Onions and garlic are two of the most useful crops to grow at home. They take up relatively little space, are easy to care for and can provide a plentiful harvest that lasts well beyond the growing season.
Whether you’re growing in a vegetable patch, raised bed or containers, getting the basics right from the beginning will help you grow healthy bulbs.
But when should you plant onions and garlic? What soil do they need? Can onions and garlic be planted together? And how deep should you plant garlic cloves?
In this guide, we’ll cover everything you need to know about how to plant onions and garlic, from preparing your soil and choosing the right position to planting, watering, harvesting and storing your crop.
When should you plant onions and garlic?
Although onions and garlic are closely related, their planting times depend on the variety you’re growing.
When to plant garlic in the UK
Autumn is generally the best time to plant garlic in the UK. Garlic cloves are usually planted from around October through to early winter.
Garlic benefits from a period of cold weather, which helps the cloves develop into good-sized bulbs. Most varieties need around one to two months of cold temperatures for good bulb development.
Some varieties are suitable for planting in late winter or early spring, so always check growing instructions or the variety you have chosen.
If you’re planting garlic this autumn, choose garlic bulbs specifically sold for planting rather than supermarket garlic. Planting garlic from a garden centre gives you access to varieties selected for growing and harvesting in the UK.
When to plant onions
Onions can be planted at different times depending on the type you choose.
Spring planted onion sets are generally planted in early to mid spring and harvested during summer and early autumn. There are also overwintering onion sets, which can be planted in autumn for an earlier harvest the following year.
If you’re planting onions in autumn, make sure you choose an overwintering variety. Don't assume all onion sets are suitable for autumn planting.
Where is the best place to plant onions and garlic?
Both onions and garlic prefer a warm sunny position with well drained soil.
Choose a spot that receives plenty of direct sunlight throughout the day. Good light encourages strong foliage growth, which is important because the leaves help provide the energy needed to develop the bulbs.
Your planting area should ideally be:
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Sunny and open
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Well drained
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Free from persistent weeds
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Protected from waterlogging
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Easy access for watering and weeding
If you’re preparing a new vegetable bed, take some time to plan where your crops will go before planting. Our allotment guide has more advice on planning growing areas, preparing beds and choosing the right tools for your vegetable garden.
Can you plant onions and garlic together?
Yes, onions and garlic can be grown in the same vegetable garden or raised bed because they have similar requirements.
Both enjoy sunny conditions, fertile soil and good drainage, so they can be convenient crops to grow alongside each other.
However, onions and garlic are both members of the allium family, so it is important to think about crop rotation. Try not to grow allium in exactly the same part of the garden year after year, as this can increase the risk of certain soil-borne pests diseases building up.
Are onions and garlic good companion plants?
Onions and garlic are often included in companion planting plants because their strong scent is thought to make it harder for certain pests to locate neighbouring crops.
However, companion planting shouldn’t be relied upon as a guaranteed method of pest control. Instead, think of it as one part of a healthy and diverse growing space.
You can find more ideas for pairing vegetables with other plants in our companion planting guide.
What soil do onions and garlic need?
Getting the soil right is one of the most important parts of learning how to grow onions and garlic.
Both crops prefer fertile, free draining soil. Garlic in particular doesn’t cope well with waterlogged conditions, especially when planted over winter. Wet soil can increase the risk of disease and bulb rot.
Ideally, your soil should be:
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Well drained
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Fertile
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Loose and workable
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Rich in organic matter
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Relatively free from stones and weeds
A slightly acidic to neutral soil is suitable, with garlic performing best where the soil isn’t strongly acidic. A pH of around 6.5 in recommended as a good general purpose garden soil level for garlic
If you’re unsure about your soil, a simple soil testing kit can help you understand it pH before you make any amendments.
How to improve your soil for onions and garlic
If your soil is poor, compacted or lacking organic matter, improve it before planting.
