Master Gardener: Time to plant some garlic

By Jerry Vitalis, Chisago County Master Gardener

The Chisago County Master Gardeners recently offered a class on growing garlic in the home garden that was presented by Carl Rosen, Soil Scientist at the University of Minnesota.   Carl became interested in growing garlic after being asked how best to fertilize the soil for a good garlic crop.  That was 15 years ago and in his own admission, he is addicted to growing garlic.   The class was very well attend, which is a testament to the interest there is out there for adding this member of the onion family to the home garden.
Late September to the first two weeks of October is the time to plant garlic cloves.  By this time we’ve already had the first frost of the season.  Garlic cloves need a chilling process to develop adequate bulbing.  Your soil should be a well-drained loam that is high in organic matter with a PH of 6-7.   The cloves should be planted flat end down at a depth of 1-2 inches and 4-6 inches apart in 2-4 row beds.  Space beds apart 2-3 feet.  There are many good sources for cloves.

One of them is not the garlic you buy in the grocery store, as that garlic is not well adapted to Minnesota growing conditions. You can also plant garlic in the spring, but it’s a much more complicated process that involves starting the cloves indoors in late February or March.

The most critical stage in garlic bulb development is in May and June when good irrigation of this shallow rooted plant is essential.  About 1 ½ to 2 inches of water a week should be sufficient but then stop watering two weeks before harvest.  In general, garlic harvest in Minnesota usually extends from the second week of July through the first week in August in the northern half of the state and late June through mid-July in the southern half. Different varieties will mature at different times.  Harvesting too late will force the cloves to pop out of the skins, making them susceptible to disease and resulting in unmarketable bulbs. There are a couple of procedures that can be used to determine when to harvest.

By late June to mid-July the lower leaves will start to brown and harvest is usually optimum when half or slightly more than half of the leaves remain green. Make sure to pull a few bulbs and cut them in half; if the cloves fill the skins, then the bulbs are ready to harvest.

This year was a very different year for growing garlic in that some crops were literally ruined from a disease called Aster Yellows and it was the first time ever in the U.S. that Aster Yellows has infected garlic.  Most likely the reason is that the spring of 2012 was quite warm and garlic was one of the only plants green at the time, making it a perfect target for the leafhoppers that transfer the disease from plant to plant.  Normally leafhoppers don’t feed on garlic, but for the reason mentioned, this was an early source of food for them.

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