Onions, Spring onions & Chives

Onions

Onions are easy to grow from sets (immature onion bulbs) which are widely available.

In 2020, I took part in a “mulch for onions” experiment run by Garden Organic http://www.gardenorganic.org.uk. They wanted to try out alternatives to the commonly used woven plastic (weed fabric) mulch. Although the weed fabric can be reused for several years, there are issues of plastic fibres / microplastics being deposited in the soil.

The mulches in the experiment were:

• no mulch
• weed fabric
• paper
• biodegradable starch
• home-made mulch – I used bark chippings, but other participants used grass clippings, compost or reused cardboard.

Each patch was 0.09m² planted with 10 onion sets at the end of March. I had a few spare onion sets so I planted them under bark mulch too. The thick bark mulch delayed emergency of the onions and the “no mulch” section definitely had more weeds!

Unfortunately in July the onions were damaged – possibly something wild got into the space. If they hadn’t been damaged, they would probably have developed a bit more over the following few weeks. By early August, the leaves had withered and the onions were harvested.

From my own results (table below), the biggest harvest was from the section covered with weed fabric, but “no mulch” was only slightly lower and had the advantage of not harbouring slugs! The other mulches may have caught up later in the season if the plants hadn’t been damaged by July. Although all the mulches reduced the number of weeds in the patch, generally they didn’t stop weeds very close to the onions, as these peeked through the growth hole. Weeds so close to the onion had to be pulled by hand as using a hoe or knife could easily damage the plant. I found the biodegradable starch mulch was quite difficult to lay over the plot as the slightest breeze disturbed it.

Garden Organic published the experiment findings from 72 participants across the UK in “The Organic Way – autumn/winter” on p28 (in case you can get your hands on a copy!). The highlight are:

• Natural mulches (eg compost, grass clippings, woody waste) and reused cardboard had a lower environmental impact than any of the purchased mulches.
• Loose mulches (eg bark chips, grass clippings) did not reduce the weed cover as much as other types
• Mulches are not effective against bindweed as it can send tendrils through the growth holes while the roots are protected by the mulch
• Generally, mulches increased the onion size by 12-13%
• Mulches increase slug numbers slightly – this might have been more obvious in a wetter summer
• Paper mulch was easy to lay over the plot and was starting to breakdown by harvest time. However, it was also quite expensive (similar to the weed fabric which could be reused for several years)
• Biodegradable starch takes longer to break down than the paper (manufacturer estimate is 36 months) but would not be usable for a second season. There is a lack of knowledge about the impact of the biodegradable starch on the soil as it breaks down.

My choice for onion sets in the future is likely to be “no mulch” as slugs and bindweed tend to be problems in my garden and I try to avoid anything which gives them an advantage! Having enjoyed onions from sets for several years, the next challenge will be to try them from seed!

Spring Onions

If you don’t have space for bulb onions, it’s worth considering spring onions! These can be easily grown in containers, harvested in a short time and the entire plant is edible – even the roots! Although I do throw away the heel of the bulb and the top of the roots because it’s practically impossible to clean all the soil out.

A major advantage of spring onions is that they can be grown throughout the year! Sowing from October to February is possible with a bit of protection (eg indoors or in a greenhouse). In 2020, I sowed seeds into individual pots in the greenhouse in August and harvested some as early as November and some as late as January 2021.

Last year I sowed seeds in April and bought some little plants in May 2021 (I like to have a good supply!). The plants were well established when I started harvesting in July and they’ve lasted all the way through a mild winter!

As well as space saving, another reason for growing spring onions is to avoid the elastic band and little plastic tag that you buy at the same time!

Chives

if you’re looking for the ultimate ‘easy’ crop – try chives! Buy a little pot from a garden centre or nursery – you’re less likely to have long-term success with the pots sold in supermarkets. Give them more root space by moving to a bigger pot (at least 15cm diameter and 10cm deep) or plant them in the garden – bear in mind they’ll have pretty flowers too, so you don’t have to hide them!

I’ve got pots of ordinary chives and also chinese chives – between these I can avoid buying chives apart from in deepest winter. The harvest will always be tiny, but chives are much more expensive to buy than onions or spring onions (see table below). You can also avoid bringing home the plastic envelope they’re usually wrapped in! If you fancy, you can eat the flowers but I prefer to leave them for the pollinators!

Space efficiency / Value for money

Crop	Year	Soil area (m2)	Soil Depth (m)	Annual Harvest (kg)	Mass Yield (kg/m2.d)	£ yield (£/m2.d)	Calorie space* (m2)	Protein space* (m2)
Onion – no mulch	2020	0.09	0.15	0.97	0.0695	0.06	156	123
Onion – weed fabric	2020	0.09	0.15	1.032	0.0740	0.06	146	115
Onion – paper mulch	2020	0.09	0.15	0.696	0.0499	0.04	217	171
Onion – biodegradable starch	2020	0.09	0.15	0.69	0.0495	0.04	219	172
Onion – bark mulch	2020	0.09	0.15	0.615	0.0441	0.04	246	194
Spring onion	2021	0.1782	0.15	0.149	0.0139	0.05	2711	1206
Chives	2021	0.12	0.2	0.01	0.0002	0.35	29229	6577