load to dispose of, they call ChipDrop and you get a notification. Loads typically arrive within 2 to 8 weeks. Optional $20 to $80 priority fee speeds up delivery and lets you specify size preferences.
Call local tree care companies directly. A simple phone or web search for "tree service near me" plus a quick call: "Do you have free wood chips you need to dispose of? I have space at my driveway and can take a load whenever you have one." Most will say yes within a week. They save the dump fee, you get the chips.
Municipal sources. Many city tree crews and parks departments stockpile chipped material and offer it free to residents. Worth a call to your local public works.
Clear weeds first if heavy
Wood chips suppress new weed germination but do not kill established perennial weeds well. Pull or smother thick weed cover with cardboard before mulching. Sheet mulching beneath wood chips is the cleanest start.
Apply 3 to 4 inches deep
Less than 2 inches will not suppress weeds reliably. More than 5 inches can hold too much moisture against stems. The sweet spot is 3 to 4 inches (7.5 to 10 cm) measured after settling, not when freshly piled.
Keep mulch off trunks and stems (no volcanoes)
The single most damaging mulch mistake is piling wood chips up against tree trunks. The Illinois and Ohio State Extensions document mulch volcano damage including bark rot, vascular strangulation, rodent feeding, and tree decline. Maintain a 2 to 3 inch (5 to 7.5 cm) bare ring around each trunk.
Top up once a year
Wood chips decompose into soil over 1 to 3 years. An annual 1 to 2 inch (2.5 to 5 cm) refresh in spring or autumn maintains the working depth.
Where to be cautious
Avoid wood chips from black walnut (juglone risk) unless aged 6+ months. Skip dyed or treated wood chips entirely on edible-garden soil; the dyes and binders are not food-safe. Wood chips work brilliantly under fruit trees, around perennials and shrubs, and on garden paths, but use only well-aged chips (6+ months) directly in vegetable beds where you plant annual seedlings, to avoid temporary nitrogen interference at the seedling root zone.
Wood chips are the structural layer beneath a healthy food forest in year 1, the medium-term feed for the soil microbiome, and the gradual builder of humus that turns subsoil into topsoil. Pair with living ground covers once they establish (year 2 to 3), at which point you can stop applying fresh chips and let the plant layer take over.
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Subscribe freeDo fresh wood chips hurt plants?
Surface-applied fresh wood chips do not hurt established plants. They are safe around trees, shrubs, and perennial beds. They can temporarily slow new seedlings planted directly into them because of the soil-mulch interface nitrogen reaction. Solution: pull mulch back where you plant seeds, apply compost in the planting holes, mulch returns to position after seedlings establish.
Why do some people say not to use wood chips as mulch?
Most "do not use wood chips" advice is based on the nitrogen tie-up myth or on incorrect application (volcanoes, mixing into soil, using on annual seed beds). Linda Chalker-Scott's WSU research has spent over a decade addressing these concerns directly, and the documented benefits substantially outweigh the limited cautions.
Where can I buy wood chip mulch?
You probably should not need to buy it. Free sources include ChipDrop, local tree care companies, and municipal tree crews. If you must buy, look for "bulk arborist chips" from a local landscape supplier; expect $20 to $40 per cubic yard. Avoid bagged dyed bark for edible gardens.
What kind of wood chips are bad for gardens?
Avoid dyed or treated wood chips on edible soil. Be cautious with black walnut (juglone, age 6+ months before using on sensitive plants). Skip any chips from pressure-treated lumber, painted wood, or pallets of unknown origin. Mixed arborist chips from healthy trees in your area are the gold standard.
Does fresh mulch hurt plants in pots and containers?
Yes, more so than in-ground. Containers have limited soil volume, so the surface-area-to-soil ratio is much higher, and the nitrogen reaction at the soil-mulch interface affects a larger proportion of the root zone. Use only finished compost or fully aged wood chip mulch in containers, never fresh.
How long do wood chips last as mulch?
Hardwood chips: 2 to 3 years before significant decomposition. Softwood (pine, fir): 12 to 18 months. Mixed arborist chips with green leaves: 12 to 18 months. Plan to top up annually with a fresh 1 to 2 inch (2.5 to 5 cm) refresh layer.