Garlic Planting Calculator

Garlic is planted once a year, in fall, and how much you need depends on the size of your bed and how closely you space the cloves. This garlic planting calculator takes the length and width of your bed, the spacing between cloves and between rows, and the type of garlic, then tells you how many cloves fit, how many seed bulbs to buy and how much straw or leaf mulch to have ready for winter. It is built for US gardeners and works in feet and inches.

Planning ahead matters with garlic because you buy seed bulbs once, plant them within a short window before the ground freezes, and wait until the following summer to find out whether you planted enough. A few minutes with the calculator now saves a second trip to the garden center, or a half-empty bed.

How to use the garlic planting calculator

1. Enter the bed length and width in feet. Measure the planting area only, not the paths. If you are planting several beds, run each one separately and add the totals.
2. Choose the space between cloves in a row. Six inches is the most common choice. Go down to 4 inches for small cloves in a tight bed, or up to 8 inches for large hardneck or elephant garlic.
3. Enter the space between rows in inches. Rows 6 to 12 inches apart are typical for hand-tended beds. The tool starts at 10 inches, which leaves room to hoe or hand-weed between rows.
4. Pick the garlic type. Hardneck, softneck and elephant garlic differ in how many cloves each bulb contains, and that decides how many bulbs you need to buy.
5. Read the results. You get the number of cloves to plant, the row layout, the seed bulbs to buy including a 10% spare, and the cubic feet of mulch for a 4 inch winter blanket.

The layout counts whole rows and whole cloves only, so the clove count is rounded down. The number of bulbs to buy is rounded up, so you are never short.

The garlic planting math

Garlic is planted on a simple grid, so the arithmetic is straightforward. Lengths are converted to inches so they match the spacing you enter.

Cloves per row = bed length (ft) × 12 ÷ spacing in the row (in)
Rows = bed width (ft) × 12 ÷ row spacing (in)
Cloves to plant = cloves per row × rows
Seed bulbs to buy = cloves to plant × 1.1 ÷ cloves per bulb
Mulch (cu ft) = length × width × 4 ÷ 12

Worked example: a 10 by 4 foot bed

You have a bed 10 feet long and 4 feet wide, with cloves 6 inches apart in rows 10 inches apart. Each row holds 10 × 12 ÷ 6 = 20 cloves. The bed has 4 × 12 ÷ 10 = 4.8 rows, which rounds down to 4 whole rows. That is 20 × 4 = 80 cloves. If you are growing hardneck garlic at about 6 cloves per bulb, you need 80 × 1.1 ÷ 6 = 14.7, so buy 15 bulbs. A 4 inch layer of mulch over the 40 square feet takes 40 × 4 ÷ 12 = 13.3 cubic feet, which is about seven bags of 2 cubic feet.

Worked example: a 4 by 8 foot raised bed

A raised bed 8 feet long and 4 feet wide, planted on a 6 inch grid in both directions, holds 8 × 12 ÷ 6 = 16 cloves per row and 4 × 12 ÷ 6 = 8 rows, for 128 cloves. With softneck garlic at about 10 cloves per bulb, you need 128 × 1.1 ÷ 10 = 14.1, so buy 15 bulbs. The mulch comes to 32 × 4 ÷ 12 = 10.7 cubic feet.

Quick reference by grid spacing

If you plant on an even grid, the number of cloves per square foot depends only on the spacing:

• 4 inch grid: 9 cloves per square foot
• 6 inch grid: 4 cloves per square foot
• 8 inch grid: about 2 cloves per square foot (2.25)

So a 4 by 8 foot bed of 32 square feet takes 288 cloves on a 4 inch grid, 128 on a 6 inch grid and about 72 on an 8 inch grid. Tighter spacing fits more cloves but tends to produce smaller bulbs, because each plant has less soil to draw from.

Hardneck, softneck and elephant garlic

The type you choose changes both your clove count and your growing plan, so it is worth knowing the differences before you shop.

Hardneck garlic sends up a stiff flower stalk, called a scape, in early summer. It usually forms a single ring of large, easy-to-peel cloves, commonly around 4 to 9 per bulb, and it tends to cope better with cold winters than softneck types. It generally does not store as long as softneck, so plan to use it within several months. The calculator assumes about 6 cloves per bulb for hardneck.

Softneck garlic has no scape and a flexible stem, which is why it is the type used for garlic braids. It forms many cloves in overlapping layers, often 10 or more per bulb, and it usually stores longer than hardneck. It tends to do best where winters are mild, though many gardeners in colder areas grow it successfully with good mulch. The calculator assumes about 10 cloves per bulb.

Elephant garlic is not true garlic. It is closely related to leeks and produces very large bulbs with only a few big cloves, about 4 in the calculator. The flavor is milder. Give it more room than regular garlic, and plant it a little deeper.

These clove counts are averages. Varieties within each type vary, and clove counts change with bulb size and growing conditions, so check the description from your seed garlic supplier and adjust if their bulbs run larger or smaller.

When to plant garlic

Garlic needs a stretch of cold weather to form proper bulbs, and it needs time to grow roots before the ground freezes. The usual advice is to plant a few weeks before the soil freezes solid, so the cloves root in but do not send up much top growth before winter. In much of the northern United States that means roughly late September through October. In areas with milder winters, planting runs later into the fall, often November or even December.

The easiest way to find your window is to look up your average first fall frost date and plant in the weeks after it. Our frost dates by ZIP code tool gives you the average first and last frost for your area, and the guide to frost dates explains how to use them. If a few weeks have slipped by, planting late is usually better than not planting. Cloves put in shortly before the ground freezes will often still produce a good crop, with somewhat smaller bulbs. For a full walk-through of timing by region, see how to plant garlic in fall.

