Garlic Vernalization
How to Vernalize Garlic:
The greatest obstacle to growing garlic in the south is the need for vernalization, otherwise known as winter cold exposure. Like some other herbs and plants, seed garlic requires exposure to cold to trigger germination. If you cannot expect temperatures below about 45 degrees F for a minimum of 6-10 weeks, you may need to artificially vernalize your garlic before planting. Fortunately, all you need is quality seed garlic, a home refrigerator, and a few weeks time before your zone’s planting date.
How Long to Vernalize
There have been various studies conducted on the best temperatures and lengths of times to chill garlic. A study from China, a major world producer of garlic, concluded that 40 degrees Fahrenheit for 20 days to be an optimum time. (Wu, 2015). However, a study from Trinidad and Tobago seems to indicate a longer vernalization period. This study found 42 days refrigeration at between 38 and 40 degrees Fahrenheit had the most potential for large final bulb size (Bridgemohan, 2017). A Brazilian study concluded 40 days as well (Resende, 2011).
The take-away from these studies indicates that if you find yourself short of time before planting, you may be able to get away with only three weeks refrigeration time. Eight weeks is a better option if time permits. If you are very deep south (Zones 9b or higher), the full eight weeks is probably necessary for best bulb development.
Sources 1. Fluegel, S. (2017). Southern Garlic Grower’s Guide. Grey Duck Garlic. https://www.greyduckgarlic.com/Southern-Garlic-Growers-Guide.html 2. Bridgemohan, D. Debisingh, G. (2017-2018). The Effect of Vernalization and Simulated ‘Cold’ Conditioning of Garlic under Tropical Conditions. www.cedaf.org.do>eventos>cfcs_2019> 3. Wu, C., Wang, M., Dong, Y. (2015). The Effect of plant age and vernalization on bolting, plant growth and enzyme activity of garlic. Science Direct.
Steps of Vernalization
1. Eight weeks before your planting date, place your seed garlic in a mesh or paper bag. Garlic can rot if stored in a sealed container, so make sure the bulbs can "breathe" somewhat.Use whole bulbs, not cloves. Cloves deteriorate quickly after being separated from the bulb. Place the garlic in the produce drawer of your refrigerator. Monitor to make sure your refrigerator does not dip below freezing. Frozen garlic will not germinate.
2. Leave the garlic in refrigeration for 6-8 weeks. Remove seed garlic from refrigeration when you are ready to plant. Garlic will sprout rapidly once removed from refrigeration, so it is important to time this with your planting date.
3. Plant your garlic as quickly as possible after removing from refrigeration.
Do I Need to Vernalize My Garlic?
Zones 2-7: No artificial vernalization (refrigeration) needed.
Zone 8: Upper regions should receive adequate chill hours to trigger germination. Lower regions may not. Experiment to find what works in your area. Sprouting and growth rate is generally better without artificial vernalization if there is at least minimal natural cold exposure. If you are not sure about your region, try refrigerating part of your seed before planting and planting the other half directly and see which does the best.
Zones 9-10: Vernalization will probably be required.
I hope this answers your questions! Grow your own beautiful garlic with our top-performing seed garlic! Garlic is a nutritious and delicious addition to every garden and kitchen. Free Shipping on Every Order!