Growing Garlic in Ontario

In Ontario, garlic is mostly planted in the fall and harvested the next summer. The following provides information on growing garlic in Ontario, including, best varieties, planting techniques, types of seed, soils, fertility, weeding, harvesting, storage methods and pest control.

Garlic belongs to the Alliaceae family, which includes other crops such as shallots, onions and leeks. Most garlic grown in Ontario is sold as fresh whole bulbs, green spring garlic or scapes. A smaller portion of the harvested garlic is processed into products such as chopped garlic, pickled garlic or powder.
 

Varieties

There are two types of garlic grown in Ontario called hardneck and softneck. Hardneck varieties bolt during late spring or early summer, producing a flower stalk called a scape. At the tip of the scape is a capsule containing bulbils (small aerial cloves) is produced instead of a true flower. 

Depending on the hardneck variety, bulbils come in a wide range of sizes and number produced per plant. Bulbils can be used as seed for planting, but usually require at least two seasons to develop into full sized bulbs. Softneck varieties do not produce a scape, although they sometimes produce bulbils in the stock of the plant, especially in cold climates.

In general, hardneck varieties are considered to be very winter hardy, have bulbs with large cloves and produce fewer cloves per bulb than softnecks. Softnecks tend to be harvest 7 to 10 days before the earliest hardnecks and have a longer storage life than hardneck varieties.

Hardneck garlic produces anywhere from 4 to 12 cloves per bulb depending on the variety and growing conditions. Specific family groups (which have different varieties within them) grown in Ontario include Marbled Purple Stripe, Rocambole, Porcelain, and Purple Stripe.

Softneck garlic varieties produce an average of 8 to 14 cloves per bulb. In colder regions, the number can be as low as 6 per bulb and warm southern regions it can be as high as 25 cloves per bulb. The two Softneck family groups grown in Ontario include Silverskin and Artichoke.

Since cultivated garlic plants do not produce true seeds, there is no exchange of genetic material that occurs between different strains of garlic.This means that all garlic is propagated vegetatively from cloves or bulbils, resulting in new plants being a clone of their parent plant. In other words, varieties stay genetically the same over time no matter how or where they are planted.

 Garlic Varieties
Purple Stripe (left) and Rocambole (right) garlic varieties.


Planting

Garlic is a perennial plant that requires a cold period for proper bulb growth to occur. In Ontario, garlic is generally planted in the fall and harvested the following summer. Although fall planting is recommended, it is still possible to plant in the spring (see Growing Garlic in Spring for more info). If doing so, the seed bulbs must be placed in cold storage prior to spring planting to allow proper bulb development during the growing season.

It is important that garlic is planted at the right time before winter.  Planting too early or too shallow risks having the shoots emerge above the soil surface and being exposed to extremely cold winter temperatures. This can cause die back of the leaves that have emerged or even death of the plant if the conditions are severe enough.

If planted too late, there is a risk that cloves will not develop a large enough root system in order to establish themselves before winter arrives. In Ontario, this usually means planting around October 15th, however, anytime from the beginning of October until the ground freezes is appropriate.

If planting is done at the right time, a strong, well-established overwintering plant will explode out of the ground in spring as soil and air temperatures warm up. If moisture and fertility are adequate, large healthy plants will develop before bulbing takes place. These large plants will then have the ability to produce maximum sized bulbs because of the large leaf surface area which is able to contribute more energy to the bulbing process. 

When possible, it is also important that cloves are planted with the pointed side up. Cloves planted on their sides can still grow nice bulbs, however, they sometimes develop curved stocks and misshapen bulbs. Many commercial growers plant cloves on their sides using seeding equipment, however, most gardeners and market growers, plant by hand with the tips pointed up.

Seed garlic should be kept as whole bulbs right up until just before planting. Cloves tend to start dehydrating and deteriorate quickly once they have been "cracked" and the bulbs are no longer intact.

