24 Cloves of Elephant Garlic Planted Under Fleece Through a Winter Frost Spell

Twenty-four cloves at 20cm centres filled roughly one square metre of raised bed. That spacing was deliberate: a single elephant garlic clove can build a midsummer bulb of 150g to 400g given enough room, moisture and feed. The planting stock came from split bulbs, with individual cloves weighing 30g to 60g, and each clove went in flat-base down.

Garden compost had been worked into the bed the previous autumn, so the cloves dropped into settled soil that had already had months to firm up. Elephant garlic, Allium ampeloprasum, overwinters as a small clump of leaves. Several weeks below roughly 10C give the plant the vernalisation period it needs for proper bulb division, so winter cold belongs to the crop’s normal cycle.

A late spring frost on emerged leaves is a separate problem. The December or January frost that arrives while cloves are still making roots mainly tests the soil surface. If the ground lifts and slumps over several freeze-thaw cycles, a shallow clove can be pushed upward before it has anchored.

The planting record

The cloves were planted 5cm deep, measured from the soil surface to the top of the clove. The 20cm spacing left enough air and feeding space for large bulbs without crowding the square metre into a dense allium patch. After planting, the surface was firmed, watered through, and covered with 30gsm horticultural fleece.

Frost heave is the real winter risk

Once elephant garlic has rooted properly, hard frost seldom ruins it. The awkward window is the six to eight weeks after planting, when the clove may have swollen and started to wake but has not yet driven enough root into the soil to hold itself down.

Frost heave is a physical movement of the bed. Water in the top layer freezes, expands, and lifts the surface. When the soil thaws by midday, the surface settles unevenly. Repeated cycles can walk a clove upward until the tip or shoulder sits exposed.

That is the practical reason for the 5cm depth. The 2cm depth sometimes quoted for softneck garlic leaves less cover above the clove, and elephant garlic cloves are heavier pieces of planting material anyway. A 30g to 60g clove sitting close to the surface is easy for frost movement to disturb.

The fleece went on to steady the soil. A 30gsm sheet holds two to three degrees of warmth at the surface, and its real value is the way it moderates the sharp swing between a frozen night and a thawing morning. On the coldest morning of the spell, the soil beneath the fleece read about 3C higher than the exposed path beside it.

That difference mattered because the covered bed held a crust that could still be worked with a finger, while the path beside it was hard. The cloves underneath were not being forced through a frozen lid. They sat in a slower, steadier temperature band while root growth began below.

Solid polythene would have changed the risks. Horticultural fleece stays breathable, lets rain and watering pass through, and avoids the stagnant damp that can raise botrytis and rust pressure. It gives the soil a gentler ceiling while still letting the weather reach the bed.

Pegging made the fleece useful. Metal ground staples went in every 60cm along the edges, with bricks weighting the corners. An unpegged sheet catches one gust and ends up across an allotment, leaving the bed bare precisely when the forecast matters.

Water still has to move through the cover

A covered winter bed can dry at the surface if cold wind runs across it for days. Because the fleece is porous, rain still reached the cloves and extra watering did not mean lifting the whole sheet. Damp soil also carries temperature more gradually, softening the harsh surface movement that lifts cloves.

The target was moist, settled ground. Soggy soil around alliums invites trouble, and dry loose soil is poor at gripping a newly planted clove. The previous autumn’s garden compost helped the bed keep its structure without going fluffy.

Pigeons, leaf tips and the first green shoots

The quieter benefit of the fleece showed once the first leaf tips appeared. Wood pigeons will pick allium foliage in hard weather when other forage is buried or scarce. A clove stripped of its early leaves enters spring with less leaf area to feed the developing bulb.

The sheet kept pigeons off during the coldest weather. On milder days it came off so the leaves could harden in open air. Before each frost night it went back over the bed and was pegged down again.

That on-and-off handling also made inspection possible. Any clove nudged upward by heave could be spotted before it dried out. The fleece did not hide the planting; it made the bed easier to keep stable through the spell.

Cold, vernalisation and bulb division

Elephant garlic needs cold exposure before it divides properly into a large bulb. The vernalisation period of several weeks below roughly 10C is part of why autumn and early winter planting can work well. Skip that cold and the plant may grow strongly yet fail to split as expected by harvest time.

So the fleece is a narrow tool. It softens surface extremes while still leaving the crop in winter conditions. It is never meant to hold the cloves above the temperatures that trigger division.

Hardneck Music and softneck Solent Wight make useful comparisons because both are true garlic types, while elephant garlic sits with the bulbing leeks. The shared allium habits can tempt a grower into treating them identically. Elephant garlic’s larger cloves, bigger final bulbs and leek-like growth make the winter settling period especially important.

The expected summer bulb size, 150g to 400g from a single clove, depends on the plant building leaves early and keeping them. A clove that sits loose, dries at the shoulder, or gets stripped by pigeons loses time before spring growth accelerates. The fleece was there to protect that early establishment.

Removing the fleece without shocking the bed

The cover did not stay on continuously through every mild spell. Leaves grown under cover too long can turn soft when wind and bright cold return. Lifting the fleece on calmer days let the emerging foliage toughen while the bed still had protection ready for the next frost night.

The timing was simple: off when the weather eased, back on before a freezing night. That rhythm kept the plants exposed to real winter light and air without leaving them open during the freeze-thaw cycles most likely to move the cloves. Held with staples and bricks, the sheet went back in a few minutes and did not disturb the soil surface.

The bed itself told more than the thermometer. A hard-frozen path alongside a workable covered square metre meant the fleece was doing its job, and leaves standing upright after a mild day outside the cover showed they were hardening as they should.

What the roots are doing now

Above ground the fleece dealt with the visible problems: wind lift, pigeon damage and a hard surface crust. What the roots have actually done is out of sight. Whether they have gripped firmly enough to resist the next freeze-thaw cycle will only show when the bed is lifted or when a clove either stands its ground or works its way to the surface.