Although garlic (Allium sativum) is winter-hardy in U.S. Department of Agriculture hardiness zones 3 to 8, it's usually grown by home gardeners as an annual, its mature bulbs harvested after a single growing season. In Ohio, garlic should be planted in the fall or early spring so that it has plenty of time to develop before the end of summer.
Choosing a Variety
Garlic can be of either the soft-neck or hard-neck type. Soft neck garlic varieties often have larger bulbs and will store longer than hard-neck types, but hard-neck varieties tend to be more cold-hardy and are better suited to the climate in Ohio. Varieties that do well in the state include "Music," "German White" and "German Red."
Timing of Planting
Garlic plants put their energy into leaf development when the weather is cool, and once the days start to get warmer, leaf growth stops and bulb growth takes over. Consequently, the plants need plenty of time early in the growing season to develop enough foliage to fuel bulb development later.
Most of Ohio falls into USDA zone 6a; exceptions include areas along the Lake Erie shore and the southern part of the state, which are classified as USDA zone 6b. Other higher-elevation areas fall into USDA zone 5b. In these zones, planting cloves in the fall, starting in the third week of October, will give the plants a jump on the season and allow the leaves to start growing through the winter. Alternatively, you can plant cloves in the early spring, but planting later than March or early April in Ohio will not give the plants enough time to develop fully.
Garlic needs a location that gets full sun through much of the day. It also needs well-drained soil with a light enough texture to allow for good bulb development. A loose, crumbly loam will satisfy both of the those requirements. Heavy clay soils, however, may retain too much moisture and cause bulbs to rot, and dense soils may result in small or ill-formed bulbs. Raised beds will also help soil to drain better and prevent bulb rot.
Garlic plants are heavy feeders, and they benefit from substantial amendment of the soil when they're planted. Add organic compost to the planting bed both to increase the soil's organic content and to improve the soil's texture. Till 3 to 6 inches of organic compost into the top 12 inches of soil. In addition, add about 3 pounds of a balanced 10-10-10 fertilizer per 100 square feet of bed and work into the area prior to planting.
Clove Selection and Planting
It's best to buy seed garlic from a seed supplier or local grower. Supermarket garlic might grow in your garden, but when you know precisely what variety you're getting from a supplier, you're more likely to find a variety that will do well in your location.
Separate bulbs into individual cloves just prior to planting, taking care to leave the papery skin of the cloves intact. Choose the largest undamaged cloves to plant. Plant them with their tips facing upward between 1 and 1 1/2 inches deep; space the cloves 3 to 5 inches apart, and space rows of cloves 18 to 30 inches apart. Water the planting site until the soil is thoroughly moistened.
Garlic doesn't need much water after planting, but if the soil is dry and it's not likely to rain soon, water the newly planted cloves thoroughly.