Mulching Onions

The time has come to mulch my onions.  Mulching accomplishes at least two things:  It keeps the roots more evenly moist and discourages weeds. My main season winter storage onions are up beyond 18 inches tall and the weather prediction is for extended warm and dry.  I just did my second weeding by hand and so this is also a good time to cover the soil up for weed suppression.

I don’t like to mulch my onions any earlier than now since it cools the soil and might slow the growth during our cool, wet spring.

One old book I had, classified onions as Light Feeders along with carrots, peppers, parsnips, peas and beans.  I don’t quite agree.  I think onions were classed as lighter feeders because their root balls are quite restricted and don’t reach far out like other vegetables.  But they really do need a rich soil if grown at optimum spacing.

Because of their less-extended root system, they are more susceptible to the drying out of the soil (especially my sandy soil) during dry periods, so an even moisture environment is superior and a mulch helps accomplish that.

Before mulching

My onions are grown in rows across the bed.  The rows are one foot apart and the onions are 8 inches apart within the rows.  That gives 96 square inches per plant.  (Actually I seeded indoors in January, two seeds per pot so many 'plants' are pairs of onions.  Pairs give me slightly smaller onions which isn't a bad thing since mine tend to be so big.)  About the same spacing could be accomplished with 10 inch equidistant spacings but there’s a reason for my wider spaced rows. 

Several years ago, my son TOG had invited volunteers to help hand weed his onion beds as he was falling behind and could lose the crop.  One of the free helpers was a bit rough and heavy handed.  He had a tendency to reach in and often break the taller onion leaves while going after the lower growing weeds.  After a couple of weeks of cooler weather, some virus, fungus or disease whooshed though the beds with the broken leaves and wiped out the crop.

That is why I like my onion rows running across my four foot wide bed with enough space to reach in from the side without breaking any leaves for weeding and mulching.  TOG's multiple rows run down the length of his 30 inch wide beds and once the onions are tall it gets difficult to reach in over a row to get at the weeds by hand.

My mulch of choice is autumn leaves from a neighbour’s maple tree.  This year I used some that I’d stored in a barrel for over two years.  Last year I used 7 month old leaves and first chopped them up with the lawn mower.  Unfortunately, mowing reduced the volume to a quarter of what I’d started with, the mulch was too thin and I quickly ran short.  So this year I just crumpled and broke the very old leaves with my hands before spreading them 1.5 to 2 inches thick over all of the bed.  And I was careful not to damage any onion leaves.  It worked well.

I did the same for my garlic.  

Any weeds that do make it through the mulch are grabbed by reaching in between the rows at ground level.  The sunshine and soil fauna will break the leaf mulch down over the next two months and even though much of it will be gone by harvest time, about the end of July, I really believe mulching onions makes a big difference.

Happy Gardening.