Garlic is a rewarding crop, but successful cultivation in Minnesota requires specific knowledge due to the state’s extreme winter climate and short growing season. Garlic must be planted in the fall to ensure proper development. This timing allows the clove to establish a strong root system before the ground freezes, which is necessary for bulb formation the following summer. The cold period, known as vernalization, is required for many varieties to divide into cloves instead of forming a single, round bulb.
Selecting the Right Garlic for Cold Climates
Choosing the correct type of garlic is the most significant factor for survival in a Minnesota winter. Garlic is categorized into hardneck and softneck types, but only hardneck garlic is reliably winter hardy enough for northern regions. Hardneck varieties produce a stiff central flower stalk, or scape, and yield bulbs with fewer but larger cloves, typically four to twelve per bulb. These varieties withstand the prolonged cold temperatures characteristic of Minnesota winters.
Ideal hardneck varieties for this region include Rocambole, Porcelain, and Purple Stripe groups. Specific types like ‘Music’ (Porcelain), ‘Chesnok Red’ (Purple Stripe), and ‘Spanish Roja’ (Rocambole) perform well in cold climates. Source healthy, disease-free “seed garlic” from local growers or reputable suppliers. Grocery store garlic is usually a softneck variety not adapted to cold climates and is not recommended.
Timing and Preparing the Planting Site
Planting time is calculated to allow for root development without encouraging excessive leaf growth before the deep freeze. The optimal planting window generally begins one to two weeks after the first killing frost, extending from late September through October. Northern regions should aim for the third or fourth week of September, while southern areas, including the Twin Cities, can wait until the first or second week of October. The goal is for cloves to develop roots and a small shoot that remains below the soil line before the ground freezes solid.
Garlic demands full sun and excellent drainage to prevent rot. Before planting, prepare the site by tilling the soil to a loose depth to allow for proper bulb expansion. For the heavy clay soils common in Minnesota, incorporating organic matter improves both drainage and fertility. Adding several inches of well-rotted manure, compost, or peat moss helps create the loose, moisture-retentive texture that garlic prefers. Garlic grows best in a slightly acidic to neutral soil pH range, ideally between 6.0 and 7.0.
Step-by-Step Planting and Winterizing
Planting begins by carefully separating the bulbs into individual cloves one or two days beforehand. Select only the largest and healthiest cloves, ensuring the papery outer skin remains intact. Cloves are planted with the flat, root-end facing down and the pointed tip oriented upward. Planting upside down causes the shoot to curve, resulting in a misshapen and smaller bulb.
The correct planting depth is two to three inches from the base of the clove to the soil surface. Deeper planting provides greater winter protection and extends root growth time before the soil freezes. Cloves should be spaced approximately six inches apart within the row. After planting, rows must be covered with a thick layer of mulch for winterizing.
Mulching immediately helps moderate soil temperatures and prevents freeze-thaw cycles that can heave the cloves out of the ground. For Minnesota’s deep-freeze conditions (USDA Zones 3-4), a minimum of four to six inches of clean, weed seed-free straw is required. In the coldest regions, increasing this depth to six to eight inches provides maximum insulation. Shredded leaves or chopped corn stalks can also be used to protect the cloves until spring.
Spring Care and Harvesting
When temperatures warm in early spring, the shoots of the overwintered garlic will emerge. Gardeners should remove the heavy insulating layer of mulch once the threat of extreme cold has passed, typically leaving a lighter layer of one to two inches. Removing the bulk of the mulch allows the soil to warm more quickly, encouraging spring growth. A thin layer helps preserve moisture and suppress weeds. Garlic has a shallow root system and requires consistent moisture, needing about one inch of water per week during the spring growing season.
In early summer, hardneck varieties develop a coiled flower stalk known as a scape, which must be removed to maximize bulb size. If the scape remains, the plant directs energy toward forming bulbils, resulting in a smaller underground bulb. Scapes should be snapped or cut off just after they have formed one or two curls, before they straighten and become woody. This removal redirects the plant’s energy back into the bulb, potentially increasing its final size by 20% to 30%.
Harvesting typically occurs in Minnesota between late June and late July, about three to four weeks after scape removal. The correct time to harvest is indicated by the plant’s foliage: the lower leaves should be brown and dried, but at least half of the upper leaves must remain green. Harvesting too early results in immature bulbs that shrink when cured, while harvesting too late causes the cloves to separate, compromising storage life. The bulbs should be carefully dug with the shoots and roots attached, and then placed in a warm, dry, and airy location to cure for three to four weeks.