Soil Moisture Before Harvest
Dry soil conditions is a natural signal to garlic that it's growth and bulb filling period is coming to a close. This means that you should stop watering your garlic crop two to three weeks before harvesting the bulbs.
In regions of high rainfall where garlic often continues to get moisture right up until harvest, maturity may take a little longer, and the garlic may need more drying post-harvest while curing.
Too much moisture at the time of harvest can also increase the chances of root or bulb rot and can expose the cloves if the bulb wrappers have broken down. This is worse on heavy or saturated soils and not as much of a problem in sandy soils.
On our farm, the weather tends to be on the dry side once harvest comes along, although we do get the odd heavy downpour that can make things very wet. This means that we try to cut back on watering three weeks before harvest begins. This works well because we have heavy clay soils that can hold onto moisture for many weeks.
Harvesting garlic at the right time is a bit of an art and will depend on a few things. Garlic continues to grow as long as there are still green leaves on the plant. That means you want to leave the garlic growing for as long as possible to maximize the size of the bulbs without have the wrappers begin to deteriorate.
For most hardneck garlic varieties, it is recommended that the plants are dug up when half the leaves are still green (upper portion), and half are brown (lower portion) or when there are still about 4 to 6 green leaves on the plant. The number of garlic leaves corresponds to the number of bulb wrapper layers, so as the leaves turn brown and die, the corresponding bulb wrappers begin to deteriorate.
For example, if you have six green leaves when a plant is harvested, you should have six layers of bulb wrappers protecting the cloves and allowing for cleaning/handling of the garlic. If you have no green leaves, the chances are that your cloves will be exposed, unprotected and have begun to deteriorate.
Most softneck garlic varieties in Canada tend to mature more quickly than hardnecks (usually about ten days earlier). The tops can transition from green to mostly brown in a few short days. This tendency to mature quickly is often made worse by hot weather.
If left in the ground too long, the softneck bulb wrappers can split open and cause deterioration issues. These varieties need to be monitored closely and should be harvested at the first sign that the first lower leaves (2 or 3) are beginning to brown or signs that the bulb wrappers are starting to deteriorate.
On our farm, we tend to harvest all our garlic on the earlier side, with at least 1/2 the leaves still green for hardnecks and at least 2/3 still green for softnecks. Due to our heavier soils, we need the wrappers to be strong and healthy in order to handle the extra cleaning, as well as any excess moisture issues that might arise around harvest time.
Digging & Harvesting
In gardens and small areas, a pitchfork or broadfork can be used to loosen the soil under the garlic before pulling. In market gardens or commercial fields, an undercutter bar is pulled behind a tractor and run under the garlic bulbs to loosen the roots and make harvesting easy.
It is very important to be careful in order not to damage the bulbs while doing this task. Any nicks or bruises can be a route for pathogens like rot or mould and can also leave the garlic unmarketable or unable to store properly.
Garlic plants harvested and laid out on the ground to dry for several days before being brought inside to complete the drying process.
Most growers bring their garlic directly into a sheltered area immediately after harvest, however, some growers leave their garlic in the field for several days. This can help speed up the drying process and generally results in very clean bulbs.
If garlic is left in the field or garden and hot weather is expected, the garlic can be placed in rows with the leaves of one row covering the bulbs of the next row, to protect them from the sun. This way the leaves will dry, but the bulbs will be protected.
On our farm, we generally run an undercutter bar under the garlic to loosen them first. If the conditions are dry, we sometimes leave the garlic in the ground after undercutting for a day or so in order to kick start the drying process. Leaving them in the ground longer however can sometimes make cleaning them a little bit harder if it rains, so it depends on weather conditions.
We also often leave the garlic laying out in the field for 2 or 3 days if the weather permits. This helps to dry off most of the soil and begins the curing process. We prefer to do as much of the cleaning in the field when conditions are favourable.