Our basic guide to growing onions from Seeds or Sets
Soil preparation,
Onions like a well drained site to grow at their best but even the most heavy soils can be improved enough by adding organic matter, grit or compost. If you do have heavy soil it may be worth considering planting on ridges to improve drainage.
Onions prefer neutral or slightly alkali soil so it’s worth testing. If soil the soil is acid I would recommend added lime or calcified seaweed to bring acidity down. PH 6.4 to 6.8 is ideal.
To grow from Seed,
Growing onions from seed is much more difficult than growing from Sets but it has a number of advantages. Firstly there are far more varieties available to choose from. If your looking to grow show onions or very large onions you should almost certainly choose this method as the record holders such as Alisa Craig, Unwins exhibition and Kelsae are usually only available as seed.
Sow seeds indoors or in a greenhouse at 10-15 Celsius, between January and March. I use 12 unit modular trays and sow about 3-5 seeds per module. If your looking for large onions it pays to plant earlier and if growing for size some people plant in December! If you are looking to grow without artificial heat or light i would recommend planting seeds at the end of February at the earliest.
When you onions have two leaves and are starting to look more sturdy and about 6″ tall it’s time to pot on or plant out.
Carefully separate the plants and plant out early spring for harvesting in August.
Growing from sets,
Growing from sets is much easier method,
For best results prepare soil a few months before Sets are planted. To prepare add well rotted manure and check the acidity. Add calcified seaweed or lime if required.
Sets should be planted out in early March. There is much debate as to whether to plant before or after the last seasons frosts. In my experience planting earlier than this has not improved the crop.
For large consistent onions, Plant onions 6″ (15cm) apart in rows 20cm apart. If limited with space you may be able to increase productivity by growing more smaller onions by planting 10cm apart in rows 15cm apart. For larger varieties such as Kelsae or other large exhibition bulbs you will need to plant further apart.
Sets should be planted 2-2.5 cm deep so that the tips are just under the surface.
Growing,
Onions are pretty maintenance free when it come to growing but liberal watering and careful weeding will ensure you get a good crop.
Harvesting and Storage,
Onions are ready for harvesting a week or two after the foliage has gone yellow and brown. On a sunny day carefully lift the onions with a fork talking care not to bruise them. Place in a sunny and dry location for about a week so that the outside of the onions can dry off completely. Once dry store in a cool dry place. I use a cardboard box full of straw and put it in the shed, Onions stored this way can last upwards of 3 months. When raiding your onion store, do check for signs of rot because once started this can quickly spread to the whole box.
Looking forward to reading your comments.
Doug