Dry bulbs are usually easier to crack and brake into cloves than damp bulbs. The cracking process can be done using mechanical devices or by hand. Mechanical cracking is much faster and is much less work, however, it has a greater potential to physically damage the cloves during the process.

Garlic Seed Cloves
High quality garlic seed cloves ready for planting.
 

The number of seed bulbs required for planting ranges from 5000 to 9000 bulbs per acre (100 to 200 bulbs per 1000 square feet), depending on the variety planted and spacing used. Cloves should be spaced 4 to 6 in inches (10 to 15 cm) apart within the row.

Wider spacing will usually allow for larger bulbs to be produced and easier weeding during the growing season. Spacing between rows can range from 8 to 16 inches (20 to 40 cm)  depending on the planting, weeding and harvesting methods. Most growers use a spacing of between 10 and 12 inches (25 and 30 cm).

Some Ontario growers use bulbils as a seed source. Depending on the variety, capsules can contain anywhere from four to a few hundred bulbils. One advantage of planting bulbils is that it allows growers to increase their planting stock quickly and helps reduce some soil-borne diseases from the planting stock. The disadvantage is that it can take several years of successive plantings to achieve good-sized bulbs from the initial bulbil planting. This delay is why most growers only use cloves for planting.

Bulbils tend to dehydrate very easily because of their small size and loose wrappers.This means that bulbil capsules should only be broken open and individual bulbils removed just prior to planting. Bulbils can be planted closer together then cloves, however, they can be hard to weed if planted to closely. An in-row spacing of between 1 and 4 inches (3 and 10 cm) is a good range for most growers. 

Irrigation is very important for bulbil seedlings due to their shallow root systems. They should be watered regularly and throughout the growing season. 

Rocambole Bulbils

Capsule containing large Rocambole bulbils.


Soils and Fertility

Garlic grows well on a wide range of soil types including both sand and clay. It can be cultivated anywhere in Ontario that can grow cool season vegetables.

High organic matter soils are ideal because of their high moisture and nutrient holding ability. These soils are also less prone to crusting, settling or compaction issues. Very heavy soil types can be a challenge and hard to work with, especially under wet. Intensive soil management practices are required on light sandy soils due to their low moisture-holding capacity.

Garlic is a heavy feeder and grows best on fertile soils. Taking a soil test before planting garlic is always recommended in order to verify nutrient levels. If fertilizer (conventional or organic) is required, all the phosphorus and potassium should be added and incorporated before planting.

About 1/3 of the Nitrogen should be added just before or just after planting in the fall. The remainder should be split into several applications starting first thing in spring and ending about one month before harvest. 

The following are general fertility recommendations for garlic in Ontario, however, they could be higher or lower depending on the soil type, length of growing season and previous crop grown.

Nutrient

Pounds per Acre

Pounds per 1000 ft2

Nitrogen

120 lbs (55 kg)

3 lbs (1.3 kg)

Phosphorus

160 lbs (73 kg)

4 lbs (1.8 kg)

Potassium

150 lbs (68 kg)

4 lbs (1.8 kg)

Sulphur

30 lbs (14 kg)

1 lb (0.5 kg)

Fertility recommendations for growing garlic. 

 

Planting Location 

It is best to plant garlic in a sheltered location where good snow cover occurs. This will protect the cloves over winter and help prevent winter kill. Adequate shelter also reduces wind speeds which prevents wind erosion, especially on light sandy soils.

It is important to pick a location with good drainage, especially on heavier soils. There should be proper access to water if irrigation will be required. Large trees close to the planting area should be avoided, as well as any areas that are infested with perennial weeds.

Growing Big Garlic
 

Mulching

Many Ontario growers mulch their garlic for the winter. Mulching helps moderate soil temperatures and keeps the cloves protected from fluctuating temperatures. There are different mulches that can be used, however, it is important to ensure that they are not contaminated with garlic pests, such as nematodes, bulb mites, diseases or weed seeds. Straw is the the most commonly used mulch and should be applied 10 to 15 cm deep directly over the planted garlic.

