When Should I Quit Fertilizing My Garlic?

Planting Time

• Managing your fertilizer starts with planting garlic at the best time of year. Hardy in U.S. Department of Agriculture plant hardiness zones 3 through 8, garlic can be planted in fall or early spring. Fall planting consistently leads to larger and more flavorful crops. In cold climates, do this two to three weeks after your first frost and before the ground completely freezes. Garlic bulbs need a cold period to develop individual cloves instead of a single bulb. With fall planting, winter months provide this naturally. Buy your planting garlic from a source in a growing zone similar to yours for best results.

Autumn Amendments

• When planting in fall, begin your fertilizing program by preparing fertile, well-drained garden soil. Incorporate well-rotted compost into your garlic area. This equips the soil with all the nutrients necessary to support healthy root development before winter sets in. You can also incorporate 3 to 5 pounds of granular 10-5-5 fertilizer per 100 square feet as you prepare the planting bed. This is the only fertilizer your fall-planted garlic needs at this point. The goal is to stimulate root growth, but keep top growth restrained. Too much fertilizer promotes fast, tender growth that can be damaged by cold and weaken the garlic bulb.

Springing Forward

• Once spring arrives, garlic tops begin active growth. Wait until leaves reach 6 to 8 inches in height to begin spring fertilization. Apply a side dressing of well-rotted compost or broadcast granular 21-0-0 fertilizer at a rate of 1 pound per 100 square feet. This high-nitrogen formula promotes rapid foliage growth to fuel the waiting bulb. Garlic is highly efficient at using soil nutrients. Amendments other than nitrogen are unnecessary in spring. If gardening in poor soil, repeat this spring feeding every two weeks until the plants have four leaves. In mild areas where garlic reaches this stage before winter, do not apply spring fertilizer.

Pulling Back Again

• At five leaves, garlic bulbs begin to enlarge. Stop all fertilizer at this point. Continuing to fertilize diverts energy away from bulb growth. Focus your energy on eliminating weeds. Root competition inhibits garlic growth. If your variety has a hard central stem, called a scape, remove it to increase bulb size. Garlic can double in size in its final month. As hotter weather and longer days arrive, bulbs stop growing. Fall-planted garlic matures by mid to late summer. Smaller, spring-planted garlic won't be ready until fall. When stems yellow and fall over, harvest the crop. Enjoy your garlic and plan fertilizers for next season.