All plants have different requirements for harvesting. Some vegetables will mature early enough to be harvested throughout the summer (ongoing harvest) while some will need to wait until August or early September to be big enough to harvest.
Leafy Greens
Leaf lettuces are ready to be harvested as soon as leaves begin to appear and they are about 4 inches long. Simply snip either single outer leaves or grab a bunch of them and cut them with shears or scissors an inch above the crown of the plant. If you cut into or below the crown, the plant will probably die, so be careful. Harvest before any seed stalks start growing in the middle of the plant otherwise the lettuce will be too bitter to eat. Some greens, like lettuce, will become bitter as the season progresses. Others, like kale, will get sweeter as the temperature cools.
Onions
In late summer, the leaves on the onion plants will start to flop over. This happens at the neck of the onion and it's sign that the plant has stopped growing and is ready for storage. If the weather is dry and there's no danger of frost, the plants can be gently pulled from the soil and laid right in the garden for a day or two. If the weather is wet or frost is possible, move the onions immediately into a protected spot. As the onions are curing, their necks will gradually wither and the papery skins will tighten around the bulbs. Once the necks are completely tight and dry, and the stems contain no moisture, you can use scissors to trim the roots off the bottom of each bulb.
Tip: Once harvested, spread the onions out in a single layer in a warm, dry and breezy envirnoment to allow the neck of the onion to dry.
Peas
When harvesting for pea pods, you can harvest when the pods are flat but at the right length for your variety of peas. It is also determined by what you want from the pea. If you prefer edible pods with developed seeds, allow more time before harvesting peas. When harvesting, pick peas with two hands. Secure the vine with one hand then pinch the stem of each pod and pull with the other hand. Don’t tug or jerk pods away; pea plants hang on to their support with thin tendrils so a heavy hand can dislodge the plant from its support.
Beans
Beans are ready to pick when the pods are still smooth, snap easily and the seeds haven’t formed bulges along the pod. Look for lean full beans that are firm to the touch. To harvest the bean, grasp the top of the bean and notice the little stem that connects the bean to the main vine. Break off the bean at the stem. You don’t want to damage the vine or plant, so be careful you don’t pull too hard on the bean before it’s truly been broken off.
Tip: Avoid waiting too long to pick when the seeds inside are bulging and the bean has become stringy.
Beets
To determine whether beets are ready to be harvested, clear away some of the mulch or soil around the top of your beets and look for crowns protruding above the soil line. If you can see an inch or two sticking out above the soil, it’s a safe bet that they are ready for pulling. If your roots don’t look quite ready and a frost is in the forecast, don’t worry! Beets are a cool weather crop, and a light frost or two can actually sweeten their flavor. Just make sure to dig them up before the ground freezes. When you have decided it’s time to harvest, use a garden fork or knife to gently loosen the soil around each plant, being careful not to accidentally slice into any of the roots. Once the soil is loose, grab hold of the green tops and lift carefully, while simultaneously prying the soil underneath with a hand fork or garden knife.
Tip: Beet greens can be harvested to eat as a leafy green while the bulb is still growing by snipping 1-2 leaves off each beet.
Broccoli
Broccoli is ready to be harvested when the head is 4-7 inches wide and it is deep green in colour. When your broccoli head is ready to harvest, use a sharp knife and cut the head of the broccoli off the plant. Cut the broccoli head stem 5 inches or more below the head, then remove the head off with a swift cut. Try to avoid sawing at the stem as this may cause unnecessary damage to the plant and ruin your chances for side harvesting later.
Tip: After you have harvested the main head, you can continue to harvest the side shoots from the broccoli which will grow like tiny heads to the side of where the main head was. By looking at the size of the florets, you can tell when these side shoots are ready for harvest. Simply cut them off as they become ready.
Cabbage
Cabbage is ready to harvest when the heads are solid. Give it a squeeze. If you still feel some softness, you should wait a bit. Heads may be large or small when ready. When the cabbage is ready for harvesting, you have two options: 1. Grab the base of a cabbage head and pull. In loose soil, you’ll bring up the entire plant, root and all. 2. Using a very sharp knife, cut the cabbage head off, leaving a few inches of the stem and some of the large, floppy leaves intact and leaving the root in the ground.
Carrots
The size at maturity depends on the variety but carrots should be firm and bright in colour. Most varieties are ready to harvest when the shoulders are 1/2 to 3/4 inch in diameter, but again, there is much variation depending on the variety. To harvest, loosen soil around the carrot with a spade or trowel before pulling up from the greens; this will help avoid breaking the greens off from the carrot roots. Carrots mature roughly around the same time, but you don't have to harvest them all at once.
Tip: Baby carrots can be harvested when thinning the beds.
Cauliflower
Ready to harvest when the head is 6-12 inches in diameter, firm, compact and white. When you’re ready to harvest the cauliflower head, cut it from the main stem but leave a few of the outer leaves attached to help protect the head and prolong its overall quality until ready to eat. Be sure to handle the head carefully as it can bruise rather easily.
Celery
Ready to harvest when the stalks are 6 inches long from the ground to the first leaf. Harvesting celery is done by cutting the stalks below where they are joined together.
Tip: Picking celery can include the harvest of the leaves for use as a flavoring in soups and stews.
Cucumbers
Ready to pick when they’re about 7-9 inches long and medium to dark green and firm. Use garden shears or pruners when harvesting ripe cucumbers. This will prevent injury to the vine by twisting or pulling. Cut the stem ¼ inch above the fruit.
Herbs
Ready to be picked as soon as the leaves are large enough to be worth picking. To havest leafy annual herbs, such as basil, pinch at the tips of the stems, gathering several leaves at a time. Longer stemmed herbs, such as cilantro, parsley, lavender, and rosemary, should be cut near the base of the branch. Leafy perennial herbs, such oregano, thyme, sage, and tarragon, are to be harvested by the stem in sprigs.
Tip: Only harvest 1/3 of the plant at a time, otherwise the plan will start to flower, and the herbs will turn bitter.
Potatoes
Ready to harvest when the leaves start to wilt after the first frost. After deciding when to dig up potatoes, dig up a “test” hill for maturity. The skins of mature potatoes are thick and firmly attached to the flesh. If the skins are thin and rub off easily, your potatoes are still to new and should be left in the ground for a few more days. To harvest, pull up the plants and gently dig for the potatoes underneath.
Tip: Stop watering the potatoes at least 2 weeks before harvest to allow the potatoes to grow their skin for winter storage.
Radishes
A good way to tell if radishes are ready to be harvested is to simply pull one from the soil. If the soil is particularly crusted or hard, use a garden fork or trowel to gently lift the root from the soil. If the roots are about 1 inch in diameter, they are ready to be harvested. Cut the tops and tail root from the radishes, wash them, and they are ready to eat!
Squash (including zucchini)
Depending on the type of squash, expect 1-6 squashes per plant. Summer squash and zucchini are harvested the moment they reach a usable size. Just cut them free from the plant- don’t pull on them. A zucchini can be eaten at 6 inches or they can keep growing to upwards of 2 feet long.
Tomatoes
Once the tomato turns dark red, cut it off of the vine with scissors, leaving a short stem attached. This is to help the tomatoes stay fresh, and not mould.
Turnips
Ready to harvest when the shoulders of the bulb are protruding the soil. Ideally the root will be about 2-3 inches in diameter or the size of a baseball. Your turnip harvest should all be pulled before a frost or the root may crack and rot in the soil.
Tip: Turnip greens are nutritious, versatile vegetables. You can harvest them from any variety of turnip but this will impede production of the roots. Only cut the greens once if you want a turnip harvest of roots.