Tree · Fagaceae
Northern Red Oak
Quercus rubra
A forgiving native that pays you back with deep shade and brilliant red fall color for generations.
Full sun
Every 7–14 days
USDA 3–8
50–75 ft · 15.2–22.9 m
Overview
If you have space and a little patience, northern red oak is one of the friendliest big trees you can plant. It comes from the beech family and grows wild across eastern North America, climbing to 50 to 75 feet (15 to 23 m) with a wide, rounded crown that throws welcome shade. You will know it by the long pale ridges in its bark and the pointed, bristle-tipped leaf lobes that mark it as a true member of the red oak group.
Here is the reassuring part: red oak grows faster than most of its cousins, so you will not be waiting a lifetime for shade. That speed is why towns line streets and parks with it, and it copes gracefully with city soil and road grit that would trouble fussier natives. When the nights turn cold, the whole canopy warms to a russet and brilliant red that makes the wait feel worthwhile.
Give it room and the acidic ground it likes, and after the first few years this tree pretty much looks after itself, which is a comfort if you are new to trees. The one thing to keep in mind is that the acorns and young leaves carry tannins that are hard on grazing animals, so red oak is happiest in a yard or park rather than out in a pasture. Do not let that worry you, since a tree in a garden is easy to enjoy safely.
Care
The short version: give it full sun and deep, acidic, well-drained soil, keep it watered through its first few years while the taproot settles, and after that your oak will look after itself.
Light
Red oak is happiest in full sun, which helps it grow straight and full, though a young one will put up with some partial shade while it finds its feet. Given plenty of light, it settles into the broad, even crown that makes such a generous shade tree.
Water
For the first few years, keep a young tree watered while its roots push down, letting the top half of the soil dry out between drinks so it never sits soggy. Once it has settled in, red oak turns pleasantly drought tolerant and gets by on rainfall except in the harshest dry spells.
Soil
Plant it in deep, fertile, well-drained soil that leans acidic, somewhere in the range of a pH of 4.5 to 7.0. It is not fond of alkaline ground, where its leaves can yellow with iron chlorosis, so a moist loam or sandy loam will keep it happiest.
Temperature
Cold does not faze this tree, which shrugs off winters down to -40°F (-40°C) and takes summer heat up to about 100°F (38°C). That comfortable range covers a broad sweep of the temperate zone.
Humidity
Plain outdoor air is all your oak asks for, so there is no humidity reading to fuss over. What helps more is good airflow through the canopy, since still, damp air is what gives leaf fungi their opening.
Feeding
An established landscape oak almost never needs feeding, which is one less thing to worry about. If your soil is truly poor, a balanced slow-release tree fertilizer in early spring is plenty, and there is no need to do more.
Pruning
Prune only in the quiet of the dormant winter months, and never from April through June, when fresh cuts invite the beetles that carry oak wilt. Take out any dead, damaged, or crossing branches, then let the tree get on with things.
Repotting
There is really no repotting here, because red oak grows into a forest-sized tree. Move it only while it is young, before that deep taproot anchors down, and settle it in a spot where it can stand for the rest of its long life.
Size & spacing
A grown red oak stands 50 to 75 feet (15 to 23 m) tall and spreads 40 to 65 feet (12 to 20 m) wide, so it needs a generous, open spot. Give it plenty of clearance from buildings and power lines and it will thank you for the room.
When to plant
Red oak keeps close time with the seasons, and that makes planning easy. Acorns fall in autumn and need a cold winter before they will sprout, so sow them then or set out young saplings in early spring. Save any pruning for the depth of winter, which keeps oak wilt from finding fresh cuts.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Stratify acorns over winter (60-90 days cold-moist) and sow in deep containers in late winter to early spring
- Plant: Plant acorns in fall or transplant young saplings in early spring
- Harvest: Inconspicuous yellow-green catkins in spring; acorns mature over two growing seasons and drop in fall
Hardiness
USDA hardiness zones: 3–8
Temperature: down to -40°C
Troubleshooting
An established red oak is a tough, healthy thing, and most of what troubles it shows up first on the leaves. Only oak wilt really needs your quick attention, while the rest tend to be cosmetic or clear up on their own. Find your symptom below and act while it still makes a difference, and try not to panic.
Leaves bronzing from the edges while the crown thins fast
This one is oak wilt, a fungus that seals off the tree's water-carrying vessels from within, and red oaks have very little natural defense against it. Leaves lose their color, bronze inward from the margins, and fall while the top of the crown thins, sometimes killing a tree in one summer. Have a lab confirm it, take the tree down without delay, and cut the grafted roots that link one oak to the next so the disease cannot creep along underground.
Fix:
- Remove and properly dispose of infected trees promptly
- Sever root grafts between adjacent oaks to limit underground spread
- Avoid wounding or pruning healthy oaks April-June
Brown patches tracking the veins after a chilly, damp spring
The good news with oak anthracnose is that it looks scarier than it is. This leaf fungus wakes up when spring drags on cold and wet, painting brown blotches along the veins, curling the fresh leaves, and nipping off a twig here and there, yet a settled tree rarely comes to harm. Gather and burn the fallen leaves, trim away the dead twigs, and open up the canopy so air can move through.
