At this point in the summer, we should have a pretty good idea of what kind of a harvest we’re going to get from many of the plants in our vegetable garden. Take tomatoes, for instance. If the vegetation is green and lush and the plants are covered with blossoms and green fruit, we have cause for optimism.

But the components of our gardens that grow underground are a bit more difficult to read. In the case of onions, garlic and potatoes, we really can’t see what we’ve got until we start to dig. All the information we get along the way is telegraphed through the green we see above ground.

Most importantly, if we interpret what’s going on with the vegetation, we’ll know WHEN to dig. In theory we will avoid waiting too long, in which case the crop begins to rot, or digging too soon before the crop reaches maturity.

While new potatoes are delicious, they can be a huge disappointment if you had your heart set on full-sized spuds.

When the plants attached to onions, garlic and potatoes begin to die, it’s time to think about harvesting.

The shoots above my garlic started to yellow last week and I’m just waiting for the ground to dry out so that I can go in and dig. The most efficient way to get garlic heads out of the ground is to slide a shovel or potato fork underneath them and lift them out of the ground. If you try pulling them out of the ground, you’ll just pull the tops off many of the heads because garlic can have particularly sturdy roots.

When onion shoots start to yellow, bend them over to speed their demise. A few days later, when they are brown, you can dig the bulbs.

Potatoes also should be dug when their vegetation begins to wither and die. Take particular care when digging not to slice the potatoes with your shovel or fork. Begin digging out to one side of the row and try to loosen the soil around the plant without digging directly beneath it. At that point you can pull up the plant and the potatoes attached to it. You’ll have to feel around in the soil to find other potatoes left behind.

I have no clue how many potatoes I’m going to get this year. The plants look great but something ate the blossoms about three weeks ago. They are simply gone. I haven’t been able to find anything in my gardening manuals about how indispensable blossoms are to growing-fully formed potatoes but I know they are not there just for ornamentation. In short, this probably isn’t a favorable sign.

Once you dig up your garlic, you’ll need to air dry it for a couple of days in the shade. You usually can brush the dirt off the heads, but you may have to rinse them off before you set them out to dry. Be sure the outer skin of the heads has developed that paperlike texture before you store them.

Same thing with onions, except you’ll set them out directly in the sun for a day or two to allow them to develop a tougher skin so they can store longer. The most important thing about curing onions, however, is to leave the tops on until the bulbs have been sufficiently dried. If you cut the tops off too early, many of your bulbs will rot. Keep an eye on the bulbs to make sure that they aren’t burning up in the sun. If the temperatures are in the 90s, you might cure your onions in a dappled shade.

When the onion forms a tougher outer skin and the tops are dried close to the bulb, you can remove the top. Store onions in a cool, well-ventilated place.

Once you have your potatoes out of the ground, rinse them and lay them out to dry in a cool and dark place. They can be stored as soon as they are dry. It’s important to keep potatoes and garlic out of the light because both will sprout in storage.