Ornamental · Poaceae
Oats
Avena sativa
A quick-growing cool-season grass, all slim green blades and nodding heads, at home as cover in a field, as feed grain, and as cat grass on a bright windowsill.
Full sun
Every 3–7 days
60–120 days
USDA 2–9
Overview
Up close, oats read as a slim green grass of narrow blades and upright stems, and that one plant does the work of many. The same Avena sativa grows as a cover crop, as livestock forage, as the grain in a breakfast bowl, and as the cat grass sold as a tuft of tender shoots for pets to nibble. Only the sowing and management set one use apart from the next.
Oats are a cool-season annual that greens up best in cool, moist weather and fades in heat and drought. The thin blades push up fast, weave into a dense cover that shades out weeds, and draw loose nutrients up into the plant before rain can wash them off. Set beside a slow legume such as peas or clover, the leafy oats stand as a nurse crop over the young plants, then brown off and yield the ground.
As the season turns, each stem lifts an open, drooping, branched panicle of spikelets, and later the plump grain ripens along it. Where winters bite hard, the blades brown and the stems collapse on their own; where they stay soft, the green plant lives on and sheds seed, so it is cut or turned under before those heads ripen. Reading which side of that cold line your ground falls on is the one thing to settle before sowing.
Care
The short version: oats color up best in full sun on cool, moist soil, needing little or no extra feeding. The seed goes straight into the ground, the soil stays moist, and warm winters that keep the green stand alive to reseed are the thing to watch.
Light
Oats color up deepest in full sun and crop best out in the open, where the blades stand upright and green. A little partial shade they take, but past that the stand thins and the leaves pale and weaken.
Water
As a cool-season grass, oats keep their blades green and firm in cool, moist ground and wilt in heat or drought. The soil is kept from drying out, since a dry spell curls and stresses the leaves and thins both the cover and the grain.
Soil
Few cereals prove so adaptable. Oats root best in a well-drained loam but hold their green in poor, somewhat acidic, and even wet ground better than most grains, across a pH from 4.5 to 8.0.
Temperature
This hardy cool-weather grass keeps growing across a wide range, from about 21°F to 84°F (-6°C to 29°C). The thin blades push up from chilly soil and do their fullest, greenest growth before summer heat sets in.
Humidity
Ordinary outdoor humidity keeps the blades in good order, so there is no target figure. Open airflow around the stems matters more, since a crowded, damp stand invites the orange-brown pustules of rust and other leaf diseases.
Feeding
Oats draw very little from the soil, and as a cover or nurse crop they often need no fertilizer at all, especially in a fall or legume-mix sowing. Nitrogen is kept low, since a surplus throws up soft, leaf-heavy stems that lean and lie down.
Pruning
There is no pruning of the plant to speak of. In mild-winter regions the green stand is mowed or tilled before it sets seed to head off weedy volunteers, while in cold climates the blades brown and die on their own and need nothing.
Repotting
none
Size & spacing
Each slim plant rises about 2 to 4 feet (60 to 122 cm) tall on upright stems, taking up only 6 to 12 inches (15 to 30 cm) across. The seed goes in thick, since oats grow as a close green stand rather than spaced apart like a garden vegetable.
When to plant
Oats green up on cool weather and answer to the frost. The seed goes in during late summer to early fall, about 40 to 60 days before the first killing frost so the cold can brown the stand down, or again in early spring. Each stem lifts its branched heads in spring to summer, and the plump grain ripens for harvest by mid to late summer.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: Not typical; direct sown outdoors
- Plant: Late summer to early fall (40 to 60 days before first killing frost, to winterkill) or early spring
- Harvest: Open drooping branched panicle of spikelets in spring to summer; grain harvest mid to late summer
Hardiness
USDA hardiness zones: 2–9
Temperature: down to -46°C
Troubleshooting
Oats show few blemishes, all the more so grown as a short-term cover crop. What does appear tends to color or mark the whole stand rather than a single plant, spotting the blades or bending the stems. Match what shows on the leaves and stems to the entries below and act before it spreads.
Grazing cattle, sheep, and goats grow sick on stressed forage
Nothing in the green blade or the plump grain is itself a poison. When drought, frost, or heavy nitrogen stresses the plant, the leaves and stems store up nitrate, and that nitrate is what sickens grazing ruminants such as cattle, sheep, and goats. Stressed or heavily fed forage is tested before grazing, drought- or frost-stressed stands are left ungrazed, and ensiling brings the nitrate down. The standing plant and the harvested grain stay safe for pets and people.
Fix:
- Test stressed or heavily fertilized forage for nitrate before grazing or feeding
- Ensiling can reduce nitrate levels
- Avoid grazing drought- or frost-stressed stands
Oats stay green through winter and reseed instead of dying back
A mild winter leaves the blades green and the stems standing rather than browning off. The plants push up fresh growth, lift branched seedheads, and shed grain that sprouts the next year. Reliable dieback shows up only in Zone 6 and colder and much of Zone 7. Where the cold is softer, the stand is cut or turned under before those panicles ripen rather than waiting for frost to brown it.