In spring, many growers remove the mulch completely once the threat of extreme cold is gone. This is to help minimize disease during wet weather and make weeding easier. Others growers leave it on for the whole season to help conserve moisture and provide a barrier for weed control.

 Straw Garlic Mulch
Garlic rows covered with straw mulch for the winter.


Irrigation

Garlic requires consistent moisture throughout the season to maximize its growth. Dry soil conditions, especially during the bulbing phase, will result in significantly smaller bulb sizes.

On clay and loam soils, approximately 1 inch (2.5 cm) of water per week is required during the growing season. On sandy soils, 2 inches (5.0 cm) or more of water can be required during hot, dry weather.

The best time of day for irrigation is during the morning or mid-afternoon. This allows enough time for the plant foliage to dry before cooler temperatures arrive in the evening. Irrigation should be stopped once the garlic has matured and it is almost time to harvest. This will help with the harvesting process and improve the conditions of the bulb wrappers by reducing their deterioration.


Scape Removal

Hardneck garlic varieties produce a scape that should be removed if maximum bulb size is desired. Research shows that bulb size can be reduced by as much as 30% when scapes are not removed. This is because energy is diverted to growing bulbils instead of increasing bulb size. Remove scapes by snapping or cutting them just after the have one or two curls (depending on the variety), but before they straighten out.

Garlic Scape
A Purple Stripe garlic scape ready for removal.


Harvest

Garlic bulbs continue to grow in size during late spring and summer until the leaves of the plant begin to die. This process starts with the lower leaves as they dry and turn brown from the tips towards their base.

Harvesting should begin when 30%-50% of the leaves have died and turned brown. This usually means about 3 to 5 leaves having died and 3 to 5 still green, depending on the variety.

Bulbs that are harvested too early will be immature and will likely shrivel when cured. Late harvested bulbs tend to be stained and often have deteriorated wrappers with exposed cloves.

For small growing areas of garlic, hand harvesting can be done by using a pitch or broad fork to loosen the soil and make removal easier. Large plantings of garlic are usually harvested mechanically with an under-cutter blade pulled by a tractor that cuts the roots and loosens the soil, making harvesting by hand less work. For very large farms, there is mechanized equipment that can be used to lift the bulbs and remove the tops all automatically in one operation.

Curing

Curing is the process of drying bulbs in order to increase storage life. This is done by reducing moisture content which results in the reduction of microbial and fungal growth.

Garlic should be cured immediately after harvest and can be left in the field to begin drying for a couple of days. Plants should be laid on the ground in single layer rows. When laying down the garlic plants, use the tops to cover the bulbs of the previous row to protect them from sun scalding.

Alternatively, the garlic can be removed from the field immediately after harvest and brought inside for the entire curing process. Plants can be tied in bundles of 10 and hung to dry or the tops can be removed and the bulbs placed into slotted crates, on wire racks or on open trays in a well ventilated area.   

Similar to bulbs, bulbils must be cured prior to storage. Harvest scapes with the bulbil capsule intact just prior to garlic bulb harvest. Once harvested, bunch, tie and hang scapes to dry for a few weeks. Once dried, remove the bulbil capsules and store them in a dry location until the time of planting.

 Harvested Garlic
Harvested garlic laying in the field to dry for several days.


Storage

Garlic that is going to be used for food consumption is best stored at 0°C-4°C with a relative humidity of 60%-70%. Higher humidity should be avoided, as it creates the perfect environment for moulds and root growth to develop.

Food garlic that is stored at room temperature usually dehydrates faster, however, doesn't require specialized refrigeration.

Garlic that is to be used as seed for planting, should be stored above 14°C to prevent sprouting and below 21°C with a relative humidity of 60%-70% to prevent dehydration.

