Natural Garden

Windowsill Salad Garden: Growing Spring Onions

A useful recent addition to my windowsill salad garden have been onions that I grow for leaves. It is very easy and quick to do, and fresh organic onion leaves are an excellent garnish for soups and salads.

A windowsill vegetable garden is particularly wonderful in late autumn and winter. Fresh salad leaves are still available in the garden in October and November, but at 5 or 6pm, when one has finished work and starts thinking about dinner, it is already completely dark. At this time of the year a windowsill salad garden becomes truly enjoyable. Everything there looks fresh and beautiful, and is untouched by frost. Salads grown indoors are also easy to harvest, and require hardly any washing.

Windowsill salad is of course also a great idea for anyone living in a city, without a garden. And if you are growing a variety of microgreens on a windowsill, you can have a diverse vegetable garden in a tiny space.

How to grow spring onions on a windowsill

Onion leaves can be grown from bulbs bought in a shop or collected from the garden.

Preparing onion bulbs (optional)

This is an optional step, but could be useful for some. These techniques can be used by someone growing spring onions on a larger scale, for a restaurant, for example.

To speed up the growth of roots and leaves, bulbs can be soaked in warm water (30-36C) for about 12 hours. This will reduce the time necessary for the leaves to develop by about a quarter.

You could also cut off with a sharp knife the very top of the bulb, exposing think fleshy scales. This will speed up the emergence of leaves by 2-4 days. It is important not to cut too deep, however, because this will reduce the amount of nutrients available to leaves when they start growing. None of this, however, is essential.

Planting onion bulbs

Plant the onion bulbs in terracotta pots (plastic is best avoided!). Make sure that one third of a bulb is exposed above the soil.

Any soil is fine, because leaves will use primarily the nutrients stored in the bulb, as they develop. Ideally the soil should be loose and rich in organic matter. For example, the garden soil mixed with compost or leaf mold is great.

The pots can be small, only slightly wider than the bulbs and about 10-15cm deep. This will give enough space for roots to develop.

When planting leave on top about 2cm free of soil for watering.

Onion bulbs planted in pots for growing in a windowsill salad garden.
Onion bulbs planted in ceramic pots, 10 October.

Exposure to cold (optional)

This is another optional step that helps roots to develop faster.

Once the bulbs have been planted, water them, and ideally keep them at a temperature 5-12C for 5-6 days for roots to develop. A higher temperature slows down the development of roots.

Since in many places this is the normal outside temperature in mid-autumn, the pots can be simply left in the garden for a week.

Growing onion leaves in a windowsill salad garden

Following an exposure to cold, onion bulbs can be brought to a bright windowsill in a warm room. The best temperature for a fast growth of leaves is 20-25C.

Onions grown in this way are not particularly sensitive to light and develop well even when days are short.

The leaves evaporate a lot of water and can dry out easily. So it is important to keep watering the pots.

The leaves will soon emerge and continue growing. When some are cut, new leaves will develop.

Spring onions grown in a windowsill salad garden.
Spring onions 16 days after planting, 26 October

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