USDA Plant Hardiness Zone Map. Mapping by PRISM Climate Group, Oregon State University
What Type of Garlic Grows in my Location?
Hardneck or Softneck?
The United States Department of Agriculture has established a “Plant Hardiness Zone Map” which categorizes the United States into similar growing climates. Based on this Plant Hardiness Zone Map, literature reviews, and actual discussions with garlic growers across the United States, here are recommendations on what type of garlic you can grow at your location.
Many people ask: "Are Hardneck and Softneck Garlic different?" "Which of these should I grow?" "I live in Texas where it typically does not freeze in the winter; What type of garlic should I grow?" "I live in Ohio where it gets very cold in the winter, what garlic is best for me to grow?" "I planted hardneck seed garlic here in Florida and the cloves rotted in the ground! What did I do wrong?"
On-going research proves that classifying garlic is a complicated task. For a comprehensive overview of garlic classifications, please refer to The Complete Book of Garlic by Ted Jordan Meredith.
Garlic has been separated into three subspecies based on its ability to bolt. Garlic genotypes are categorized as non-bolting, semi-bolting, and bolting (Takagi, 1990; Kamenetsky and Rabinowitch, 2001; Etoh and Simon, 2002; Kamenetsky et al., 2004a,b) and differ considerably in bolting ability, scape length, and seed production (Mathew et al., 2010).
In general terms, most growers of Garlic commonly divide them into two main varieties or subspecies, the hardneck (ophioscorodon) and softneck (sativum). These are named based on the fact that the hardnecks develop a stiff stalk from the cloves in the ground, topped by mini aerial cloves called "bulbils". This process is often called "bolting". Sometimes these designations don't hold in reality, the stalks developing or not with different seasons, climates, and cultivars (cultivated varieties).
Types of Garlic
A useful distinction is the classification of garlic into softneck and hardneck types. All wild garlic is of the hardneck type but domestic garlic may be either hardneck or softneck. Both begin with leafy tissue in spring but hardneck garlic will produce a seed stalk in late May or June.
The softneck variety of garlic does not develop a flowering stalk (scape), so their stems stay soft and flexible, making them excellent for creating braids of garlic. Their soft stems equate to softneck. Softneck garlic normally grows best in climates with hot summers and mild winters. There are two common softneck garlic types; Artichoke and Silverskin. Artichokes are named for their resemblance to artichoke vegetables, with multiple overlapping layers containing up to 20 cloves. They are usually white to off-white with a thick, hard-to-peel outer layer. A few artichoke garlic varieties include: California Early, California Late, Early Red Italian, Italian Purple, Inchelium Red, and Italian Late. Silverskins garlic is layered like Artichokes and are also adaptable to a range of growing conditions but may bolt when stressed by cold weather. They have 14-24 reddish cloves on oblong-shaped bulbs with white wrappers. Silverskins are frequently used in garlic braids. Garlic plant varieties for silverskins include: ‘Polish White’ ‘Chet’s Italian Red’ and ‘Kettle River Giant.’ Softneck Garlic does not have a scape. Because they’re not spending energy growing this stem, they usually have more cloves than hardneck garlic. Softneck garlic is the most common variety found in grocery stores. Softneck garlic often have many smaller cloves and they sometimes form multiple layers of bulbs around the stem.
The hardneck variety develop a stiff stalk from the cloves in the ground, topped by mini aerial cloves called "bulbils". This stiff stalk equates to hardneck. Hardneck garlic was the original selection that evolved from wild garlic. Compared to the softneck types, they typically have fewer but larger cloves, are more colorful and come in a wide range of flavors. They grow well in the colder, northern climates. The majority of the garlic grown in the northern tier of the United States is hardneck. Hardneck Garlic refers to the thick stem or flower stalk that grows up in the middle of the bulb. As the plant matures, a scape (pig-tail shaped stem) forms at the top of the plant's stem, and it usually grows into a round squiggle. Most garlic growers cut the scapes off so that all of the plant’s energy is going to the bulb, not to the scape and/or flower. Hardneck garlic typically is hardier than softneck garlic and is a good choice for Zone 2 up to Zone 6. There are three main types of hardneck garlic: purple stripe, rocambole, and porcelain. Within these types, there are many named varieties, each with its own particular traits, such as flavor or hardiness. A few examples of named hardneck varieties include: ‘Music', Chesnok Red’ ‘German White’ ‘Polish Hardneck’ ‘Persian Star’ ‘Purple Stripe’ and 'Rosewood’. Many of these names were developed by private individuals who named the strain using their own name, or anything they desired. In other words, some garlic plant varieties may be virtually the same despite different names, and some with the same name may be very different from each other. Music garlic was believed to have been brought to Canada from Italy during the 1980s. The porcelain-type garlic was named for Al Music, a tobacco farmer turned garlic grower who introduced the variety to Canada
Selecting Garlic to Grow in your Climate
By selecting the proper garlic to plant, and planting the garlic at the right time, you too can enjoy a magnificent garlic reward. In very simple terms, hardneck garlic are the most rugged and cold-hardy of the garlic. They grow best in Hardiness Zones 2 up to Zone 6. In order to form healthy bulbs, they need to experience at least 10 weeks of cold. This period of cold exposure is known as vernalization. If the garlic plant does not experience a sufficient period of vernalization, it will not produce a bulb. Hardneck garlic is often more flavorful as compared to softneck garlic, and many varieties last up to 6 months if stored in a cool environment. If you live in an area where cool-season lawns (bluegrass, perennial rye, fine fescue) are the norm, a hardneck garlic seed is a good first choice. Gardeners in cold climates usually grow hardneck garlic. At GroEAT Farm, located in Bozeman, Montana, they only grow hardneck garlic.
