A member of the onion family, this staple of Mediterranean cooking is simple to grow in a warm sunny site with well-drained soil. It is grown from cloves, which are best planted in late autumn, and is ready to harvest the following summer.
Jobs to do now
- Plant individual cloves
- Cover with horticultural fleece to deter birds
Month by month
Garlic is grown by planting individual cloves of garlic (rather than sowing seeds), usually in autumn – see Plant, below, for full details.
Garlic is generally trouble free and needs little maintenance, apart from watering in dry spells, and regular weeding. Also snip off any flower stems that start to form.
Water garlic during dry spells in spring and early summer, to improve bulb size. However, don’t water once the bulbs are large and well formed, as this could encourage rotting. Yellowing foliage is a sign that the bulbs are reaching this stage of maturity.
Try to avoid overhead watering, as it can encourage fungal diseases.
Garlic plants need full sun, so keep weeds at bay to ensure plants don’t get shaded. Weeding is best done by hand, as hoeing risks damaging the developing bulbs. To avoid the need to weed regularly, consider planting through black plastic sheeting or weed-suppressing membrane.
What to plant
Always buy named varieties of garlic from a garden centre or mail-order supplier. It is best not to plant garlic from a supermarket – it may carry diseases and be unsuitable for the British climate, so results may be disappointing.
There are many varieties of garlic to choose from – look in particular for those with an RHS Award of Garden Merit (AGM), which shows they performed well in growing trials – see our list of AGM fruit and veg.
There are two main types of garlic – hardneck and softneck.
Produces fewer, larger cloves, covered with a looser tunic
Has a stronger, more interesting flavour
Stores only until mid-winter
Often produces flower stalks
Produces smaller, more tightly packed cloves
Stores for longer – if planted in autumn it will keep well into the following winter, if planted in spring it will keep until the middle of the following spring
Does not produce flower stalks unless stressed
Elephant garlic (Allium ampeloprasum) is often sold as garlic, but is actually more closely related to leeks. It produces a small number of very large cloves with a mild flavour. It needs a long, warm growing season to produce a good crop and is best planted in October.
The cloves sometimes don’t divide, producing just slightly larger single-clove (solo) bulbs. Early planting often reduces the occurrence of solo bulbs. The single-clove bulb can be harvested and either eaten or planted again the following autumn, when it will often produce segmented cloves.
Where and when to plant
Garlic needs a period of cold, so is usually planted in late autumn or early winter. Most varieties need one to two months at 0–10°C (32–50°F) for good bulb development. However, some cultivars are suitable for planting in early spring.
If your soil is heavy and damp over winter, it’s better to start garlic off in modules in a coldframe before planting out in spring.
Garlic likes a sunny, well-drained site. Wet soil and/or high humidity around the foliage can make plants more prone to disease, particularly if planted in autumn. Garlic doesn’t thrive in acid soil (below pH 6.5), but you can reduce acidity by applying lime in autumn and winter.
How to plant
Prior to planting, remove any weeds then improve the soil’s structure, moisture retention and nutrient levels by digging in organic matter. Apply about two bucketfuls of well-rotted manure or garden compost every square metre/yard. Avoid using fresh manure.
Little fertiliser is required at planting. On average soil, apply a general-purpose fertiliser at a rate of 25g/1oz per square metre/yard. Where organic matter was not applied, double the amount of fertiliser. To reduce the need for weeding later, you could cover the soil with black plastic sheeting or weed-suppressing membrane, then plant the cloves through slits.
Carefully break up the bulbs into individual cloves or segments. Take care to plant them the right way up, with the flat basal plate facing downwards and the pointed end upwards.
Space the cloves 15cm (6in) apart, with the tip 2.5cm (1in) below the soil surface. In light soil, deeper planting can produce larger bulbs, but don’t plant deeply in heavy soil. Space rows 30cm (1ft) apart.
Prevent birds from pulling up newly planted cloves by covering with horticultural fleece until well rooted in.
Planting in modules
On heavy, wet soil, garlic is best started off in modules in autumn, overwintered in a coldframe or unheated greenhouse, then planted out in spring.
Partly fill a modular tray with multi-purpose or soil-based compost
Insert one clove into each module and cover with compost
Keep in a cool place – a well-ventilated coldframe is ideal – to provide protection from the harshest winter weather
Make sure the compost is moist but not wet
Plant out in spring, 15cm (6in) apart
Although garlic is usually trouble-free, it can be affected by similar pests and diseases as onions and leeks, including leek rust, onion white rot, allium leaf-mining fly and leek moth.
Unfavourable growing conditions may also lead to:
Cloves forming on the stem – this is usually due to adverse weather, such as fluctuating temperatures in spring. Called top sets, the cloves can be used in the normal way.
Flower stalks – hardneck garlic readily produces flower stalks, which should be removed as soon as they appear and can be used in stir-fries. Softneck garlic occasionally produces flower stalks as a result of adverse growing conditions, such as high temperatures or drought.
Split bulbs – the crop was harvested late.
Green cloves – usually due to shallow planting or late harvesting. They can be used as normal, but are unlikely to store well.
Onion white rot
A soil-borne fungus that can cause yellowing and wilting of the foliage above ground, while rotting the roots and invading the bulb beneath the soil. A white fluffy fungus appears on the base of the bulb and later becomes covered in small, round black structures.
There is no chemical cure for onion white rot when it is the soil. It is important to avoid introduction to previously clean sites. It is transported in contaminated soil, for example on tools or on muddy footwear. Take particular care in areas where cross contamination can occur easily, for example on allotments.
This is a fungal disease causing bright yellow spots on the leaves. It is often worse in long, wet spells.
Mild attacks of rust won’t harm the plant, but serious infections may cause leaves to shrivel and affect yield. There is no control for rust once you have the infection. Make sure you don’t crowd plants, as this increases humidity and increases the likelihood of infection. Dispose of any badly affected plant material, and don’t grow garlic, leeks or onions in the same spot for three years.
Birds, especially pigeons, can cause an array of problems including eating seedlings, buds, leaves, fruit and vegetables.
Protect the plants from birds by covering them with netting or fleece. Scarecrows and bird-scaring mechanisms work for a while, but the most reliable method of protection is to cover plants with horticultural fleece or mesh.
While the bulbs are still growing, you can harvest a few of the green leaves to use as a garnish or in salads. You may also find ‘top sets’ or garlic cloves form on the stalk (due to changeable weather in spring) – these can be used as you would normal garlic cloves.
Garlic bulbs are ready to harvest once the leaves have turned yellow. Autumn-planted garlic is ready in early summer and spring-planted from mid-summer to early autumn. Try not to delay harvesting, as the bulbs open up and store less well if lifted late.
Carefully dig up the bulbs with a fork. Handle them gently, as bruising also reduces their storage potential.
Dry them off thoroughly in a single layer in the sun – under a cloche or in a greenhouse is ideal. Ventilate well to avoid excessive heat (above 30°C/86°F). Alternatively, place in a dry, well-ventilated shed or similar environment.
Expect drying to take two to four weeks, depending on the weather. If you spot any mould, you can speed up drying using a fan heater, but this is not usually necessary.
Once the foliage is dry and rustling, cut off the stalk and store the bulbs in a cool, dry place at 5–10oC (41–50oF), where further drying will take place.
Garlic can usually be stored for several months.
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The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.