It seems just like yesterday when I was sowing my exhibition onions and leek seeds (though it was actually over the Christmas period!) and over the weekend I was busy planting them out in the veg patch.

I am growing three varieties of exhibition onion, grown for size and weight – Robinsons Mammoth improve, Kelsae and Ailsae. These onions grow to around 3kg so are quite a size.

I’m only growing one variety of leek, the Robinsons Mammoth Improved pot leek, which again grows to quite a large size. Onions and leeks are very similar, and both are alliums, but onions will be harvested in the autumn while leeks will grow on through the winter.

Both onions and leeks require fertile ground that holds moisture – remember, they are mainly made of water. Both are stem pants and it’s this swollen stem which we eat. In fact, onion and leek roots tend to be shallow growing, hence the need for regular watering in dry weather. If they do dry out, you will find them going to seed before they should. They are still edible, though onions will not store very well.

Before planting onions and leeks, apply and rake in an onion and leek fertilizer with an NPK of 6:5:7. Onion plants are planted directly into the ground at the same level as they have been grown – do take the time so the onion foliage is lined up the same way, as this will make weeding a bit easier.

For leeks, these are dibbled in, creating a hole that is larger than the plant and placing the young seedling to the bottom – don’t backfill with soil, simply fill the hole with water. As with onion seedlings, take time to line up the like foliage, and allow space between the rows to allow earthing-up around the leeks as they grow.

Both onions and leeks are better when they are hand-weeded rather than with a hoe because they are shallow-rooted and using a hoe can damage the root system, reducing the overall size of the onion. During the growing season, water during dry conditions and continue to feed (liquid feed is fine and is absorbed more quickly and can be applied during dry conditions). Use a balanced liquid feed and one that contains trace elements – on a visit to a garden centre you will see there are lots of liquid-based fertilisers available. I would also suggest using a liquid fertiliser with added seaweed.

Although it is late for sowing large exhibition onions and leeks, you can still buy young plants online for direct planting into the garden, but ideally it is time to directly sow onions and leeks for general kitchen use.

It’s at this time of the year that my ornamental onions are beginning to show colour as you can see from my photograph. Most are planted as you would for any spring-flowering bulb, basically planting twice the depth of the bulb and in small clumps. Once planted they will be around for many years to come and the clump will get larger over time with more blooms.

Ornamental onions – or flowering alliums – are a large flowering group, though generally have purple ball-shaped flowers in the late spring and early summer. However, some forms can flower earlier and later. Alliums can vary in height and flower heads can also be small to football sized. I grow mine in the borders where they push their stems through the foliage of the perennial border plants. The reason for this is that, like most plants which grow from a bulb, you need to leave time for the foliage to die back into the bulb for following year’s flowering. Anyone who grows daffodils and narcissus knows that dying foliage can look quite messy so growing flowering onions in my border means as they fade the plants smother and hide the dying foliage, making the border self-cleaning.

Flowering onions also make a good cut flower, whose heads can be sprayed with glitter or colourings. They are best placed in a cool room to get the most from the cut bloom.