Garlic for Production of Planting Stock
Last modified February 5, 2010
Note: The information in this file is specific to production of garlic for planting stock, as suggested for growers producing garlic for the dehydration industry. More information on garlic types, cultural practices, and pest control can be found in the file Garlic.
All garlic to date is planted from cloves (commonly called "seed," "seed garlic," or "seed stock"). Production of garlic from true seed has been extensively investigated since the late 1980s, but production from true seed is not used commercially. Most garlic produced in Oregon for the dehydration industry is grown for planting stock for commercial garlic production in California, Nevada, and elsewhere. When production for planting stock exceeds requirements for that purpose, excess production has been used for dehydration or the fresh market.
Two types of silverskin garlic are commonly grown in the northwest for seed stock. These are known as California Early and California Late. Numerous strains of these exist, having been selected over the years by the various companies that produce them for dehydration or seed stock. Silverskin garlic rarely, if ever, produces seed stalks. Less commonly grown are several varieties of hardneck garlic.
In recent years, virus-free planting stock of California Early has been made available and is used by the processing industry. This virus-free garlic is much more vigorous and out yields standard garlic in raw product and dehydration efficiency characteristics. Virus-free planting stock is all proprietary. Its production by tissue culture and subsequent field isolation requirements and planting stock maintenance are complex so availability may be limited.
All planting stock for dehydration will be provided by the dehydration company who usually produces it, or arranges for it. Seed stock for other purposes must be obtained from reputable seed sources. To protect their fields from introduction of diseases, growers should discuss planting stock quality and seed stock treatment with their company field department.
Extreme care must be exercised in using pest-free planting stock. Bulbs and cloves used for planting can carry and transmit diseases such as Sclerotinia cepivorum (white rot), Fusarium cumorium, (basal rot), and possibly Botrytis allii and B. porri. The seed may also be infected by Penicillium, a fungus that can cause a decay of the seed pieces and reduce stand. Other important pests that can be carried on the seed stock are several species of nematode (stem and bulb). Some of these pests may render the soil unusable for further production of garlic, onions and related crops. Whenever possible observe the field from which the planting stock is to be obtained for these and other pests.
Silverskin garlic is planted at about 6-8 cloves per row foot (12-16 plants per bed foot) for California Early and 8-9 cloves per row foot (16-18 plants per bed foot) for California Late. This should produce a population of about 100,000 to 150,000 plants/acre. From 1600 to 2000 lb of California Early, and 1400-1700 lb of California Late cloves are needed to seed an acre. The higher populations are used for processing or planting stock purposes.
Garlic will grow in almost any well-drained, friable soil.
Depending on the type of garlic being produced, yields can range from 14,000 to 18,000 lb/acre. The harvest operation sequence includes topping, digging, sorting, loading, and transport to the dehydration facility.
Garlic is ready for harvest when the tops become partly dry and bend to the ground. After the tops have dried they may be partially removed by propane flaming. Care should be exercised so that garlic bulbs are not exposed above the soil surface and subjected to flaming damage. Flailing is used to complete top removal.
For immediate replanting, garlic tops are flailed off after they are down and dried and just before harvest. Several excellent topping and windrowing machines, such as the Vegi-Vac and Top-Air, are manufactured. Some dehydration companies have also built their own diggers, toppers, and windrowers. To loosen the bulbs and minimize the incidence of soil clods in the product, fields may be irrigated slightly to moisten the soil to just below the bulb. Then, as soon as possible (within a day or two), run a cutter bar beneath the bulbs and dig the bulbs with a chain digger, gathering several rows into one windrow 2-4 hours ahead of loading.
A paddle-wheel loader is used for loading. This equipment may be designed to allow for a crew of sorters to remove soil clods prior to loading into transport trucks. Loading machines are used in California by some processors that have electronic sorters to remove rocks or clods, but these have not been made available for use in Oregon.
Garlic not intended for immediate replanting may be dug after topping with a modified simple potato digger and windrowed on the soil surface for a brief (several hours) curing period, then hand placed into sacks or bins for final curing (10-14 days, or as needed) in curing shelters or in the field.
Garlic must be protected from sun scald, especially during periods of high temperature (over 90 F) and bright sunlight. Excessive exposure to sunlight may also result in greening.
If bulbs tend to shatter, late watering may be the cause (see irrigation section above). Other causes of shatter may be stem and bulb nematode infestation or too rapid drying of the bulbs after harvest.
Garlic intended for planting stock should not be placed in cold storage or in heated warehouses because of the adverse effect such temperatures have on growth of the planting stock. Optimum storage temperature for planting stock is about 50 F with a desirable range of between 40 F and 65 F. Storage at lower temperatures increases the production of rough bulbs, the sprouting of side-shoots and early maturity. Storage for extended periods at high temperatures may delay sprouting and maturity.
Garlic may be put in common storage where it may be held for 3 to 4 months or sometimes longer if the building can be kept cool (about 50 F), dry, and well ventilated.
Garlic planting stock is shipped in bulk truck loads of 30,000-40,000 lb directly from the field after a curing period as described above.
Oregon State University and industry representatives and growers developed an enterprise budget for Jefferson County in 1993. The budget assumes a yield of 17,000 lb/acre and a value of $0.14/lb for a total gross income of $2380. Variable costs per acre include pre-plant costs of $169; post-plant, pre-harvest costs total $386 and harvest costs at $0.02/lb or $340, making total variable costs $925/acre. Irrigation equipment, machinery and land accounted for a fixed cost of $172/acre. Total of all costs was $1098.