Why Is My Garlic Rotting?

If you pulled a garlic bulb expecting fat, firm cloves and instead found mush, slime, or a fuzzy white mat at the base, something in the growing or storage chain went wrong. Garlic rot almost always traces back to one of four culprits: a soil-borne fungus called white rot, Fusarium basal rot, plain old waterlogged soil, or mistakes made at harvest and during curing. The good news is that each of these leaves distinct clues, and once you read those clues correctly you can stop the loss this season and keep it from spreading to next year’s crop. Below, work through each likely cause, how to diagnose it, and exactly how to fix it.

Cause 1: White Rot (Sclerotium cepivorum)

White rot is the most feared garlic disease for a reason: it is caused by the soil fungus Sclerotium cepivorum, and once it is in your soil it can stay there for two decades or more. It attacks all alliums — garlic, onions, leeks, shallots, and chives — and a single infected bed can keep reinfecting crops long after you have forgotten the original outbreak. It is most aggressive in cool soil, roughly 50–65°F, which is exactly the temperature range garlic grows through in spring.

How to diagnose it

Look first at the foliage above ground: white rot causes leaves to yellow from the tips down and the whole plant to wilt and collapse earlier than its neighbors, often in patches rather than uniformly across the bed. When you lift a suspect plant, the roots will be rotted away and the base of the bulb will be covered in a fluffy, cottony white mycelium — that white fungal mat is the signature. The clinching evidence is tiny black structures, about the size of poppy seeds or pinheads, embedded in the white growth or on the rotting basal plate. Those are sclerotia, the survival bodies that overwinter in soil and germinate when they sense allium roots nearby. If you see the white fluff plus black specks, treat it as white rot until proven otherwise.

How to fix it

There is no fungicide that reliably cures white rot in a home garden, so management is about containment, not rescue. Remove every infected plant immediately, along with the soil clinging to the roots, and bag it for the trash — never compost it, because the sclerotia will survive a home compost pile and spread. Do not move soil, tools, or boots from the infected area to clean beds without cleaning them first; a quick scrub plus a 10% bleach rinse on tools and trowels stops you from carrying sclerotia around. Then stop growing any allium in that ground for a minimum of four years, and longer if you can manage it — eight years is safer given how long the sclerotia persist. Some growers slow an infestation by planting in raised beds filled with fresh, allium-free soil, which physically separates new crops from the contaminated layer. If your garlic disease problems keep recurring, our broader guidance in the Plants & Flowers hub covers crop rotation planning across the whole vegetable garden.

Cause 2: Fusarium Basal Rot

Fusarium basal rot is caused by Fusarium oxysporum f. sp. cepae, another soil-dwelling fungus, but it behaves very differently from white rot. Where white rot prefers cool conditions, Fusarium thrives in warm soil — it becomes most damaging once soil temperatures climb above 75°F, which often means it shows up late in the season as your garlic approaches maturity or during a hot spell. It frequently enters through wounds: roots damaged by cultivation, feeding by onion maggots, or general plant stress give the fungus an easy door.

How to diagnose it

Pull a declining plant and turn the bulb over to inspect the basal plate — the hard disc at the bottom from which the roots emerge. Fusarium produces a soft rot there that runs from pink to reddish-brown to brown, and the rot works its way upward into the cloves from below. The roots are often shriveled or rotted, and in humid conditions you may see a sparse, light pinkish or white mold on the basal plate, but you will not find the dense cottony mat or the black sclerotia that mark white rot. That absence of black specks is the easiest way to tell the two apart. Above ground, Fusarium-infected plants yellow and die back prematurely, and bulbs that look acceptable at harvest can continue rotting from the base in storage.

How to fix it

Like white rot, Fusarium basal rot cannot be sprayed away once it has taken hold, so prevention and culling carry the load. Remove and discard infected bulbs rather than storing them, since they will spread soft rot to healthy neighbors in the crate. Because the fungus exploits wounds and heat stress, focus on growing vigorous, unstressed plants: avoid nicking roots when you weed close to the row, keep onion maggots in check, and make sure plants are not baking in compacted, droughty soil during warm spells. Rotate alliums out of the affected bed for three to four years to let soil populations decline. When you replant, start with clean, certified seed garlic, and where the disease has been a persistent problem, look for garlic varieties described as Fusarium-tolerant. Planting at the right depth and keeping consistent moisture so plants never swing between drought and flood also reduces the stress that opens the door to infection.

Cause 3: Wet, Waterlogged Soil and Poor Drainage

Not all rot is a named pathogen — a great deal of garlic rot is simply the result of growing a bulb crop in soil that holds too much water. Garlic roots need oxygen, and saturated soil drives the air out, suffocating the roots and creating exactly the wet, low-oxygen conditions in which opportunistic rots flourish. Chief among these is Botrytis neck rot (Botrytis species), which establishes in the neck and upper bulb, plus a general bacterial and fungal soft rot that turns cloves slimy and foul-smelling. Heavy clay, beds in a low spot where runoff collects, and overwatering in the weeks before harvest are the usual setups.

