WATERING AND FEEDING
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
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
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.
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.