Home-grown garlic offers a superior flavor, making cultivation worthwhile. Successfully growing this crop in a challenging climate like Iowa requires specific knowledge to navigate the cold winters and distinct seasons. The plant follows a long, nine-month cycle, from fall planting to summer harvest, which means timing and preparation are everything for a bountiful yield. Understanding the plant’s needs in Hardiness Zones 4 and 5 is the first step toward a successful harvest.
Selecting the Right Garlic for Iowa
Garlic is generally categorized into two main types: hardneck and softneck, with hardneck varieties being the overwhelming choice for Iowa gardeners. Hardneck garlic is significantly more cold-tolerant and best suited for Iowa’s severe winters. This type also produces a stiff, central flower stalk (scape), a characteristic absent in most softneck varieties.
The reason hardneck garlic thrives here relates to a process called vernalization, which is a required period of cold exposure to stimulate bulb division. The harsh Iowa winter provides the necessary six to eight weeks of temperatures below 40°F (4°C) that hardneck varieties need to form a head of multiple cloves, rather than a single, undivided bulb (known as a round). Suitable hardneck cultivars for this region include Porcelain, Rocambole, and Purple Stripe types, such as ‘Music,’ ‘German Extra Hardy,’ and ‘Russian Red.’
It is important to source planting stock from reputable garden centers or online suppliers, not from grocery stores. Most commercial garlic is a softneck type grown for warmer climates, and it may have been treated to prevent sprouting. Selecting the largest, healthiest cloves from certified seed garlic stock will give the best chance for producing large bulbs.
Timing and Soil Preparation
Planting must occur in the fall to allow the cloves to establish a robust root system before the ground freezes solid. For Iowa’s zones, this generally means planting from late September through October, aiming for about six weeks before the first hard freeze. Planting too early can cause the garlic to sprout and produce top growth, which can be damaged by cold temperatures, while planting too late will not allow sufficient root development.
Garlic requires a full sun location and well-draining soil, as cloves will rot if they sit in standing water. Heavy clay soils can result in misshapen bulbs, so incorporating organic matter, such as compost, is highly beneficial for improving drainage and structure. Since garlic is a heavy feeder, incorporate a balanced fertilizer, such as a 10-10-10 blend, into the soil before planting. Good soil preparation ensures a loose environment for the bulbs to expand and provides the necessary nutrients for growth the following spring.
The Planting Process and Winter Protection
Before planting, separate the bulb into individual cloves, ensuring the papery skin (wrapper) remains intact on each clove to prevent disease. Use only the largest outer cloves for planting, as these produce the biggest bulbs, saving the smaller inner cloves for cooking. Plant each clove with the pointed end facing up and the flat, basal plate side facing down, which is where the roots will emerge.
The ideal planting depth is generally two to three inches, which offers sufficient protection for the clove while allowing the new shoot to emerge easily. Space the cloves approximately six inches apart in all directions to give each plant enough room to form a large, healthy bulb. Planting cloves upside down or on their side will result in small or oddly shaped bulbs.
Immediately after planting, apply a heavy layer of winter mulch, which is necessary for successful overwintering in Iowa. A thick covering of four to six inches of weed-seed-free straw or shredded leaves acts as an insulator, moderating soil temperatures and protecting the cloves from damaging freeze-thaw cycles. This insulation prevents the cloves from being heaved out of the soil by frost action.
Spring Growth, Harvest, and Curing
As the soil begins to thaw in early spring, the garlic will break dormancy and begin to send up green shoots. At this time, it is beneficial to pull back the deepest part of the winter mulch slightly to allow the soil to warm faster and the shoots to emerge easily. Once the shoots are actively growing, apply a nitrogen-heavy fertilizer to support the rapid development of the foliage.
Hardneck varieties will produce a coiled flower stalk, or scape, typically in late spring or early summer. Removing this scape is an important step to redirect the plant’s energy toward bulb development underground, which maximizes the final bulb size. The scape should be cut off when it has formed one or two coils but before it straightens out completely.
The time for harvest typically arrives in July or early August, which is indicated by the foliage dying back. The bulbs are ready to be dug up when the lower third of the leaves have turned yellow or brown, leaving about four to five green leaves remaining on the plant. Digging the bulbs carefully with a garden fork is recommended to avoid bruising, which can shorten their storage life.
After harvesting, the bulbs must be cured to dry the outer wrappers and necks for long-term storage. Lay the unwashed bulbs in a shaded, dry, and well-ventilated area, such as a covered porch or a shed, for three to six weeks. Curing is completed when the wrappers feel papery-dry and the stems are completely brittle, after which the tops and roots can be trimmed, and the garlic can be stored for year-round use.