Softneck garlic normally grows best in climates with hot summers and mild winters. ‘Nootka Rose’ and ‘Italian Late’ are all softneck garlics, known for their productivity. If you live where warm-season grasses such as zoysia and bermuda lawns thrive, softneck garlics are more often grown in these locations. Softneck garlic does not produce a flower stalk, but forms layers of cloves around a soft central core. Softneck garlic is the most common type found in the supermarket and is also the type to grow if you want to make garlic braids. Most softneck garlic varieties are suited to areas of mild winters. Named cultivars of Inchelium Red, Red Toch, New York White Neck, and Idaho Silverskin are suitable for zone 7. Softneck garlic also experience a period of vernalization, but it does not have to be as long nor as extreme as compared to hardneck garlic. Hardier than many of the softneck garlics, hardneck garlic it is an excellent choice for zone 6 and colder.
In Hardiness Zones 1 - 4: Plant hardneck garlic. Some of our favorite cultivars include: German Porcelain, Rosewood, Purple Glazer, Georgian Fire, Bogatyr, SPersian Star, Metechi, German Extra-Hardy, Georgian Crystal, and Romanian Red. Also, plant softneck garlic to determine how well it does in your region. Planting both hardneck and softneck will give you a better understanding of how each subspecies grows, appears, tastes and stores.
In Hardiness Zones 5 - 6: Plant hardneck garlic. If you are in a zone 6a or 6b, softneck garlic may do very well in your location. Also, plant softneck garlic to determine how well it does in your region. Planting both hardneck and softneck will give you a better understanding of how each subspecies grows, appears, tastes and stores.
In Hardiness Zones 7: This is considered a transitional zone. More than likely, softneck garlic will do better here compared to hardneck. Experiment and plant both softneck and hardneck, and label each. If you are able to expose hardneck seed garlic to a long period of cold temperatures prior to planting (vernalization) hardneck garlic may do okay. Place the seed garlic in a chest freezer or cold refrigerator (temperature set at 32 degrees Fahrenheit) for eight (8) weeks prior to planting.
In Hardiness Zones 8 - 10: Plant Softneck garlic. Zone 9a and Zone 9b is the same climate zone as the famous garlic-producing town of Gilroy, CA. Plant around late October/November and harvest in June or July. Hardneck may not grow well in your region. If you like to experiment and If you are able to expose hardneck seed garlic to a long period of cold temperatures prior to planting (vernalization) hardneck garlic may produce edible bulbs. Place the seed garlic in a chest freezer or cold refrigerator (temperature set at 32 degrees fahrenheit) for eight (8) weeks prior to planting.
Two most common mistakes garlic growers make are to plant the wrong type of garlic for their climate and to plant garlic at the wrong time. For many of us, the first time we shopped for seed garlic, we were overwhelmed by the large number of types there are to choose from. Unless you already grow garlic, you likely just know it from the cloves found in grocery stores.
Other common mistakes that have a negative impact on final bulb size include; 1. Allowing weeds to rob precious nutrients from the garlic plants; 2. Not providing garlic with enough nitrogen. Nitrogen is critical for plant growth and photosynthesis; 3. Waiting too long to harvest. Harvest when the bottom two or three leaves start to droop down and turn brown. Each leaf on the garlic plant corresponds to a thin, critical wrapper that protects the bulb. The more leaves that die off, the less protective covering the garlic bulb will have.
Don't Be Afraid to Experiment
In transitional zones, you may have success with hardneck and softneck garlic. You may wish to experiment for a few years, by planting and documenting your findings and harvest yields - for each subspecies. This scientific approach may help you determine if one subspecies does better than the other. No matter where you live if you’re not sure which to plant, one acceptable approach is to plant both softneck and hardneck subspecies. Trying several different cultivars of each subspecies - all at once - gives you a chance to find out which ones perform — and taste best to you. Communicate with other garlic growers in your area to determine what they have learned, and what grows best in your own climate and soil conditions. What is really important to understand is that Garlic is an adaptable plant, and it can take two or three years to adapt to a new environment.
