Above are two photos of our winter onions growing happily in our allotment field. These were planted at the start of October and have done well so far, even avoiding the birds pulling them up!! There are 100 planted so far with more to come, but how any do I need?

These onions will overwinter, with the growing slowing down and stopping as Winter takes hold – then burst into life next Spring to be ready for harvesting at around June time. By that time the Spring sown onions should be established and be growing towards a harvest time of August/September.

But are these enough to support us? Lets get mathematical….

If you want 7 Onions each week it would logically follow that you need to plant 7 Onions, each week, all year. Allowing for an initial 20 week lead time for growing. Onions should be popping off the growing conveyor belt each week, problem solved. Well no.

Lets just start with how many to grow to get 7 onions each week. We can calculate it fairly easily. If we calculate the weekly requirement by how long they take to grow this will give us how many we need to have growing at once (7 x 20 = 140). If we then take that total and multiply it by how much space each Onion requires it will give us the length of row we need to plan for ( 140 x 5″ = 700″ (or 58′)).

So we plant 140 Onions and every week we pull up 7 to eat, and plant 7 more, and our 58′ row goes for ever on.

However, as mentioned earlier, Onions will not grow at an even pace all year indeed they will stop growing during the Winter months. We need to tweak the calculation to take this into account and consider harvesting onions to store for use. Thus the algorithm comes out like this:

Live grow (what you require each week x growing span each year) + Storage grow (what you require each week x non-growing span in year) = self sufficiency.

So do we have enough Onions? I’ll take this line of thought further in future posts.

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