Pre-chill garlic cloves before indoor growing

By Kratky Garlic ·

Garlic bulbs and loose cloves on a wooden table, ready to pre-chill before planting

If you want an indoor garlic plant to make a real, divided bulb, pre-chill garlic cloves before you plant them. Without a cold spell, most garlic grows leaves happily and then forms a single round bulb, or none. This is the step most indoor growers skip.

Why garlic needs cold

Garlic evolved with winters. Oregon State University describes a cold requirement, called vernalization, of about six to eight weeks at average temperatures below 40°F, with some strains needing less. Only after that does the plant respond to lengthening days by forming a bulb with cloves. Research on clove chilling has found that chilling the cloves before planting can satisfy that requirement, so the plant does not need cold while it grows.

How to pre-chill garlic cloves

  1. Start with whole bulbs. Leave the bulbs whole until you are ready to plant; separated cloves dry out faster.
  2. Bag them loosely. A paper bag or mesh bag lets moisture escape. Sealed plastic invites mold.
  3. Refrigerate for six to eight weeks. A refrigerator usually runs between about 35 and 40°F. Keep the garlic away from fruit such as apples, which give off ethylene.
  4. Plant straight from the fridge. Break the bulb into cloves, keep the skins on, and set them in net cups. Follow the Kratky garlic setup.
A single garlic clove in its papery skin, with the flat root plate at its base
Keep bulbs whole in the fridge; a loose clove dries out faster.

Do not overdo it

More is not better. Oregon State reports that cloves held for long periods below 40°F can produce rough bulbs, side shoots and early maturity, and that cloves sprout fastest when stored at 40 to 50°F. Chill for the six to eight weeks you need, then plant.

Hardneck or softneck?

Hardneck garlic generally needs a longer, colder treatment than softneck. Hydroponic growers often start with softneck for that reason. See garlic varieties for hydroponics.

After planting, keep it cool enough

The cold treatment can be undone. Oregon State notes that temperatures above 85°F or water stress can reverse vernalization. Keep your container out of hot sun and never let it run dry. The rest of the plan, from leafing out to curing, is in growing garlic bulbs hydroponically.

Sources

  • Oregon State University, Oregon Vegetables: Garlic.
  • Scientia Horticulturae: “Growth, bolting and yield of garlic (Allium sativum L.) in response to clove chilling treatment”.