Oats in the Garden: Sowing, Green Manure, Cat Grass and Harvest

Oats in the garden as green manure, cat grass and for grain: sowing time and depth, digging in, the difference between common, naked and wild oats, and harvesting by hand.

In short: Common oat is a spring cereal that you grow in the garden mainly as green manure, cat grass or for a few handfuls of your own grain. It is sown from March to April 3–4 cm deep, tolerates poorer and more acidic soil, but needs enough moisture. The grain ripens in July to August.

Latin name	Avena sativa, grass family
Sowing for grain	March–April, as soon as the soil can be worked
Depth and rows	3–4 cm, rows 12–15 cm apart
Seed rate	about 15–20 g per m² (400–500 grains)
From sowing to harvest	roughly 4 months
Cat grass	10–15 cm in 7–10 days

Oats are among the least demanding cereals. In the garden, however, hardly anyone grows them for porridge oats. Much more often they serve as a quick green manure between two crops, as grass for cats indoors or as an experiment for children who want to see how grain grows.

In this article you will find the method for all three cases and the differences between common, naked and wild oats, which are often confused.

Common, Naked and Wild Oats: Which Is Which

Oat	What it is good for	How it differs
husked common oat (Avena sativa)	green manure, cat grass, feed	grain tightly enclosed in husks, a mill has to hull it to make oat flakes
naked (hull-less) oat	your own grain and flakes	the husks separate during threshing, the grain is clean
bristle oat (Avena strigosa)	green manure	grows fast, tillers densely, not grown for grain
wild oat (Avena fatua)	nothing, it is a weed	the grains fall out by themselves when ripe and infest the field for years

If you want your own grain for the kitchen, look for naked oat seed. You cannot hull husked oats at home or make flakes from them. For green manure and cat grass, on the other hand, it does not matter which common oat you use.

Sowing Oats Step by Step

An old saying goes "oats into the mud, barley into the dust". Oats are sown as early as possible in spring into moist soil, because they need a lot of water when they tiller and come into ear.

Timing: March to April, as soon as the soil dries enough not to stick to tools. Late sowing in May suffers from drought and rust.
Preparation: dig or loosen the bed and level it. Oats tolerate poorer and slightly acidic soil and do not need farmyard manure.
Sowing: in rows 12–15 cm apart, grains 2–3 cm apart, depth 3–4 cm. About 15–20 g of seed per m².
Firming: press the soil down after sowing with a rake or a board, the grain must be in contact with moist soil.
Protection: cover the sowing with netting or fleece straight away, otherwise pigeons and sparrows will peck out the grain.
Care: weed in the first weeks, water in a dry May. Oats emerge in 1–2 weeks depending on temperature.

Oats as Green Manure

Oats are one of the most practical green manures for the garden. They quickly form a dense stand, their roots loosen the soil and hold nutrients that rain would otherwise wash out. A general overview of green manure crops is in the article Green manure – how to improve the soil without chemicals.

In spring sow them on a bed where you will plant tomatoes, peppers or cucumbers in May to June. Cut them and dig them in before planting.
In summer sow them after harvesting early potatoes, onions or peas, up to the end of August.
Digging in: at the latest at the start of heading, usually 6–8 weeks after sowing. After that the stalks harden and decompose less well. Sow or plant into the dug-in bed only after about a month.
Over winter: a summer sowing does not survive stronger frosts. Leave the dead stand lying as mulch and just dig it in in spring.

A big advantage of oats is that they do not belong to the brassica family. Mustard or oilseed rape after cabbage, kohlrabi and radishes keep the clubroot pathogen in the soil, oats do not. Oats, phacelia or legumes therefore belong on such beds. Oats combine well with vetch or peas, which enrich the soil with nitrogen.

Cat Grass from Oats

Most cats like to nibble young grass, and oats are ideal for this because they grow fast and have soft leaves.

Fill a bowl or a low pot with 3–4 cm of substrate and moisten it.
Scatter the grains densely, almost grain next to grain, and cover with 0.5–1 cm of substrate.
Keep moist at 18–22 °C. The first leaves appear in 2–4 days.
In 7–10 days the grass is 10–15 cm tall and you can give it to the cat.
Start a new bowl every 2–3 weeks, older grass turns yellow and goes mouldy in waterlogged substrate.

If you have a cat, also watch the scents in the home. Which essential oils are risky for cats is described in the article Essential oils and pets. You can grow other microgreens in a similar way to cat grass, the method is in the article Microgreens and sprouts.

Harvesting Grain on a Small Area

Oats flower in June, when sparse drooping panicles emerge from the leaves. The grain ripens gradually from the top of the panicle downwards, and so it is harvested a little before the whole stand is dry.

Harvest at yellow ripeness, in July to August. The stalks are yellow, the grain can be squashed with a fingernail but is no longer milky.
Cut the stalks with a sickle or scissors, tie them into sheaves and leave them to dry for another 1–2 weeks under cover.
Thresh them in a sack or on a sheet by beating, or by rubbing between the palms.
Winnow the grain, for example in the wind or in front of a fan, so that the husks and chaff blow away.
Store only completely dry, in a paper bag or a jar in a dry place.

From a square metre you will harvest in the order of tens of decagrams of grain. That is enough for a cup of flakes, not for a supply.

Most Common Problems

Birds: they peck out the grain after sowing and before harvest. Netting is the only reliable protection.
Drought: late sowing and a dry May mean a low, sparse stand.
Lodging: after over-feeding with nitrogen and in rain the stalks break. Do not fertilise oats.
Rust and mildew: they appear mainly in late sowings in a warm, damp summer. Early sowing and a thinner stand help.
Wild oat: if you find it in the garden, pull it out before it ripens, otherwise it will spread.

Frequently Asked Questions

When are oats sown?

For grain in March to April, as early as the soil allows. As green manure from spring until the end of August.

How long do oats take to grow?

From sowing to grain harvest roughly 4 months. As green manure they are dug in after 6–8 weeks, cat grass is ready in 7–10 days.

How do I grow cat grass from oats?

Sow the grains densely in a bowl of substrate, cover with 0.5–1 cm and keep moist at room temperature. In 7–10 days the grass is 10–15 cm tall.

Can oats be sown for winter?

Spring oats are grown here. A stand sown in summer does not survive stronger frosts, which is useful for green manure, because it turns into winter mulch.

Are oats a good green manure?

Yes, they quickly cover the soil and the roots loosen it. They are especially suitable after brassicas, where brassica mustard would encourage clubroot.

Sources

Updated: 27 September 2026

Author: Jana Vránová, editorial name of the Pěstík.cz team. She writes about the garden, herbs and essential oils. We take safety and dosage information from specialist literature and official sources, which we list for every article.