Adding well rotted organic matter can help improve soil structure while adding nutrients. For garlic it is recommended to incorporate around two bucketfuls of well-rotted manure or homemade garden compost per square metre before planting.
For your own vegetable beds, a peat free compost such as Miracle-Gro organic fruit and veg peat free compost that is specifically aimed at fruit and vegetable growing is suitable, or a Levington organic blend farm manure can be used to improve soil structure and fertility.
Top Tip: Don’t use fresh manure directly around newly planted bulbs. Well rotted manure or compost is a much better option when preparing your growing area.
What tools do you need to plant onions and garlic?
You don’t need a huge collection of gardening equipment to grow onions and garlic, but a few basic tools will make planting much easier.
A digging spade or garden fork is useful for preparing the soil, while a hand trowel is ideal for smaller planting jobs.
A dibber is particularly useful for garlic because it allows you to quickly make holes to a consistent depth. If you’re planting lots of onion sets, a bulb planter can also speed things up.
Don't forget a good pair of gardening gloves when preparing soil and handling compost.
How to plant garlic
Once you’ve prepared your soil, planting garlic is straightforward.
Step 1: prepare the soil
Start by removing weeds and any large stones from your planting area.
Use a garden fork to loosen compacted soil without leaving large clumps. If the soil needs improving, incorporate well rotted compost or manure before planting.
The aim is to create loose, well drained soil that the garlic roots can establish in easily.
Step 2: separate the garlic bulb
Take your planting garlic and carefully separate the bulb into individual cloves.
Don't peel the cloves. Keep their papering outer skin intact, as this helps protect them after planting.
Choose the largest, healthiest cloves for planting where possible.
Step 3: plant the garlic cloves
Plant each clove with the pointed end facing upwards and the flat root end facing downwards.
Plant the cloves approximately 2,5cm below the soil surface, with around 15cm between each clove and approximately 30cm between rows.
If you’re planting in lighter soil, you can plant a little deeper. However, avoid planting garlic too deeply in heavy soil as poor drainage can become a problem.
A dibber makes this particularly easy because you can create a series of evenly spaced holes before dropping in your cloves.
Step 4: protect newly planted garlic
Birds can sometimes pull newly planted cloves out of the ground before they’ve rooted.
If this is a problem in your garden, cover the newly planted area with suitable horticultural fleece or plastic free netting until the cloves are established.
How to plant onion sets
Onions are often grown from sets, which are small immature onion bulbs.
They’re one of the easiest ways for beginners to grow onions because they’re quicker and generally simpler than growing onions from seed.
Step 1: prepare your growing area
Choose a sunny position and remove weeds before planting.
If your soil needs improving, add well rotted compost or organic matter ahead of planting.
A hand fork or garden fork is useful for loosening the soil, while a rake can help create a level, crumbly planting surface.
Step 2: plant the onion sets
Make a shallow hole or drill approximately 2cm deep.
Place each onion set into the soil with the pointed tip facing upwards, leaving the tip facing upwards, leaving the tip just visible above the soil surface.
A hand bulb planter is useful if you’re planting a large number of sets, as it allows you to make consistent planting holes quickly.
Step 3: space your onion sets
Space onion sets around 5cm to 15cm apart, spending on the size of bulbs you want to grow.
Giving plants more space generally allows them to develop larger bulbs, while closer spacing produces more but smaller onions.
Leave around 20cm to 30cm between rows to make weeding maintenance easier.
Growing onions and garlic in containers
Don't have a vegetable patch? You can grow both onions and garlic successfully in containers.
This is particularly useful if you have a patio, balcony or small garden where you’re short on growing space.
Growing garlic in pots
Choose a container with good drainage and at least 25cm of depth.
Fill it with quality peat-free multi purpose compost and plant the cloves at the same depth and spacing as you would in the ground.
Remember that containers can dry out more quickly than garden soil, so check them regularly.
