The Hows And Whys Of Autumn Onions And Garlic

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A shortage of garlic means prices are likely to rise next year, so why not grow your own?

DRIP, DRIP, drip fell the raindrops last week, in what felt like one interminably long rainshower. It came as light drizzle, then heavy cloudbursts, followed by a grey, monotonous mizzle that made a mire of any vegetable plots. It also did for the annual autumn tidy- up in the OPW's walled kitchen garden, because despite OPW gardeners Meeda Downey and Brian Quinn's best intentions, a week of such watery weather made the task impossible.

"The ground is soaking", complained Brian as he and Meeda took shelter in the Kubota tractor from yet another heavy shower. "Even just walking on it, the soil is sticking in a thick layer onto the soles of our boots, which is always a bad sign. There's no point in us trying to dig, hoe or even hand-weed until things dry out a bit – we'd just do more harm than good."

So, while the OPW gardeners are forced indoors to continue negotiations with the rain gods, this week's Urban Farmer column takes a look at the "hows" and "whys" of growing autumn onions, autumn shallots and garlic – three crops never grown in the walled garden because of the OPW gardeners' ongoing battle to contain the spread of the dreaded onion white rot. Once present in any garden, this depressingly persistent fungal disease will attack all members of the Allium family, and is almost impossible to eradicate. But restricting the number and variety of allium crops grown in the walled garden throughout the year (including leeks, onions, shallots, chives, scallions and garlic) is one way the gardeners hope to curtail the disease. "Technically we shouldn't grow any members of the onion family for at least eight years if we want to get rid of the disease, but that's not realistic. So instead we're just growing the typical maincrops during the summer months and avoiding any of the overwintering crops", explains Meeda.

Thankfully, most other gardeners can still grow these allium crops with relative impunity, as long as good garden hygiene (no diseased sets) and careful crop rotation is practised. And while organised gardeners will already have theirs in the ground since late September or October, even now in early November there's still just about enough time to plant autumn onion sets for harvesting next summer (look out for varieties such as Senshyu, Snowball, Shakespeare, Radar, Electric, Bianco and Troy). November is also the perfect month for planting out hardy shallot sets (known as Allium oschaninii, or Eschalote Grise /Griselle) and garlic cloves (any of the hard-necked types). Just keep in mind the fact that a friable, free-draining soil is the most important prerequisite to their success, as is a fertile, weed-free, compost-enriched spot in full sun (no fresh manure).

If the idea of a free-draining spot in full sun seems laughably unlikely at the moment, cast your mind forward to next summer and the anticipated pleasure of harvesting early onions, shallots and your very own home-grown garlic. It was, after all, the idea of the latter that first inspired GIY founder Michael Kelly ( to begin growing his own vegetables, when he realised that the garlic sold in his local supermarket was being shipped all the way from China. What's more, garlic prices are expected to rise steeply next year, due to a worldwide shortage. And if you want to really impress your neighbours, try growing elephant garlic (Allium ampeloprasum), the giant, milder-tasting relative of the true garlic, with bulbs that reach the size of an adult's clenched fist.

The first step, before planting any of these crops, is to carefully sort through the sets/cloves, discarding any that are shrivelled, bruised or damaged, as well as any that already show signs of growth. Poor quality sets/cloves like these will never produce a crop of any size and may even bring disease (Brian and Meeda strongly suspect that this is exactly how onion white rot first found its way into the OPW's walled garden). For the same reason, only use sets/cloves that have been certified disease-free (don't be tempted, for example, to plant garlic bought in a supermarket).

Try to choose their planting position in the garden with care, remembering that these crops will be taking up space until early or mid-summer of next year. When deciding quantities, also keep in mind the fact that unlike the summer maincrop varieties, autumn onions don't store well. So only grow enough to fill that hungry 6-8 week gap of mid-summer, before the maincrop themselves are ready for harvesting. Autumn-planted shallots and garlic will keep far longer (up to six months), so grow as many of these as you need.

When it comes to planting, it pays to have a dibber, a tape measure, two small sticks and a good length of string ready, because if there's any crop that shows up the sloppy gardener (tut, tut), it's most members of the allium family – perhaps the only exceptions being the ornamental alliums and chives. For whatever reason, the rest beg for perfectly straight lines and an orderly planting style – not just for ease of maintenance (lines are much easier to hoe) but also because, somehow or other, a crooked row of onions or garlic always looks wrong.

Recommendations as regards spacing and planting depth vary wildly. For autumn onion sets, either plant in rows (4"/10cm between sets and 10-12"/25-30cm between rows) or in blocks (7-8"/18-20cm apart each way), root-end down (important for all bulbous plants) and at a depth where just the tip of the set appears above ground. For Eschalote grise, plant at a similar depth but approximately 9-10"/23-25cm apart – you can expect an average yield of 15/20 shallots per set. The advice from the award-winning website of The Garlic Farm ( is to plant the individual cloves of hard-necked garlic varieties such as Purple Heritage Moldovan, Lautrec Wight, Chesnok Wight Aquila Wight 6"/15cm apart, with 18"/45cm between rows and at a depth where the tip of the bulb is covered by about 1"/2.5cm of soil. For elephant garlic, the recommendations are almost exactly the same, but increase the spacing from 6"/15cm to 12"/30cm.

Remember also that both the true garlic and elephant garlic will grow well in pots, using a good quality compost and a pot at least 8"/20cm deep. Keep them well-watered and then leave them outdoors, as all garlic needs a lengthy period of cold to "bulb up".

Feed with a general fertiliser in March to encourage fat healthy bulbs, and you should be able to start harvesting by early next summer. Yes, next summer . . . it's a nice thing to keep in mind during the wintry days ahead.

The OPW's Victorian walled kitchen garden is in the grounds of the Phoenix Park Visitor Centre, beside the Phoenix Park Cafe and Ashtown Castle. The gardens are open daily from 10am to 4pm

  • Next week Urban Farmer looks at growing crops in polytunnels
  • Fionnuala Fallon is a garden designer and writer

WHAT TO: sow, plant and do now

Sow: (Outdoors) broad beans, hardy peas, field bean green manure (Under cover) some CCA leaves

Plant: (Outdoors) Garlic, autumn onion and shallot sets, rhubarb sets.

Do: Continue harvesting storing, clear, weed and manure beds, order fruit trees

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