How To Grow Onion Shallot and Garlic

It's a good time to buy Onions from Marshalls

Guidance supplied by Marshalls  

Every kitchen should have fresh supply of Onions, Shallots and Garlic, adding intense flavours to a huge range of kitchen dishes. Growing them is a pleasure and simple to do. Follow these guidelines for your own harvest of these delicious and versatile vegetables. Planting sets and cloves will give you a great harvest but can be slow to establish and birds do like to pull at them to get to the earthworms below, that have been attracted by the explosion of microbial activity in the rootzone. Using pre-rooted sets and cloves gets the plants off to a quicker start, leading to larger and earlier crops. Plus a lot harder for the birds to pull them up too!

Prepare the soil: Onions, Shallots and garlic prefer an open, sunny site and light, free-draining soil. If you have heavy soil, dig a generous amount of grit and organic matter into the planting area to ensure better drainage. Avoid planting in very heavy or freshly manured soil. Onions are sensitive to acidity, so if you have acid soil add some Garden Lime to the area well before planting, or a Pre-planting Onion, Shallot and Garlic Fertiliser.

Planting: Both autumn and spring varieties can be planted straight outside into prepared soil. Loosen the soil and dig in some Pre-planting Fertiliser for added nutrients.

Plant onion and Shallots with the tips of the sets showing at the soil surface. Onions should be spaced 5-10cm (2-4in) apart with 25-30cm (10in to 1ft) between rows, and shallots 15-20cm (6-8in) with 30-45cm (1ft to 18in) between rows.

Garlic cloves should be planted so the tip of each clove is 2cm (1/2in) below the soil surface. We suggest leaving 15cm (6in) between individual cloves and 30cm (12in) between rows. Plant pre-rooted plugs deeper than the plug they are grown in.

Aftercare: During the growing season, water if the weather is dry and give an occasional feed with a general liquid fertiliser, and keep the area weed free. Keep the water going in especially towards harvest time, as the bulbs can almost double in size in the last 4-6 weeks before harvest.

You might not know, but hardneck garlic varieties may produce a curly flower stem (commonly known as a scape) and cutting this off can increase the bulb size. The scape has a fresh, garlicky flavour that is absolutely perfect for stir fries!

Harvesting: Onions and Shallots can be lifted fresh in summer as soon as they reach a useable size, however if you’re harvesting for storage we recommend waiting until the foliage bends over and dies down naturally before lifting.

When harvesting garlic, we’ve found that a good indication is when their foliage starts to turn yellow and wither. Use a fork to gently remove the bulbs from the ground.

To lift, you should ease your bulbs out of the ground and allow them to dry outside for a couple of weeks (if the weather is fine) or in a well-ventilated greenhouse or shed.

Storing: Onions, shallots and garlic are ready for storage when the skins are completely dry and papery. They should be kept in a light, cool and well-ventilated place. Onions can be braided into long bunches and hung up to improve length or harvest and look great too!

Pests and Diseases: Onions are prone to various fungus-borne diseases, so we recommend trying to rotate their growing position each year so you’re not planting in contaminated soil.

Here are some of the most common pests and diseases to look out for!

Rust disease – Rusty spots form on both sides of infected leaves and break open to release dusty, orange airborne spores. Severe attacks may cause the leaves to shrivel prematurely and will reduce vigour.

Unfortunately, there is no solution or cure to rust disease. We recommend keeping a close eye out for the signs and removing and destroying any infected plants to help it spreading.

Onion white rot – The leaves will start to turn yellow and wilt, which prevents the bulbs from forming properly. A good way to tell if the bulbs have been infected is they will have white, fuzzy spots.

We recommend watching out for rot and removing any infected bulbs from the area to prevent it spreading.

Onion fly – The leaves will start to wilt and turn yellow, preventing the bulbs from developing. Onion fly can affect garlic and leeks as well as onions. The larvae of onion fly live in the soil and eat the roots of the bulb, eventually burrowing into the bulb itself.

Protect your crops with Insect Netting. However, if you do have issues with onion fly, we recommend simply discarding any bulbs.

Onion downy mildew – The leaves will begin to turn yellow and die off from the tip downwards. In wet weather, white mould develops on dead parts often turning a darker colour later. Remove and destroy any affected bulbs.

Onion neck rot – This fungal disease can occur in storage. We have found that to avoid neck rot, you should water regularly and stop feeding in August, in addition to keeping your crops dry after harvesting.