I’ve lost my onions, they’re Bolting!

A dissection of an Onion seed head
A dissected Onion seed head

There are signs of stress in the veg garden

Growing onions and plant care

It hasn’t been the best summer for plants here in Essex. Great for working on the tan, but incredibly dry if you have a veg plot or an allotment.
Unfortunately, as a new gardener I hadn’t the seasonal experience to respond in good time to the extreme weather. Meanwhile, my onions began to grow a very tall central stem instead of a big round onion at it’s base. They had, I was soon to discover, begun to bolt.

Why do Onions Bolt?

Bolting is a term used to describe a plant developing a premature flowering stem. The purpose of which is to produce seeds and so reproduce. Bolting happens as a response to deteriorating growing conditions, such as drought or lack of minerals in the soil. In other words adequate watering and feeding is essential. Something I wrote about earlier in ‘You reap what you sow’ so I had no excuse at all for allowing this to happen.
I’ve also read that bolting can also be induced due to a change in daylight hours. For example, plants expecting longer hours of sunlight getting less will begin to bolt and want to go to seed early. It would be interesting to see what would happen if I sowed some onion sets well out of season, perhaps it would be a way to just produce a plant with a seed head to store for next year. I’ll put that to one side as an experiment to try out later in the year, you’ll have to subscribe and stay in touch to find out how I get on. But for now I’d like to just pass on my research so that you don’t have to watch your onions reach for the sky.

Close up of an onion seed head before opening
A dissection of an Onion seed head

How to prevent onions from bolting

Essentially my onions wanted to put out seeds early because they was in trouble and knew they wouldn’t reach their natural lifespan, so made a dash to reproduce. This was an accelerated natural reaction to the stressful environment it was trying to grow in. It is therefore the gardener’s job, as guardian of their pot to be mindful of extended periods of unusual weather, especially in this time of global warming and climate change. Odd things are happening to our seasons and weather patterns. We also need to pay more attention to the effect this has on the soil and it’s propensity to supply natural minerals to the roots of our fruit and veg. Without water, the soil dries and can not dilute minerals within it.

Red Onion bulb growing in the ground

The two main causes and remedies for preventing plants from bolting are …

1/ It’s too dry.

We’ve had quite a dry spell in the UK this summer and I haven’t compensated enough in my watering schedule to prevent some of my onions from suffering dehydration.

2/ Poor soil

As the root system of an onion is quite shallow it’s good practice to ensure well rotted organic matter, which will be full of nutrients, is in the top layer of your chosen plot. For no-dig enthusiasts I would highly recommend checking out how to build up your beds with guidance from Charles Dowding 
If your soil is suffering the best organic fertiliser to use for onions would be dried poultry manure pellets. 

Other crops prone to bolting

Brassicas such as cabbage, turnip & sprouts to name just a few, lettuce and spinach will soon react to changing conditions, as would beetroot. In our garden onions, beetroot, radishes and spinach all bolted this summer.

On A Plus, Nothing Goes To Waste

There are a couple of onions I am letting to go to seed fully in order to harvest the seeds. Some of these will be planted in a box to encourage onion sprouts as a very cheap substitute for spring onions, there’s a fairly good guid on growing sprouts here. 

Some of the other onions have been harvested for salads.

The bulb, although not fully grown is still fairly sweet and the leaves were chopped as you would chives. I didn’t use the thicker stem but nothing I have read suggests I couldn’t. As it’s texture is a little like a hollow celery stick, I’d be inclined to add it to stews or soups rather than chopped for a salad.

Of course any recipe requiring onions such as soups, quiche or omelettes for example would also have benefited from an early onion harvest, and the space left in the garden is soon occupied by spinach or chard, a favourite easy grower in the organic Greener Life UK garden.

Your questions, stories and thoughts on bolting veg are more than welcome. I am by no means an expert and would also love to hear your tips and advice on the matter. Especially as I am compiling a page all about the different varieties of onions and how to grow them.

Have you any idea how many varieties there are?

About Keep It Green 12 Articles
A passionate organic gardener and advocate of green living ideas and ethics being taught in mainstream education. A blogger, photographer & website designer. A food lover and believer that quality and smart healthy eating doesn't have to cost the Earth. Always learning, always searching.

2 Comments

  1. An interesting read, Roger.
    Onions take a long time, and a lot of valuable space, so I decided to grow spring onions instead this year, planting a few seeds every few weeks so that they keep me going with ‘onionyness’ through to the autumn.
    They can’t be stored, of course, and don’t have those deep, rich onion favours, but in small raised beds they take up less room and are quick to get a harvest (without that long exposure to possible weather, pest and disease). They are also more useful in quick summer recipes.
    A good beginners crop for those who want to start with something easier.

    • Thanks Judy, brilliant idea! I grow pea shoots in the same way. It’s been great harvesting our own salads this year, so rewarding and saved a fair few few quid as well I reckon. I shall be putting your suggestion into practice 💚🌱🌱👨‍🌾🥗

Please leave a comment and sign up for more updates