Planting Bulbils instead of Cloves?
The million-dollar question is: If I plant Garlic Bulbils, instead of Garlic Cloves, will the garlic eventually acclimatize to my location?
Hardneck garlic propagation is often associated with the planting of garlic cloves. This 'seed garlic' is referred to as vegetative reproduction or cloning.
Another method for garlic propagation is growing garlic from bulbils. Bulbils are sometimes referred to as 'garlic seed'. There’s a big difference between ‘garlic seed’ and ‘seed garlic.’ Garlic cloves are separated from a garlic bulb and are similar in shape to segments in a citrus clementine. Bulbils, in comparison, are tiny, top-setting 'garlic seeds' that are produced at the tip of the garlic scape - which is referred to as Umbels. Umbels contain many bulbils. Hardneck garlic "bolt," which means that in the second stage of their growth, they produce a towering stalk (the curly scape) that carries at its tip, delicate, tiny flowers. It this garlic scape and the umbel at its tip are left to mature, they produce these tiny bulbils.
Softneck garlic (typically) does not produce a scape, and therefore softneck garlic does not produce these bulbis "garlic seed".
Bulbils are tiny, undivided bulbs produced in the scape of hardneck garlic. The bulbils are clones of the mother plant that can be planted to produce a replica of this parent. The amount of garlic seed produced depends on the variety. Some scapes contain less than 10 garlic plant bulbils - others may contain a 150 or more, depending upon the variety. Bulbil size ranges as well, from that of a grain of rice to the size of a sweet pea. Each tiny garlic bulbil is like a miniature garlic clove and is in effect a garlic seed.
Why plant garlic bulbils? There are several reasons to plant bulbils, either instead of or in addition to planting garlic cloves. Some garlic growers find they can build up their garlic stock using the bulbil method. Growers of garlic who are in a big hurry and wish to bring a full crop to market next year, plant garlic cloves instead of bulbils. The benefits to garlic growers include the dismissal of soil-born disease (such as white rot, nematodes, fungus, etc), exponential growth of seed stock, and gradual acclimatization of a hardneck garlic cultivar - to your climate and growing conditions. And, Bulbils can be eaten just like a clove.
If you want to grow garlic using these small pea-size bulbils, keep in mind that planting garlic seed is slightly different from planting garlic cloves. Garlic cloves, planted in the fall, will typically produce a harvestable crop the following summer. Garlic started with bulbils takes a bit longer. Start by planting garlic seeds in the fall at the same time as your regular garlic bulbs. They should be kept separate and labeled as such because they’ll take extra time to mature. Patience is key here. To harvest a full-size, fully mature garlic plant from bulbils can take two or more years. The tiny bulbil is much smaller than a garlic clove, and the plant will need a full year to get established in the soil and grow to the size of a garlic clove. The first year, it produces a single clove similar to a small golf ball, sometimes referred to as a garlic round (see chart below). Another year later, it’ll produce a full harvestable garlic bulb.
ADVANTAGES: The advantage of planting bulbils is that it helps growers increase planting stock in an economical way. An umbel can provide anywhere from 20 to 100+ bulbils for planting. In comparison, garlic bulbs provide 4 to 10 planting cloves. Another advantage of growing your garlic from bulbils is they provide you with a with a seed stock free of soil-borne diseases. Bulbils can be planted more densely as compared to planting cloves. Each year as they get bigger, you'll to provide them with more space. This give you time to scale up your operation. Planting bulbils is less expensive than growing garlic from cloves, but the big tradeoff is cost vs time. Another advantage here is that bulbils may be more resistant to soil-borne diseases and better adapted to your region.
DISADVANTAGES: The disadvantage of growing garlic from bulbils is that it generally takes 2-3 years of successive plantings to achieve good-sized bulbs.
It takes multiple years to go from bulbils to a full-sized bulb (2-5). You have to dig them up and replant them each year. They are small and delicate and do not compete with weeds well. Keep in mind that if you allow garlic to flower, it will focus energy on bulbil growth rather than bulb growth. This means that your bulbs will be smaller.
USDA Plant Hardiness Zone Map. Mapping by PRISM Climate Group, Oregon State University
Experiment with Vernalization
Although garlic is ideally planted in late fall, is it possible to grow and harvest garlic bulbs if you did not plant before winter? Most garlic growers that reside in a cold climate plant garlic in late fall because the plants require a natural dormant period that includes exposure to cold temperatures. This is known as vernalization. If garlic is planted a few weeks before a heavy frost or freeze, the cloves will produce string-like roots which help anchor the clove in the soil. There are garlic growers who have been trying to trick mother nature, by using a refrigerator or freezer to expose their garlic prior to planting.
