Most tree advice is about how to make the cut. With oaks in Texas, the more important question is when, and it is the part homeowners almost never hear before the saw comes out.

When to trim oak trees in Houston: the short answer

The best time to trim an oak in Houston, and anywhere else in Texas, is fall and winter, roughly October through January. Texas A&M Forest Service puts it plainly: “pruning or wounding trees should be avoided from February through June and no matter the time of year, all oak tree wounds should be painted immediately.” Its oak wilt flyer on texasoakwilt.org gives the exact dates as February 1 to June 30, and its pruning calendar adds that summer heat can stress a freshly cut oak, so unless a limb is a safety problem, the Forest Service says to wait for fall and winter.

Source: Texas A&M Forest Service, “Prevent the spread of oak wilt in Texas”, February 4, 2025.

What oak wilt is

Oak wilt is a fungal disease that moves through an oak’s water-conducting tissue. The tree responds by trying to wall the infection off, and in doing so it chokes off its own water supply. The canopy browns and thins, and on the most vulnerable species the tree can be dead within weeks of showing symptoms.

Texas A&M Forest Service calls it one of the deadliest tree diseases in the country. It has killed oaks in 76 Texas counties.

The two ways it travels

This is the part that makes the calendar make sense.

Above ground, by beetle. Infected trees produce fungal mats that give off a smell sap-feeding beetles find attractive. Those beetles land on the mat, pick up spores, and then go looking for the next sweet-smelling thing available. A fresh pruning cut on a healthy oak is exactly that. The beetle walks across the open wound and the tree is infected.

Below ground, by root. Oaks of the same species growing near each other commonly graft their roots together. Once one tree in a grafted group is infected, the fungus can move tree to tree underground with no insect involved at all. This is why oak wilt tends to spread outward through a neighborhood in a widening patch rather than popping up randomly.

You cannot do much about the roots after the fact. You have complete control over the beetle route.

The calendar

February 1 through June 30: do not prune oaks. That window is when fungal mat production is highest and the beetles are most active at the same time. A cut made in March is the single most avoidable way to infect a healthy tree.

July through January: the safer window. Beetle activity and mat production are both low. This is when routine oak pruning should be scheduled.

That makes late summer through winter the right time for the oak work most people put off, and it is why we tell customers who call us in March about a non-urgent oak that we would rather come back.

The exception, and the rule that covers it

Storms do not read the calendar. A limb hanging over a driveway in April has to come down in April.

So the standing rule is: paint every oak wound immediately, in any season. Pruning paint is not generally recommended on most trees, and that is where the confusion comes from. On oaks in Texas it is the recommended practice specifically because it seals the wound against beetles before they can find it. Immediately means within minutes, not when the crew finishes the job.

Any pruning sealer or latex paint works. What matters is that the surface is covered before the wound has time to advertise itself.

Oak trimming month by month in Houston

The Forest Service publishes one oak wilt pruning calendar for the whole state. Here is how it lines up with a Houston year. Where a line quotes the calendar, the words are the Forest Service’s own.

January. Still a good month for oak work. The calendar’s January note is “Wrap up your tree pruning,” because the no-prune window opens on February 1.
February through June. Leave oaks alone. The calendar says beetles that carry the spores “are most active February-June” and to “avoid pruning/wounding oaks February-June if possible.” A storm-broken limb still comes down, and the cut gets painted right away.
May. The calendar flags this as the month oaks “typically show symptoms of oak wilt.” A good time to look at your trees, not to cut them.
July. According to the calendar, “beetles and fungal mat activity decrease with high temperatures.” The oak wilt risk drops, but a Houston July is hard on a tree.
August and September. The calendar’s August advice is that pruning in the heat of summer “can stress the tree” and to “wait until fall/winter to tackle pruning unless safety is a concern.” A hot Houston September usually earns the same patience.
October. In the calendar’s words, “Now is a good time to prune your trees, but always paint oak wounds immediately!” This is where most routine oak trimming belongs.
November and December. Still the safe season. The calendar’s December reminder is “Don’t move firewood,” which matters if a dead red oak came down this year.

Two things hold in every month: paint every oak cut the day it is made, and avoid wounding the tree in other ways too. The Forest Service lists lawnmowers, string trimmers, construction and storms among the wounds that can let the disease in.

What to watch for

Symptoms vary by species, and live oaks are the ones most people around here have.

Live oaks typically show veinal necrosis: the veins of a leaf yellow or brown while the tissue between them stays green longer. It is distinctive once you have seen it. Leaves drop while still partly green.
Red oaks (Shumard, water oak, willow oak) usually go faster and less subtly, with the canopy browning from the top down. Red oaks are the species that produce the fungal mats, which makes a dying red oak a live source of infection for everything around it.
White oaks are generally more resistant and slower to decline.

A tree that browns out over one summer from the top down, in a yard where a neighbor lost an oak last year, is worth having looked at rather than waited on.

What actually helps

Do not move firewood from a dead oak. A red oak that died of oak wilt can carry fungal mats in the cut wood. Moving that wood moves the disease. Burn it where it fell or have it chipped.

Take out an infected red oak promptly. It is not sentimental advice. A standing infected red oak is producing the mats that infect everything else on the block.

Root barriers are a real tool but a serious one. Trenching to sever root grafts around an infection center is the standard containment approach, and it is a job that needs the infection center identified correctly first. It is not a first step.

Injection exists. Fungicide treatment can protect high-value uninfected oaks near a known infection center, and it is expensive enough that it belongs to specimen trees rather than a whole yard.

Common questions about oak trimming season in Texas

What are the oak wilt season dates in Texas?

February 1 through June 30. Texas A&M Forest Service’s oak wilt flyer says to “avoid pruning oak trees from February 1 to June 30” (texasoakwilt.org). The Forest Service gives one set of dates for Texas, and we hold to them on every oak we work on, from Houston to Conroe.

When should I trim the oak trees in my Houston yard?

Fall and winter, October through January, is the stretch the Forest Service’s pruning calendar points to, with October called “a good time to prune.” July is outside the oak wilt window, but the calendar suggests waiting out the summer heat unless a limb is a safety concern.

Is it OK to trim a live oak in the summer in Texas?

Live oaks follow the same calendar as every other oak. July and August are outside the February through June window, and the Forest Service calendar notes that beetle and fungal mat activity drop in the heat. It also says summer pruning “can stress the tree.” Light safety work is reasonable; a big shaping job can wait for October. Either way, the cuts get painted.

Can I trim an oak in the spring if a limb is dangerous?

Yes. The Forest Service’s guidance allows pruning in the February through June window when it is “a necessity for safety purposes,” with one condition: “make sure to paint all oak wounds immediately” (pruning calendar). Any type of paint works, according to its flyer.

Where we come in

Most of what we do about oak wilt is timing and discipline. We schedule non-urgent oak pruning outside the February-through-June window, we paint every oak cut on the spot regardless of the month, and we tell you plainly when a tree is worth treating and when the honest answer is that it is already gone.

If an oak on your property is thinning at the top, dropping green leaves, or standing near one that died last season, get it looked at while the options are still open. Serving Houston, Conroe, The Woodlands, Spring, Tomball, Cypress, Kingwood and Katy.

Sources: Texas A&M Forest Service and Texas A&M AgriLife Extension guidance on oak wilt identification, pruning timing and management.

Oak trimming calendar sources: Texas A&M Forest Service, “Prevent the spread of oak wilt in Texas” (February 4, 2025); texasoakwilt.org, Oak Wilt in Texas flyer and Pruning Calendar for Oak Wilt Prevention.

Oak Wilt in Texas: Why the Month You Prune Matters