How to diagnose it

Drainage-driven rot tends to be general rather than localized to the basal plate. Affected cloves go soft, watery, and translucent, often with a sour or rotten smell, and a squeezed bulb may weep liquid. Botrytis neck rot specifically shows up as a soft, water-soaked area at the neck where the leaves meet the bulb, sometimes with a gray fuzzy mold and, later, small black sclerotia near the neck and outer scales — but the rot pattern starts at the top of the bulb, not the bottom, which separates it from basal rots. The strongest diagnostic clue is the site itself: if the bed stays puddled after rain, the soil is dense and slow to drain, or you have been watering heavily right up to harvest, drainage is the prime suspect.

How to fix it

Fix the water before you fix anything else. The single most effective step is to grow garlic in raised beds 8–12 inches high, which lift the root zone above standing water and drain freely even after heavy rain. Amend heavy or clay soil generously with compost and other organic matter to open up its structure and improve infiltration. Choose a planting site that does not collect runoff, and if your whole garden sits low, consider directing water away with a simple swale. On the watering side, garlic needs about an inch of water per week during active growth, but you should taper off and then stop watering two to three weeks before harvest so the bulbs firm up and the wrappers dry rather than sitting wet in the ground. For more on building free-draining beds, our guide to raised-bed and container growing walks through soil mixes and bed construction.

Cause 4: Storage Rot from Harvest and Curing Mistakes

Sometimes the bulbs come out of the ground looking fine and then rot weeks later in the pantry or garage. This is storage rot, and it is usually self-inflicted: harvesting at the wrong time, skipping or rushing the cure, bruising bulbs during handling, or storing them in conditions that are too warm and humid. Garlic that is not properly cured and dried still holds moisture in its neck and wrappers, and that trapped moisture is a perfect medium for Botrytis, Fusarium that hitched a ride from the field, and blue-green Penicillium mold.

How to diagnose it

Storage rot reveals itself in the weeks and months after harvest rather than in the bed. Bulbs feel soft when you squeeze them, individual cloves shrivel or turn brown and dry from the inside, and you may see powdery blue-green mold (Penicillium) or gray fuzz on the wrappers. A vinegary or fermented smell points to soft rot. Think back to harvest: if you pulled the bulbs while the tops were still mostly green, the wrappers were thin and the bulbs immature; if you waited until the tops had completely died and the soil was wet, the bulbs may have started splitting and absorbing moisture. Either timing error, combined with a poor cure, shows up later as collapsing bulbs in the crate.

How to fix it

Start with timing. Harvest when roughly the bottom third to half of the leaves have yellowed and browned but several green leaves remain at the top — each green leaf corresponds to a protective wrapper layer around the bulb, and you want those wrappers intact. Dig, do not yank, to avoid bruising the bulbs, and never wash them. Then cure: hang or rack the plants in a single layer with the tops still attached, in a shaded, dry spot with strong air movement, for two to three weeks at 60–80°F. A fan makes a real difference in humid climates. The cure is finished when the wrappers are papery, the neck is fully dry and tight, and the roots are brittle. Trim the roots and cut the tops to about an inch (or braid softnecks), then store cured bulbs in a cool, dry, dark place around 50–60°F with good airflow — mesh bags or open baskets, never sealed plastic. Inspect periodically and pull any softening bulb before it spreads.

How to Prevent Garlic Rot Next Season

Prevention pulls together the lessons from all four causes into a single routine. It starts with seed: plant only firm, healthy, certified disease-free seed garlic from a reputable source, and never plant cloves from a bulb that showed any rot, because Fusarium and white rot ride along on infected stock. Practice deliberate crop rotation — keep garlic and all other alliums off any given bed for at least four years, extending to eight where white rot has appeared, so soil-borne fungi starve for lack of a host. Build the bed for drainage with raised beds and plenty of compost so roots never sit in water, and follow a watering schedule of about an inch per week that stops two to three weeks before harvest.

Sanitation matters more than gardeners expect. Clean tools, trowels, and boots between beds, especially after working in any area with a history of disease, and never compost rotted alliums. Give plants enough space — roughly 6 inches between cloves and 8–12 inches between rows — so air moves through the canopy and foliage dries quickly after rain or dew, which discourages Botrytis. Plant at the correct depth (about 2 inches deep, pointed end up) and mulch to buffer soil temperature, which helps avoid the warm spells that favor Fusarium. Finally, treat the cure as part of growing, not an afterthought: a thorough two-to-three-week cure with good airflow is what converts a healthy harvest into bulbs that keep for months. For other allium and vegetable troubleshooting, browse the related growing guides in the Plants & Flowers section.