Gadenin日本語Get the appCold is what the crop needs, so do not protect it too well
Garlic requires several weeks below about 40F (4C) at the clove before it will divide into separate cloves in spring. A bulb that never gets that cold period grows as a single undivided round, sometimes called a solo bulb, which is edible but is not what you planted for. So the aim over winter is not to keep the plant warm, it is to keep it stable.
Hardy garlic survives to around minus 20F (minus 30C) under snow or mulch, and the leaves themselves will die back to the ground without any harm to the bulb below. Yellow or browned leaf tips in midwinter are normal and need no action. What actually damages the crop is the ground repeatedly freezing and thawing, and standing water.
Mulch three to four inches deep after the first hard frost
Wait until the top inch of soil has frozen once, then lay straw, shredded leaves or grass clippings three to four inches (8 to 10 cm) deep over the row. Mulching before the ground has cooled traps warmth, keeps the plant growing when it should be slowing, and gives mice somewhere comfortable to sit and eat your cloves.
The point of the mulch is to hold the soil temperature steady rather than to keep it warm. Bare soil in a cold garden freezes at night and thaws in the sun, and each cycle lifts the clove a little further out of the ground until the roots snap. Under mulch the soil stays frozen through the day and the clove stays put.
| Mulch material | Depth | Notes |
|---|---|---|
| Straw | 4 inches (10 cm) | The best insulator. Shake it loose so it does not mat |
| Shredded leaves | 3 inches (8 cm) | Free and effective. Whole leaves pack down and shed water |
| Grass clippings | 2 inches (5 cm) | Apply thin and dry. Thick green clippings heat up and rot |
| Bark or wood chip | 2 inches (5 cm) | Slow to break down. Hard to pull back off in spring |
Frost heave is the one thing that will cost you plants
Frost heave is the soil expanding as it freezes and physically pushing the clove upwards. You find the clove sitting half out of the ground with a white root fan exposed to the air, and once those roots dry the plant either dies or limps through spring making a bulb a quarter of the size it should be.
Walk the bed after any spell where the ground froze hard and then thawed. Any clove that has risen should be pushed back down straight away, before the exposed roots dry out. Do it on a day when the soil has thawed enough to give, and never force a clove back into frozen ground because you will tear the basal plate off.
- Check after every freeze and thaw Look along the row for pale shoots standing proud of the surface, or for a clove visible at the top of a small crater. Both mean heave.
- Push it back and cover it Press the clove down until the tip is two inches (5 cm) under, then draw soil over it and firm gently. Add mulch on top so it does not happen again.
- Do not lift and replant Digging up a heaved clove and putting it back in a fresh hole breaks far more roots than pushing it down does. Push, do not lift.
Frost heave hits shallow-planted cloves almost exclusively. If you lose plants to it two winters running, plant an inch (2.5 cm) deeper next autumn rather than mulching more heavily.
Do not water and do not feed until spring
A dormant garlic plant uses almost no water, and winter rain or snowmelt is normally more than it needs. Watering a cold, wet bed is how basal plate rot starts, and once the plate rots the bulb is gone with no warning above ground until spring. In an unusually dry, snowless winter, water once a month and only enough to damp the top two inches (5 cm).
Feeding in winter is worse than useless. Nitrogen applied to a cold soil either leaches away with the rain or pushes soft leaf growth that then gets frozen. Everything you worked into the bed at planting is enough to carry the plant to spring, and the first feed belongs to the moment new leaves start moving.
| Winter condition | Action | Reason |
|---|---|---|
| Snow cover on the bed | Nothing at all | Snow is the best insulator there is. Leave it |
| Repeated freeze and thaw, no snow | Check for heave, add mulch | Cloves lift out and the roots dry |
| Standing water after rain | Cut a drainage channel off the bed | Waterlogging rots the basal plate |
| Dry, mild, no snow | One light watering per month | Roots keep growing slowly whenever soil is above freezing |
| Leaf tips yellow and dying back | Nothing | Normal winter dieback. The bulb is unaffected |
Mice, birds and what to check on a winter walk
A thick straw mulch is warm, dry cover, and mice will move in and eat cloves from underneath, leaving the mulch above looking untouched. Birds pull at green shoots poking through the mulch, particularly in a hard winter when little else is available. Neither problem is visible unless you go and look.
Once a month, pull back the mulch in two or three spots along the row and look at the soil surface. You want to see intact shoot tips and no runs or droppings. Note the date of each check and anything you find, because a garlic bed gives you almost no other feedback between autumn and spring, and next year those notes tell you whether your mulch depth and your planting date were right.
- Lift the mulch in a few places Check two or three points along the row. Look for tunnels at soil level, chewed clove skins and droppings, which all mean mice.
- Thin the mulch if you find runs Pull the straw back to two inches (5 cm) so the cover is less attractive, and set traps at the edge of the bed rather than in it.
- Net exposed shoots against birds Where green tips are showing through in a hard winter, lay netting over the row on short canes. Pull it off as soon as growth restarts.
- Log every check Write the date, the weather, whether shoots were showing, and any damage. Three or four winter entries make next year's timing decisions obvious.