September 7, 2026

Using Fire to Reclaim Pastureland from Cedar and Brush Encroachment

How prescribed fire controls eastern redcedar and brush on pasture: the height thresholds where fire stops working, how much fine fuel you actually need, why grazing deferment comes first, and what a realistic burn interval looks like.

Nobody plants eastern redcedar in a pasture. It arrives on its own — birds drop seed from a fencerow windbreak, a few seedlings hide down in the grass where you'd never notice them from a truck window, and for the better part of a decade nothing appears to be happening. Then one spring you look across a quarter section and realize you're looking at trees.

That slow start is the whole problem. By the time cedar encroachment is obvious enough to worry about, the cheap window for fixing it has usually closed. Fire is the tool that works in that early window, and it's the tool that becomes expensive and difficult once the window passes.

Quick answer:

Fire works on small trees, and only on small trees. Prescribed fire is highly effective on redcedar under a few feet tall and loses effectiveness fast as height increases. Above roughly 10 feet, cutting becomes the practical option.
Fine fuel is the whole ballgame. You need dead grass to carry the fire. NRCS guidance points to roughly 4,000–5,000 lbs of biomass per acre, which usually means deferring grazing on that pasture for a year or two beforehand.
Redcedar doesn't resprout. Kill the top and the tree is dead — unlike mesquite, oak brush, and other sprouting species that need repeat fire.
One burn isn't a fix. NRCS South Dakota suggests a five-to-ten-year interval, and warns that letting it go past about eight years lets regrowth get exponential.
The cost of waiting is real. UNL Extension puts the forage loss from full conversion to cedar woodland at about 75%, with the steepest economic decline hitting between years 15 and 30 of an invasion.

Why cedar takes a pasture so quietly

Eastern redcedar spread is a direct consequence of fire suppression. eXtension's prescribed fire program frames it plainly: as fire dropped out of the landscape after European settlement, prairie and shrubland shifted toward closed-canopy woodland, and in many places toward outright redcedar monoculture. Redcedar is fire-intolerant. In a system that burned regularly, it never got a foothold. In a system that doesn't burn, nothing stops it.

The economics of that shift are worth understanding before you decide whether a burn is worth the trouble. UNL Extension's EC1784 traces the full arc in southeast Nebraska tallgrass prairie: roughly 40 years from open grassland to closed-canopy cedar woodland, with a consistent 75% decrease in forage production once conversion is complete. But the number that should get a rancher's attention is the middle of that curve. Forage loss stays low for the first 15 years — which is exactly why nobody acts — and then between years 15 and 30, cedar displaces herbaceous forage fast enough to be associated with an 80% reduction in potential livestock returns.

USDA NRCS in South Dakota puts the working range at a 30 to 75 percent loss of grazing capacity for encroached pasture, and notes the knock-on effects: displaced grassland birds and upland game, more erosion, degraded soil health as fibrous-rooted grasses get pushed out, and a serious wildfire hazard, because a pasture full of cedar is a pasture full of highly flammable fuel. Their rangeland specialists describe the invasion moving north out of the southern plains "like a green glacier."

The height threshold that decides everything

This is the single most useful thing to know before planning a burn: fire kills small cedars reliably and large cedars poorly.

UNL CropWatch organizes control options straight by tree height. Up to 2 feet tall, burning works — along with cutting, mowing, goats, and broadcast herbicide. From 2 to 10 feet, cutting and individual-tree herbicide treatment become the effective options. Over 10 feet, cutting is simply the most economical treatment left.

That doesn't mean fire is useless on bigger trees, but it changes what kind of fire you need. EC1784 explains the mechanism: high-intensity prescribed fire can kill cedar of essentially any size, but most prescribed burns as actually conducted are low-intensity, and low-intensity fire only kills small to midsize trees. OSU Extension's NREM-2876 draws the same line differently — between ecosystem maintenance (frequent, cheap, low-intensity fire that keeps cedar out) and ecosystem restoration (intensive, high-cost, higher-intensity work to convert a stand back). Their caution is worth quoting in spirit: the high-intensity fire needed for restoration carries greater risk and costs more than the low-intensity fire used for maintenance.

So the honest framing is this. If your cedars are knee-high, fire is cheap and you should be burning. If your cedars are head-high, fire is part of a plan that also includes a saw.

Fine fuel comes before flame

You cannot burn cedar without grass. OSU is blunt about it: none of the control options work without proper grazing management, because the plant community can't recover without a proper stocking rate and periodic fire, and fire can't be used without adequate fine fuel — meaning last year's dead grass.