If you intend to plant hardneck garlic varieties in the spring, the seed garlic - also known as a garlic clove - will need to be vernalized (exposed to cold temperatures for a period of time). The ideal temperature for this exposure is right around freezing (32° Fahrenheit or 0° Celsius). Vernalization can be achieved by storing garlic in a refrigerator. If possible, use a chest freezer set to a temperature right at freezing. Most chest freezers do not have an automatic defrost option - this is good news. Upright freezers typically do have an automatic defrost option which can rob moisture and life away from the garlic cloves. Using a refrigerator with an automatic defrost option can dehydrate garlic cloves if they are stored for long periods of time. Inspect the garlic often to make sure it does not mold, rot, or dry out. If you notice small, white, string-like roots or if the garlic begins to sprout, the temperature may need to be reduced.
Ideally, the seed garlic should be kept cold for a minimum of eight (8) weeks. Keeping the seed garlic cold for three-four months would be even better. Timing the vernalization with early planting can be a challenge. Ideally, the seed garlic should be planted in the ground as early as possible - after vernalization. In other words, get the seed garlic planted 2-3 inches into the soil as soon as the soil is thawed and workable. Hardneck garlic is cold-hardy and can withstand temperatures well below freezing. If the seed garlic is planted too late, it may not have enough time to form a robust plant which is needed for photosynthesis and bulb formation. The end result? The harvested bulbs will probably be small.
Without vernalization, most hardneck garlic will not form bulbs correctly, or at all. Often, non-vernalized cloves will produce a bulb with a single clove that looks similar to a small golf ball. These 'rounds' are still edible and can also be replanted in the fall. In the second or third year of replanting, they should produce a normal garlic bulb with many individual cloves - assuming the garlic is exposed to cold conditions before or after planting.
What are Planting Zones?
Planting zones are areas you can find on a Plant Hardiness Zone Map that show, generally, which plants are best suited to do well in a given area, or zone. In essence, plant hardiness zones have been used by growers for years to simply identify the plants that are most likely to survive the winter in their area. Being able to understand a hardiness zone map means you’ll have a starting point for making wise planting decisions.
Garlic grown in temperate regions such as the Pacific Northwest is responsive to temperature and photoperiod for proper clove and bulb formation (and subsequent seedstalk development of some varieties). Varieties adapted to southern latitudes, that bulb under the temperature and short day conditions common to those latitudes, may not bulb or segment properly in the Pacific Northwest.
With varieties such as California Early and California Late, a period of cold exposure is needed for proper bulbing and clove development. That cold treatment is thought to be about 6 to 8 weeks of mean temperatures below 40 F but may be considerably shorter with some strains. Garlic may be sensitive to a cold treatment range of between 32 and 50 F and is sensitive either during growth or while the cloves are in storage. Photoperiod interacts with temperature so that cloves held in cold storage will bulb quickly when planted in spring (increasing photoperiod) resulting in small bulbs.
Bulb and clove size is related to the amount of vegetative growth that takes place before bulb and clove initiation occurs. This determines optimum clove storage temperature, planting date and associated growing temperatures, and changing day length.
Cloves exposed to adequate cold treatment may have a reversion of vernalization under water stress and high temperatures (above 85 F) so normal bulbing does not occur. The longer the cold treatment, however, the more difficult it is to devernalize the plants. Also, plants that are growing rapidly with good soil moisture are less susceptible to devernalization.
Plant Garlic at the Right Time
Planting the garlic too early or too late can result in a poor garlic harvest. Most garlic grows best when planted in the fall. Some softneck garlic can flourish when planted in the spring, but hardnecks should, ideally, be planted in the fall in order to produce the largest, healthiest bulbs. In our experience most garlic growers make the mistake of planting too soon in the fall.
In Hardiness Zones 1 - 4 : garlic should be planted in late October or early November. Halloween is a good date to work around.
In Hardiness Zones 5, 6 and 7 : some growers plant their garlic in September or early October which is too early. Instead, plant seed garlic in late October, November or December. This prevents the clove from wasting energy on growing green shoots (tops), and allows the clove to generate roots to keep the clove anchored in the ground. A general rule for planting garlic in USDA zone 5, 6 and 7 is to have it in the ground by December 1st. That said, depending upon whether you reside in zone 7a or 7b, the timing might shift by a couple of weeks. The ultimate goal is to allow the clove to establish a robust root system before winter sets in. Most types of garlic need a cold period of around two months at freezing temperatures - to foster bulbing. If you have missed the opportunity to plant in the fall, you can attempt to trick the garlic, by storing the cloves in a cold area, such as the refrigerator, below 40 F. (4 C.). See "Experimenting with Vernalization" above.
In Hardiness Zones 8 - 10 : garlic should be planted in November or December after being exposed to cold conditions for at least 8 weeks.