How to plant garlic, step by step

1. Choose a sunny, well-drained spot. Garlic wants full sun and soil that does not hold standing water, which can rot the cloves over winter. Raised beds work well for heavy soil.
2. Loosen the soil and add compost. Work an inch or two of finished compost into the top spade’s depth of soil. Our compost calculator shows how much you need for the area.
3. Break the bulbs into cloves just before planting. Keep the papery skin on each clove. Set aside the biggest cloves for planting and use the small ones in the kitchen, because large cloves tend to grow large bulbs.
4. Plant pointed end up. Push each clove into the soil so the tip sits about 2 inches below the surface. Some northern growers plant 3 to 4 inches deep for extra winter protection.
5. Space the cloves. Use the spacing you chose in the calculator, and mark your rows with string so they stay straight.
6. Water lightly. A good watering settles the soil around the cloves. After that, normal fall rain is usually enough, but water if the fall is dry so roots can establish.
7. Mulch. Once the soil has cooled, spread about 4 inches of straw or shredded leaves over the bed. Many growers use anywhere from 3 to 6 inches.

Choosing seed garlic

Buy seed garlic from a garden supplier, seed company or local grower rather than the supermarket. Grocery store garlic is often treated to prevent sprouting, may carry diseases, and is rarely matched to your climate. Seed garlic is sold for planting, and many suppliers describe each variety’s flavor, clove size and hardiness.

Order early. Popular varieties can sell out by late summer or early fall, and planting time arrives quickly. When your bulbs arrive, keep them in a cool, dry, ventilated place until planting. Choose firm, plump bulbs and avoid any with soft spots, mold or blue-green patches.

Once you have a variety you like, you can save your best bulbs from each harvest and replant them the following fall. Save the largest, healthiest heads, since replanting the biggest bulbs each year tends to keep the crop strong. Rotate the planting location, and avoid planting garlic or other alliums such as onions and leeks in the same bed for several years running, which lowers the risk of soil-borne disease.

Mulching garlic for winter

A blanket of mulch protects shallow roots from freeze and thaw cycles that can heave cloves out of the soil, keeps the soil from drying out, and suppresses weeds in spring. Straw and shredded leaves are the usual choices because they are light, cheap and break down slowly. The calculator figures a 4 inch depth, which is a good middle ground. Use less in mild climates and more where winters are severe.

In spring, the green shoots push right through the mulch. If the mulch is very thick and the shoots seem stuck, pull it back gently, but leave the rest in place to hold moisture and block weeds. If you need to work out mulch for the rest of the garden, use the mulch calculator.

Spring and summer care

Shoots usually emerge in late winter or early spring. From then until the bulbs start to swell, garlic is growing leaves, and the leaves are what feed the bulb, so healthy foliage matters. A few simple habits make the difference.

• Feed in spring. Garlic responds to nitrogen early in the season. A side-dressing of compost or a nitrogen fertilizer when the shoots are a few inches tall is common practice. Stop feeding by late spring, as the bulbs begin to form.
• Water steadily. About an inch of water a week, from rain or hose, is a common guideline during active growth. Stop watering a couple of weeks before harvest so the bulbs can cure properly. The garden watering calculator can help you work out how much water your bed needs.
• Keep weeds down. Garlic is a poor competitor because of its narrow leaves. Mulch and regular hand weeding keep it growing well.
• Cut the scapes. On hardneck garlic, snip off the curling flower stalk once it has made a loop or two. This sends the plant’s energy into the bulb, and the scapes are tasty in stir-fries and pesto.

When and how to harvest garlic

Garlic planted in fall is usually ready the following summer, often from late June through July depending on where you live and the variety. The leaves tell you when: once the lower leaves have turned yellow or brown but several upper leaves are still green, the bulbs are close to ready. Dig one test bulb to check. The head should be well formed and the cloves should fill out their wrappers.

Loosen the soil with a garden fork and lift the bulbs rather than pulling by the stem, which can break it. Brush off loose soil without washing. Cure the bulbs for two to four weeks in a shaded, airy, dry place, then trim the roots and stems. Properly cured garlic stores for months, with softneck types generally keeping longest. Save your best bulbs for replanting.

Fitting garlic into your garden plan

Garlic goes into the ground in fall and comes out in midsummer, so it occupies its bed for about nine months and leaves it free for a late crop afterward. Many gardeners follow garlic with quick greens or a summer-sown cover crop. Because the bed is busy over winter, it is worth placing garlic where it will not get in the way of spring crops. Use the garden planner to map where it fits, and the plant spacing calculator for the crops that follow. For the other end-of-season jobs, our fall garden prep guide covers the rest of the list.

Common garlic planting mistakes

• Planting grocery store garlic. It may be treated or diseased and is not matched to your climate. Buy seed garlic.
• Planting too early. Cloves planted in warm weather can send up too much top growth, which is then damaged by winter cold. Wait for the soil to cool.
• Planting upside down. The pointed end goes up. Cloves planted the wrong way may still grow but take longer to emerge and often produce weaker plants.
• Skipping mulch. Without winter cover, cloves can heave out of the ground during freeze and thaw cycles.
• Crowding the bed. Cloves planted too close together produce small bulbs. Stick to at least 4 inches, and 6 inches if you want large heads.
• Waterlogged soil. Cloves sitting in wet soil rot. Choose a well-drained spot or use a raised bed.
• Watering too late into summer. Stop a couple of weeks before harvest, or the bulbs may not cure well.

Frequently asked questions