Fix:
- Mow or till the stand before seed set
- Terminate by herbicide or mowing soon after the vegetative stage
- Do not rely on winterkill termination in mild-winter areas
Rust-orange pustules, dark sooty powder, and yellow, shrunken leaves
The marks on the blades tell the disease apart. Crown and stem rust stud the leaves with raised orange-brown pustules, smut coats parts of the plant in dark powdery masses, and barley yellow dwarf virus, carried in by aphids, washes the leaves yellow and red while the whole plant stays short. A season away from other cereals, clean or resistant seed, and aphid control hold it back. Grown as a short-lived cover, the stand seldom carries enough spotting to matter.
Fix:
- Rotate away from cereals
- Use clean, treated, or resistant seed where available
- Control aphids that vector barley yellow dwarf
Tall stems slump over and lie pressed to the soil
Tall, slender stems bending over and pressing flat is called lodging. It follows soil that is too rich or too heavily fed with nitrogen, which throws up soft, leaf-heavy, top-heavy growth that a hard rain or gust presses down. That extra nitrogen is held off oats grown as a cover or nurse crop. When grain is not the aim, the flattened stems are no loss and still mat down over weeds and settle into a mulch.
Fix:
- Avoid extra nitrogen fertilizer when grown as a cover or nurse crop
- Mow tall growth before it lodges if managing biomass
Toxicity
From the tender green shoot to the plump ripe grain, oats are about as safe as a plant gets. The kernels feed people and animals alike, and the soft blades are grown on purpose as cat grass for pets to nibble, so nothing here is poisonous to cats, dogs, horses, rabbits, birds, livestock, or children. The one caveat rests with grazing ruminants, since the leaves and stems of drought- or frost-stressed plants can hold nitrate worth testing for.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
Those slim green blades are the familiar cat grass, grown for cats to nibble. A little chewing on the tender shoots is harmless and can help a cat pass a hairball.
Dogs Safe
Dogs can crop the soft blades without harm, and the same tray of pet grass grown for cats serves them too. Plain oats and oat grass sit on no toxic-plant list.
Horses Safe
The plump grain has fed horses as a feed grain for generations, and they graze the leafy tops without harm. No part of the plant is poisonous to them.
Rabbits Safe
Rabbits do well on dried oat hay and the fresh green grass alike, both a normal part of their diet.
Livestock Safe
The leaves and stems themselves are wholesome forage and hold no toxin. The one thing to watch is nitrate, which can gather in the tissue of oats stressed by drought, frost, or heavy nitrogen, so questionable forage is tested before ruminants graze it.
Birds Safe
The dry grain is a common bird feed, and chickens and wild birds eat the kernels and pick at the green blades.
People Safe
The groat inside the hull is a staple food, eaten as oatmeal, oat flour, and more. The plant is grown for people to eat.
Like other cereal grasses, drought- or frost-stressed oat forage can accumulate nitrates that may harm grazing ruminant livestock, but the plant is not poisonous to pets or people.
Varieties
Oats come in a few types sorted by season and end use, and these are the ones worth telling apart.
Spring oats
The most common kind, sown in spring or late summer, lifting its heads without any cold spell and browning off once hard frost arrives.
Winter oats
Hardier types for mild-winter regions, where the green plants live through the cold and head the following spring.
Forage / hay oat varieties
Types bred for thick, leafy growth, such as ForagePlus, and cut for hay, silage, or grazing rather than grain.
Hull-less (naked) oats
Types that thresh free of the papery hull to leave the bare groat exposed, prized for both feed and food.
Companions
Oats earn their keep beside slow-starting legumes, where they nurse the young plants along and then bow out as the season turns.
Plant near
Field peas: Oats serve as a nurse crop, providing quick weed-suppressing cover and support while the slower legume establishes.
Clover: Oats nurse establishing clover, suppressing weeds and scavenging nutrients while winterkilling to release the legume.
Hairy vetch: Oats added to slow-establishing vetch improve legume survival and provide cover that winterkills in many areas.
How to propagate
Oats rise from seed and nothing else, the hulled kernels sown right where the green stand is meant to grow.
SeedEasy
Late summer to early fall or early spring · Germinates quickly (germinates at about 38 degrees F); usable cover in 6 to 10 weeks
Oats rise from seed alone, the hulled kernels sown straight into the ground in late summer to early fall or in early spring. The seed is drilled at about 60 to 75 pounds an acre or broadcast at 80 to 100 pounds an acre, tucked half an inch to an inch deep. The first thin green blades push up in cool soil down to about 38°F (3°C), and the stand knits into usable cover in 6 to 10 weeks, which is what makes it such a quick, cheap, dependable crop to start.
Myths
Cover-crop oats stand as a plant apart from the oats we eat and the cat grass raised for pets.
The green shoots on the windowsill and the grain in the field are one and the same. Cover-crop oats, forage and hay oats, grain oats, and the grass grown for cats to nibble are all the same plant, Avena sativa. Only the sowing and management differ.
Oats will winterkill and finish themselves off every time, so the stand needs no killing on your part.
The blades brown off and the stems collapse on their own only where winters turn cold enough, roughly Zone 6 and colder and much of Zone 7, down into the low 20s degrees F. In milder regions the green plants push through winter and lift seedheads, so the stand is mowed or tilled before those panicles ripen.