A reader called the other day to talk about when to dig up the elephant garlic he planted last fall. The leaves were just starting to yellow, which is a sign that the time to harvest is drawing near.
In this climate, we generally harvest bulb alliums, which include slicing onions and garlics, from mid-June to early July, depending on the planting date. As my caller suspected, the tops of the plants offer the first clue for when to harvest. When the tops begin to die, this is an indication that the growth of the bulbs is slowing down.
The other test is simply to dig up a couple of the bulbs and see what you have. Even if they're not quite done, you won't be wasting the plants. Immature garlic and onions still can be chopped up and used in cooking.
For this reason, the harvest time for alliums is much easier to predict than for, say, melons. I can thump on the sides of a cantaloupe, give it the sniff test and still not be certain that it is ripe. Unfortunately, cutting one open, only to find that it still has a ways to go, will waste the melon. This is a gardener's Humpty Dumpty moment because there's no putting the melon back together again, and the fruit ends up on the compost pile.
Happily, we usually plant a lot of onion and garlic. Some gardeners have even been using immature bulb onions as green onions throughout the spring, so they have a pretty good idea of how far along the crop is.
Once harvest time has arrived, a bit of strategizing is required. Don't try to pull onions and garlic by their tops because most of the tops will come off. Remember that a fairly impressive root system is anchoring the bulb into the soil. Once the tops brown, they'll be no match for the roots.
The best way to lift bulb onions and garlic is to use a garden fork or pointed shovel. Slip the tool into the soil beneath the plant, making sure to go deep enough that you do not slice into the bulb - and lift. You'll be able to pull out the bulbs with the tops intact. Don't trim the tops at this point.
Avoid lifting your bulb alliums when the soil is wet. Your garlic and onions will be caked in mud and you'll have to scrub them, which will remove some of the outer skin. Digging when the soil is wet also harms the structure of the soil. At the same time, don't wait until the soil is so dry that it hardens. There's no sense in making the task more difficult than it needs to be.
Once you have your bulbs out of the ground, you'll need to cure them for storage. Lay the onions or garlic, with tops still on, outdoors for a couple of days until the outer, paperlike skins have dried. Some gardeners insist that onions and garlic be dried in direct sun. In my experience, that works well when temperatures are no higher than the mid-80s. When the heat has been intense, I have dried them on a covered porch.
At this point, you can wipe the dried dirt off the bulbs and cut off the tops. On onions, be sure to leave half an inch or so of the top attached to the onion. If you cut too close, the onion is prone to rot. Garlic does not seem to have this problem.
Bulb onions and garlic should be stored in a cool, airy place, out of direct sunlight. Storage life varies with the variety of allium, but both onions and garlic should be good for at least four months.
My caller asked whether he could reserve a portion of his elephant garlic crop to replant in the fall. This is the most economical way to proliferate garlic. The problem is that garlic has a tendency to sprout within a couple of months. If you can get the cloves back in the ground in September or early October, before the sprouting is too far along, you can "recycle" part of your crop. Otherwise, you'll have to start over with new bulbs.