Growing onions in pots
Onions can also be grown in large containers, around 45cm wide and deep.
Choose a sunny position and use a quality peat free compost.
Make sure your container has adequate drainage holes. Waterlogged compost can cause bulbs to rot, particularly during wet weather.
How to care for onions and garlic
Once planted, onions and garlic don't need constant attention, but keeping on top of a few simple jobs will help produce a better crop.
Keep the soil weed free
Weeds compete with onions and garlic for water, nutrients and light.
Because both crops have relatively narrow leaves, they don't create much shade over the surrounding soil, meaning weeds can quickly establish themselves.
Regularly remove weeds by hand or use a hand fork or hoe carefully around plants.
Water during dry weather
Both crops need water while actively growing particularly during prolonged dry spells.
Water deeply when necessary rather than giving plants frequent, small amounts.
A watering can or hose makes this easier, particularly if you’re growing in raised beds or containers.
As the bulbs mature, reduce watering. Garlic in particular should not be kept excessively wet once the bulbs have formed.
Avoid overfeeding
Good soil preparation should provide much of the nutrition your onions and garlic need.
Avoid excessive amounts of high nitrogen fertiliser, which can encourage lots of leafy growth at the expense of bulb development.
If your soil is poor, choose a suitable vegetable feed and always follow the instructions on the packaging.
When are onions and garlic ready to harvest?
After months of growing, knowing when to harvest is the final step.
When to harvest garlic
Garlic is generally ready to harvest from late spring through summer, depending on the variety and when it was planted.
As the bulbs mature, the leaves will turn yellow and die back.
Once the bulbs are well formed, reduce watering and allow the foliage to naturally dry.
Carefully lift the bulbs from the soil, taking care not to damage them.
When to harvest onions
Autumn planted onion sets can be ready from around June and July, while spring planted sets are generally harvested from July onwards into early autumn.
Yellowing and toppling foliage is a sign the onions are approaching maturity.
Carefully lift them from the soil using a garden fork, taking not to bruise or damage the bulbs.
How to dry and tire onions and garlic
One of the biggest benefits of growing onions and garlic yourself is that, once properly dried, you can store much of your harvest for later.
How to store onions
After harvesting, onions should be allowed to dry thoroughly for around two weeks.
Place them somewhere dry and well ventilated, allowing plenty of air to circulate around the bulbs. Once the foliage is papery and dry, store onions in net bags, trays or another breathable container.
Keep them somewhere cool, dry and well ventilated.
How to store garlic
Garlic should also be dried thoroughly after harvesting.
Once the outer skin has dried and the foliage is completely dry, store the bulbs somewhere cool, dry and well ventilated.
Check your stored bulbs regularly and remove any that show signs of mold or rot.
Common problems when growing onions and garlic
Why are my garlic bulbs rotting?
The most likely culprit is excessive moisture.
Garlic needs well drained soil, particularly when planted over winter. If your soil becomes waterlogged, consider improving drainage or growing garlic in raised beds or containers.
Why aren’t my onions forming large bulbs?
Small onions can be caused by several factors, including overcrowding, poor sunlight, competition from weeds or unsuitable growing conditions.
Make sure your plants have enough space, receive plenty of sunlight and aren’t competing with weeds.
Why are my onions flowering?
Onions can sometimes bolt, meaning they produce a flower stem instead of putting their energy in bulb development.
Cold conditions and certain varieties can increase the risk of bolting. Choosing suitable varieties and providing good growing conditions can help reduce the likelihood.
Birds keep pulling up my sets, what can I do?
Newly planted onion seats and garlic cloves can be disturbed by birds. Covering the planting area with suitable fleece or netting until the plants are established can help prevent this.
Growing your own onions and garlic is a rewarding way to make better use of your garden, and you don’t need a huge amount of space to get started.
The key is to choose the right variety plant at the appropriate time and provide sunny conditions, fertile soil, and excellent drainage.