by Becky Sideman, UNH Extension Vegetable & Berry Specialist
Garlic harvest time is upon us, or fast approaching!
Determining time of harvest. Figuring out when to harvest can be tricky. The longer you wait, the bigger the bulbs, BUT the higher the risk of cloves separating. Harvesting too early results in smaller heads, with cloves not entirely filling their wrappers – and it can be more difficult to thoroughly dry garlic with numerous moist wrapper leaves. Here are some suggestions:
- The 3-4 older (bottom) leaves on the plants should have yellowed and senesced, but over half of the leaves should still be green and healthy. These healthy leaves make up the wrappers on the harvested bulb.
- Cloves should be wedge-shaped, and should fill their wrappers. The only way to see this is to pull a few test heads, and cut them in half to examine the cross-section. You can see a good photo of a mature head by Crystal Stewart, from Cornell University.
- Check maturity every week or so, beginning in late June/early July. It is better to harvest too early than too late; bulbs that have split apart are less marketable and will not store well.
Best harvesting practices.
- Harvest when the soil is slightly dry. This will make it easier to pull, clean, and dry the garlic.
- Lift garlic with an undercutter bar, mechanical harvester, or hand tools prior to pulling. Avoid bruising by being gentle during harvest. Remove excess soil by gently rubbing or shaking; don’t bang the heads against harvest baskets or anything else to remove the soil.
- Harvest garlic when it’s as dry as possible, to avoid bringing extra moisture into your drying and curing area.
Drying, curing and storing garlic.
- Immediately after harvest, move garlic into a shady spot (to avoid sunscald) to allow soil to dry in a well-ventilated area. Avoid direct sunlight and temperatures over 90F.
- High tunnels or greenhouses covered with shadecloth, or well ventilated barns, can make good drying spaces. Good air circulation is important. It will take 10-14 days to cure garlic.
- Garlic roots and stems may be trimmed before or after curing. If trimming while still green, leave stems about 6” long, and trim to final length once dry.
- The ideal long-term storage conditions for garlic are cool and dry conditions; 32F, 60-75% relative humidity. Seed garlic should be stored at warmer temperatures (50F).
Assessing garlic health. Harvest time is a good time to pay attention and look for signs of pathogens and diseases. This is especially true if you save your own seed garlic, or if you sell garlic that will be used as seed. For most garlic pathogens and diseases, the only effective management strategy is to be vigilant and cull problems quickly – so it pays to keep an eye out. Some of the most problematic pests & diseases are described below.
Leek Moth. Leek moth is a new pest for our region. Thus far, it has been found in Vermont, and in Coos County in NH. Signs of this pest on garlic include feeding damage on the scapes and leaves. See the Leek Moth page maintained by Cornell University for more information and photos. If you see something that you suspect is leek moth, please reach out to any member of the Vegetable & Fruit Team, or to Piera Siegert, the NH State Entomologist (contact info here).
Stem & bulb or garlic “bloat”nematode (Ditylenchus dipsaci). This pest has been found throughout NH, and is particularly damaging because it’s easily spread by saving and selling or replanting seed. Cool, moist conditions favor infestation by this tiny roundworm, and many parts of NH experienced prolonged periods of cool and wet conditions this year. Signs of this pest include 1) stunted plants that die prematurely and 2) stunted, underdeveloped, and misshapen bulbs. Some excellent photos are found in this University of Maine publication by Steve Johnson. If you believe you have this pest, please get it identified – one way to do this is to send it to Cheryl Smith at the NH plant diagnostic lab. This pest can spread quickly from seed stock that appears to be clean, so it pays to be vigilant.
White rot (Sclerotium cepivorum). This fungal disease is favored by cool and moist condition. Symptoms include yellowing leaves or stunted plants. Affected bulbs may rot, and fungal mycelia or sclerotia (black resting structures) may be visible on the bulbs. Some photos are found here. Because it spreads so quickly and is so destructive, this disease should also be diagnosed if you think you have it (NH plant diagnostic lab).
Fusarium basal plate rot (Fusarium oxysporum f.sp. cepae). Cheryl has received several samples of this disease already this year. As with the other issues mentioned above, one of the first indications of this disease is early senescence and yellowing of infected plants. Often, the basal plate and roots of heads are rotten, and there may be some discoloration of the bulbs. It can be difficult to distinguish between this disease and other problems (photos here), so submitting samples to a lab is really the only way to get a truly accurate diagnosis.
C. Stewart, Cornell University, Harvest considerations for garlic, S. Johnson, University of Maine, Bloat nematode in Maine garlic, S. Johnson, University of Maine, White rot in garlic and onions, M. Celetti, OMAFRA, Fusarium basal plate rot of onion and garlic , and R. Hazzard, UMass, Garlic harvest, curing and storage.