This is not an easy Yes or No answer. Depending on the time of the year, most supermarket garlic is imported outside of Canada - primarily from China, Spain, and sometimes California. This imported garlic is available year-round in the supermarket. In some supermarkets, locally grown garlic is available between late August to about December. Locally grown means the garlic comes from nearby farms or within the province where the supermarket is located.
Some home gardeners have tried to plant garlic bought from their local supermarket or grocery store. The results are usually disappointing because the garlic produces small bulbs. More often than not, they do not sprout. But other home gardeners have had great success; these varying results are based on where and what garlic they have bought to plant.
If you can only buy planting garlic from your local supermarket, you should consider these three reasons before proceeding.
#1 Condition of Garlic
First, you have to determine if the garlic is local or imported. How do you tell the difference? Locally grown garlic will have its roots intact. Imported garlic will have its roots hulled out. CFIA (Canadian Food Inspection Agency) requires all imported garlic to have its roots hulled. This requirement prevents any soil-borne pathogens from being imported into the country. Locally grown garlic is not required to have the roots hulled.
The imported garlic tends to be in fairly poor condition when it finally makes it to the customer. The main reason is that they have been stored for a very long time (sometimes it can even be over a year) before it gets sold. It is also dry, and sometimes the garlic is sprayed with chemicals to prevent sprouting, bleached with chlorine to make it look white. In some cases, it may have been fumigated with methyl bromide - this is used primarily to kill bugs. According to the UN, methyl bromide is 60 times more dangerous than chlorine; it can cause respiratory and central nervous system damage. Local garlic is not pristine white (never been bleached); the wrappers tend to be stained, i.e. a light brown.
This makes imported garlic a low-quality seed stock for planting. The cloves planted typically produce weak plants struggling to grow bigger. Usually, it is a disappointing harvest; the bulbs produce small single cloved bulbs - known as rounds.
#2 Pests and Disease
Most imported garlic in supermarkets is grown primarily in China, sometimes Spain, or California. These regions have had issues with diseases, viruses and parasites (nematodes) that can potentially infect your soil. The actual garlic bulb may look great, but the microscopic organism can be dormant until the right conditions arise.
Once these pests are introduced into your soil, they can infect other plants, not just the garlic. It can take years, even decades, for some of these parasites and soil pathogens to be successfully eliminated.
This does not mean locally grown garlic has no issues; you will have to ask your Produce Manager, who is the local garlic grower that supplies the supermarket. The majority of local garlic growers are reputable farmers. Find out if they also sell seed garlic for planting. It is best to buy directly from them, i.e. at the farm gate, farmer's market, or online. Always ask the farmer how they plant and care for garlic, i.e. spray or use any chemicals.
# 3 Growing Region
China, Spain and California have much warmer climates than Canada. In Canada, our winters can be very long and very cold. This means that the imported garlic from supermarkets is not adapted to the local growing conditions. This is one of the main reasons the garlic performs poorly. Not choosing the right garlic to grow in your climate will significantly waste time and a colossal disappointment at harvest.
Most garlic from China is also softneck garlic, and the Canadian weather is not ideal for growing softneck garlic. It is always best to buy from a trusted garlic seed source that you know will grow in your area and climate. If you are determined to try growing supermarket-bought garlic, plant them in an area where you will not be growing garlic or any onion family. This is to prevent any issues with pests or diseases; also, you will still have a clean area to continue planting garlic.