Hardneck varieties can be stored up to 4 months at room temperature, while softneck varieties can store up to 10 months. When using specialized refrigeration with humidity control, storage life can be extended to 5-10 months for hardnecks and well over a year for softneck varieties. 


Weed Management

Garlic plants are very weak competitors and require dedicated weed control in order to maximize bulbs sizes. Weeding can be done with hand hoes, wheel hoes, tillers, mechanical cultivation with a tractor, mulching or with herbicides.

Garlic plants have very shallow roots that can be damaged easily, meaning that care should always be taken when tilling or cultivating. Damage to the garlic roots can reduce yields significantly.

Weed Free Garlic Plants
Garlic field that has been weeded several times throughout the growing season.

Insects and Diseases

There are a number of pests and diseases that affect garlic in Ontario. Some occur frequently, while others are rarely seen on most farms. The most common pests include, Fusarium basal plate rot, Penicillium mould, leek moth, bulb and stem nematode, and viruses.


Fusarium Basal Plate Rot

Fusarium Basal Rot is a fungal disease caused by Fusarium oxysporum that affects garlic and other alliums. The fungus can live for many years in the soil. Infections are often linked to some sort of mechanical damage or pest injury and occur most often at temperatures of 25 to 29°C (77 to 84°F). 

Symptoms include wilting and dieback of the leaves starting at the tips during the middle to late part of the season. Foliage death can take up to several weeks. Rot usually affects all of the bulb base and can move into the bulb itself. Affected tissue appears brown and watery when bulbs are cut open. Infected bulbs can look normal at harvest, but can eventually begin rotting in storage.

Fusarium Basal Rot is managed by using a 4 year or longer crop rotation, planting clean-seed and minimizing mechanical or pest injury.

 

Penicillium Mould

Garlic moulds are caused by several Penicillium species and can be found in both stored and planted garlic. Some moulds thrive in dry conditions, while others do well under very wet conditions. These fungi are common in the soil growing on infected animal and plant debris. Disease symptoms often start as pale blemishes, yellow lesions and soft spots. As the infection progresses a blue-green mould eventually develops on the lesions. In later stages of the disease, bulbs may completely deteriorate and decay. 

In planted garlic, the fungus tends to attack freshly planted cloves in warm climates and newly emerged plants in cold winter climates. Sometimes fall infection of the cloves leads to winterkill. If not killed, it leads to weak yellow looking young plants in spring.

Infections are usually spread from infected bulbs during the cracking process, moving spores onto the cloves that will be used for planting. Penicillium moulds do not move from plant to plant once the garlic has been planted.    

Penicillium moulds are primarily controlled by preventative measures. Minimizing the transmission of spores during storage and handling, planting only clean stock and preventing wounding or bruises of the bulbs are the main controls.    


Leek Moth

In North America, the leek moth is an invasive species from Europe that causes damage to onions, leeks and garlic. It was first found in eastern Canada in 1993 and has since spread to the United States. The Larvae cause damage when they penetrate the young leaves of plants in order to feed. This feeding weakens the garlic plants, sometimes causing them to not have enough energy to form properly sized bulbs. 

Organic pesticides such as spinoside or Bacillus thuringiensis var kurstaki (Btk) are effective controls of leek moth. These products mostly affect the larvae which are killed once they have begun feeding.  

Row covers, which physically block adult leek moth females from laying eggs on plants can be used. If done properly, they can be as effective as pesticides in reducing damage, sometimes eliminating it altogether.

Generally, leek moth is not a major pest of garlic, however, under certain weather conditions, their populations can increase drastically causing significant damage. Pheromone traps can be used to monitor moth pressure and notify you that control methods may be needed well before any damage has occurred. 


Bulb and Stem Nematode

The stem and bulb nematode, Ditylenchus dipsaci, is the most destructive pest of garlic in North America and much of the world. They are a microscopic worm-like parasite that damages plants and is very difficult to control once it is established in a growing area. The arrival of this pest can be devastating to a grower and make it very difficult to continue growing garlic or other alliums in the future. 