NRCS South Dakota gives the practical numbers. Ranchers typically defer grazing on the target pasture for one to two years before a burn, growing the ignition and ladder fuels the fire will need, with an optimum of roughly 4,000 to 5,000 pounds of biomass per acre. Texas A&M AgriLife's prescribed burn handbook says the same thing from the planning side: you must plan your grazing management to get the fine fuel density your objective requires, you may have to pull animals off entirely, and planning a year in advance is not unusual.

This is where a lot of first attempts fail. A continuously grazed pasture doesn't accumulate enough continuous fine fuel, the fire creeps and goes out in patches, and the cedars scorch instead of dying. Deferment isn't a formality — it's the input that determines whether the burn does anything at all.

There's a second benefit to deferment that's easy to overlook: it lets your desirable forage plants build vigor and set seed before the fire, so the pasture comes back stronger.

Working with big trees you can't burn out

If you already have cedars over eight feet, you're in restoration territory, and there are two established patterns for combining tools.

The first is cut and stuff. NRCS describes clipping some of the tall cedars mechanically and placing the cuttings at the bases of the larger remaining trees, creating ladder fuel so the fire can climb into crowns it otherwise couldn't reach. EC1784 notes that cost-share dollars for mechanical treatment are increasingly being used exactly this way — prepping a unit for fire rather than substituting for it.

The second is burn first, then cut. OSU's guidance is to burn before mechanical treatment, which reduces both spot-fire risk and mechanical cost by taking out the small trees so the machinery only has to deal with what's left.

One specific warning is worth repeating because it runs against instinct: do not pile cut redcedar. OSU says to leave cut cedar where it lays to feed the fire that follows, because piles of burning redcedar throw firebrands that travel hundreds of feet downwind and start spot fires. If you've read our firebreak best practices guide, that's the scenario those lines exist to stop — and it's why AgriLife recommends bladed lines to mineral soil at least 12 feet wide, with double lines 100 to 300 feet apart for higher-risk units.

A useful piece of good news: redcedar is a non-sprouter. Cut below the lowest branch and it will not regrow. That's why a single well-executed treatment on a given tree is permanent, and why cedar behaves so differently from sprouting brush like mesquite or oak, where eXtension notes fire frequency of at least every three years is needed to hold resprouters in check.

Burn interval, and what comes after

One burn does not solve cedar. NRCS reports that seeds spread up to 100 yards from parent trees, that cedars stay small and manageable for the first four or five years after a burn, and that growth becomes exponential if left past about eight years. Their recommended range is five to ten years between burns depending on regrowth — which means cedar control is a permanent line item in your grazing plan, not a project you finish.

What you don't have to do is reseed. OSU is explicit: once redcedar is cut or burned, reseeding is unnecessary. Native grasses, forbs, legumes, and woody plants recover on their own given adequate rainfall and proper grazing management. Without those, recovery just takes longer.

The upside is worth stating. NRCS reports experienced ranchers doubling or tripling grazing capacity after a burn and recovery, along with better nesting habitat as native grasses like switchgrass and bluestem return, and incidental control of invaders like smooth bromegrass and Kentucky bluegrass. A properly timed spring burn also removes thatch, cycles nutrients, and improves water retention — and if you're weighing spring against fall for your unit, our guide to spring vs. fall burning walks through the tradeoffs.

Frequently asked questions

How tall is too tall for fire to kill a cedar?

There's no single cutoff, because it depends on fire intensity and fuel load, but the practical guidance clusters tightly. UNL CropWatch treats burning as an effective option up to about 2 feet, cutting and individual-tree herbicide as the tools from 2 to 10 feet, and cutting as the most economical option above 10 feet. NRCS South Dakota reports that fire will manage two-to-three-foot cedars for eight to ten years and that heavy populations of trees over 8 feet may require mechanical clipping first.

How long do I have to rest a pasture before burning it?

Typically one to two growing seasons. NRCS South Dakota describes ranchers deferring grazing for one to two years to build the fuel load, aiming for roughly 4,000 to 5,000 lbs per acre of biomass. AgriLife notes that in an exceptional forage production year you may be able to take some grazing during part of the preceding year and still carry enough fuel.

Do I need a permit and a written plan?

Almost always, and the plan matters as much as the permit. NRCS South Dakota describes prescribed burn plans that take up to a year to develop, with three to four site visits to map the unit, identify hazards and escape routes, and build an ignition plan — plus liability insurance. Requirements vary widely by state and county, so start with our burn permits by state guide and then confirm locally. A written burn plan is the document that makes the rest defensible.

I've never run a burn. Where do I start?

Prescribed burn associations. NRCS points landowners toward locally led, rancher-organized groups — neighbors helping neighbors conduct each other's burns — as the most successful model for getting inexperienced landowners burning safely. Your local NRCS office can connect you with one. In the meantime, get comfortable reading conditions: our guide to reading a fire weather forecast covers the parameters that decide whether a given day is workable.