Fix:
- Rake and destroy fallen infected leaves
- Prune out dead twigs
- Apply labeled fungicide early in the season before bud break only in severe cases
Chewed, stripped leaves and caterpillars working the canopy
Spongy moth caterpillars, the pest once known as gypsy moth, can chew a crown bare by late spring, which is alarming to see. Take heart though, because a healthy oak brushes off a single bad year and simply pushes out a fresh flush of leaves. Scrape the egg masses from the bark in winter, wrap a sticky band or pick the caterpillars off by hand in small outbreaks, and keep the tree watered while it recovers its leaves.
Fix:
- Hand-pick or use sticky bands on trunks for small infestations
- Apply Bacillus thuringiensis (Bt) to young larvae
- Support tree vigor with water during defoliation years
Yellowing leaves with still-green veins on new growth
When the newest leaves go yellow but their veins stay green, the cause is usually iron chlorosis, which sets in where the soil is too alkaline for the roots to take up iron. The color drains from the leaf between the veins, worst on the freshest growth at the tips. Nudge the pH down slowly with elemental sulfur and give a suffering tree some chelated iron, though the surest fix is simply starting it off in acidic ground.
Fix:
- Lower soil pH with elemental sulfur over time
- Apply chelated iron as a soil drench or foliar spray
- Improve soil drainage and aeration
Toxicity
This is a lovely tree to enjoy at a little distance if animals share your space. Its leaves, buds, and green acorns hold tannins that upset the stomach and, in horses and livestock, can harm the kidneys badly enough to be fatal. People should skip raw acorns too, since they stay bitter until leached, so the kind thing is to keep grazing animals, pets, and small children away from anything that drops.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Mild
A curious cat that tastes a leaf or an acorn will most likely end up with a queasy stomach, some vomiting, loose stools, and little appetite for a day. Cats seldom swallow enough to be truly hurt, so a quick sweep of any fallen acorns from a favorite lounging spot is really all it takes.
Dogs Mild
Dogs are the pets most tempted to crunch down a few acorns, and doing so tends to bring vomiting, diarrhea, and a flagging appetite. A load of whole acorns can also jam up and block the gut, so it pays to rake them from any yard where a dog likes to root around.
Horses Severe
Horses suffer badly from oak, so this is one to take seriously. Eating young leaves, buds, or green acorns can cause belly pain, constipation that gives way to bloody diarrhea, a listless mood, frequent urination, dark urine, jaundice, and kidney damage that can prove fatal.
Rabbits Toxic
A rabbit's gut simply cannot handle the tannins packed into oak leaves and acorns, so keep every part of the tree well away from the hutch. Even a nibble can leave a rabbit off its food and clearly unwell.
Livestock Severe
Cattle, sheep, and goats that browse young oak leaves, buds, or green acorns can end up with ulcers through the gut and failing kidneys as the tannins pile up inside them. A large enough helping can be fatal, and animals will actively hunt for acorns after a storm brings them down, so fence them off.
Birds Caution
Wild jays and woodpeckers eat acorns happily as part of their natural fare, but those raw tannins are hard on backyard poultry and pet cage birds. To stay on the safe side, keep companion birds away from the leaves and green acorns.
People Caution
Raw acorns taste bitter and drying from their tannins, so none should ever be eaten straight from the tree. The old remedy is a long soak and leaching in water, and it is worth gently steering small children away from putting acorns or leaves in their mouths.
Keep livestock and horses away from oak leaves, buds, and fallen green acorns; pick up acorns where pets forage. Most poisoning occurs when animals eat large amounts.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Nearly every red oak you meet will be the plain species, and that is honestly all you need. Still, a couple of named selections show up here and there if you go looking.
Aurea
The new leaves of Aurea unfurl a warm golden yellow and mellow to green as they age, though it is a hard one to track down for sale.
Splendens
Splendens was chosen for the clean, brilliant red it turns each fall.
How to propagate
Growing red oak from its own acorns is genuinely satisfying and not hard at all. The only trick is to honor the cold rest the seed needs before it will wake up and sprout.
SeedModerate
Collect ripe acorns in fall; sow outdoors immediately or stratify over winter and sow in spring · Germinates the spring after cold stratification; several years to establish a sapling
Red oak takes to growing from acorns kindly, as long as the seed gets the cold winter it expects first. Collect plump, ripe acorns in fall and either sow them outdoors right away or hold them through 60 to 90 days of cold, moist stratification near 32°F to 40°F (0°C to 4°C) before spring sowing. They sprout the following spring and take a few years to grow into a sturdy sapling, so because the tree sends down a deep taproot, plant it where it will stay for good or shift it only while young in a deep container.
Myths
Fallen oak leaves and brown acorns stay equally poisonous to livestock the whole year round.
In truth the risk sits mostly in spring's young leaves and buds and in the green, unripe acorns, where the tannins run highest. The brown leaves that come down in fall carry far less, and a real poisoning takes a big feed rather than a stray mouthful. What matters is timing and how much an animal eats, not merely that an oak is present.
Red oak is too slow-growing to be worth planting for shade.
Not so, since northern red oak is among the faster oaks and puts on genuine height at a moderate to fast clip. A long-lived native like this pays for itself as a shade and street tree, and you will wait far less than its reputation warns.