CARING FOR ONIONS IN RAISED BEDS AND CONTAINERS
The needs of onions grown in raised beds are simple. Never let the soil dry out, onions appreciate lots of water. They also appreciate being fed regularly especially when grown in raised beds. Competition from weeds is not good for any vegetable but this is especially the case with onions. Their foliage provides no soil protection to smother weeds.
WATERING AND FEEDING
In our raised bed calendar we suggest watering all vegetables as required and feeding weekly. For onions, if you can avoid watering and feeding them from the the last week of July onwards they will do better.
WHY DO ONIONS BOLT
If fed and watered regularly onions tend to look after themselves. The only problem you may encounter is that your onions may bolt. We give an explanation of why onions bolt below, however there is little you can do to prevent it other than using hate treated onions sets rather than onion seed.
You know your onion plant has bolted when it produces a thicker than normal foliage stem and very quickly it will produce seed head. the best thing to do is pinch off the seed head as soon as you notice it. The onion will still be edible except perhaps for the central part of the onion bulb. Unfortunately though a bolted onion will not store. Do not break off the main stem because rain water will will run down into the centre of the onion bulb and cause it to rot.
So, why do onions bolt? In the wild, onions are biennials, which means they normally take two seasons to grow from a seed to producing new seed. In the first year onion plants grow producing foliage, roots and the onion bulb which we eat. If left to over-winter the onion will spring back into life the next spring and then produce a seed head.
The triggers for an onion plant to produce seed are a warm summer the previous year, a cold winter and then a warming spring. However, onion plants can sometimes be fooled by unusual weather conditions.
In the first year, if the weather in July / August is unusually cool this can fool the onion plant into thinking it has gone through the first winter. When the weather returns to normal temperatures the onion assumes it has reached spring and that it is time to produce seed. Hey presto, the onion will bolt.
When the onion begins to produce seed the central part of the bulb becomes soft and gradually more and more inedible. It also becomes impossible to store the bolted onion bulb.
Other conditions can cause onions to bolt such as lack of water or a genetic defect in a particular plant. But in general, these conditions will only cause one or two plant to bolt, not the entire crop.
NEXT STEPS
Go straight to the next page about harvesting onions by clicking here or see below for more pages about growing onions in raised beds and containers.
When and how to harvest onions
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