Nematodes can be found in seed, plant debris, soil or in water. They are most often introduced into a field on infected garlic cloves, but can also arrive with soil from equipment, in irrigation water or from overland flooding.   

Once present on a farm, nematodes can remain dormant in the soil, survive in plant residues and on weed hosts for many years and sometimes indefinitely. If garlic is planted again, even a small number of nematodes can reproduce very rapidly, resulting in a population explosion that can cause significant damage.

Infected garlic plants become swollen, leaves appear twisted and malformed, young roots and bulbs rot, severely infected plants turn yellow and die. Plants that do not die have bulbs that are deformed, short leaves and turn brown prematurely at harvest. Severely infected garlic bulbs are soft, discoloured and deformed, with portions of their root system missing. 

Planting clean nematode free garlic seed into nematode free soil is the primary control method. Use long rotations out of Alliums for 4 to 5 years to help keep populations low. Remove weeds and volunteer garlic plants every year, even when growing other crops. Proper sanitation should also be followed to prevent their spread from infested to non-infested fields. Tools and equipment should be carefully cleaned before moving them to another location.  


White Rot

White rot is a disease caused by the fungus, Sclerotium cepivorum.  Only Allium species such as garlic, onions and leeks are attacked by the fungus. 

It produces sclerotia that can live in the soil for many years. These sclerotia are able to infect plants from as deep as 12 inches below the soil surface. The disease is so infectious that it only takes one sclerotium to infect up to 30 plants. Infections occur most often in cool soils and are inhibited at temperatures above 29°C (75°F). 

Once the disease is in a field, it is very difficult, if not impossible to grow any Alliums including garlic. This can be devastating to a grower who may be required to no longer grow any of these crops. The disease spreads with infected bulbs, grazing animals, wildlife and transport of infested soil.

Symptoms include leaf decay at the base, yellowing, wilting, and falling over of plants. Roots will rot and the plant can be pulled from the ground easily. Fluffy mycelium can sometimes be seen on any remaining roots or the bulb. Affected bulbs may become watery, and outer scales crack as they dry and shrink. Small sclerotia (about the size of a cabbage seed) form in and on the surface of affected bulb parts. White rot continues to decay infected bulbs during storage if humidity is high enough.

Preventing the introduction of the disease is the primary control strategy. Plant only disease-free bulbs into disease-free soil. If working in fields that have been previously infected, wash equipment, vehicles and footwear before entering new areas to avoid moving infested soil.

If an infection is found, dig out all the infected plants along with those healthy plants growing next to them. Bring the plants and soil to landfill or burn.
 

Viruses

Almost all sources of garlic contain viruses, though most are dormant. This is because garlic is propagated by cloning which passes the viruses from one generation to the next. These dormant garlic viruses may not become visible or reduce yields until the garlic plant is stressed or growth is interrupted. 

The most common symptoms of virus infection are colour changes in the leaves. These include mosaics, streaking and sometimes complete yellowing. Leaves can also become distorted, forming strange shapes and the plants can become stunted. Symptoms can occur very early in the season or much later. 

Viruses can be spread during the growing season from insects or mechanical damage during work like weeding and weaker plants are more susceptible to infection.  

The spread of viruses can be controlled by roguing the garlic throughout the season. The bulbs from affected plants should not be used for seed.

Tissue cultured garlic planted as seed has been shown to be effective in producing “virus-free” garlic, however, it is not widely available. For the majority of growers, providing optimal growing conditions, doing regular roguing, and destroying any culls or plant residues is the best option for keeping viruses to a minimum.

About the Author: John Côté owns and operates John Boy Farms with his family who have been farming the same land for over 140 years. As an agronomist and experienced farmer, he helps others learn how to grow garlic successfully. He has written many articles and is the author of The Master Guide to Growing Big Garlic.