When Do I Harvest?
By Steve Reiners, Professor and Chair, Horticulture Section, Cornell University, Cornell AgriTech. This is part of a series of columns that he wrote about vegetable gardening during the pandemic that ran Spring-Summer 2020. Read more articles from 2020 | Read later articles in this series.
July 31, 2020
A question that often comes up for new gardeners is when to harvest a particular vegetable. For some things it’s easy. Tomatoes change from green to red (or yellow, pink or purple) when they reach their peak. And even if you pick them too early, they continue ripening on your kitchen counter – but never in the refrigerator!
But other vegetables are not so easy. You only have one shot to get melons at their peak ripeness. Their flavor and texture only goes downhill after harvest. Root crops like carrots, potatoes and garlic are hidden underground so you need to look for above ground cues. Some like peppers can be harvested while green. But if you want sweeter, hotter or more complex flavors, it’s best to wait until they turn color.
I’m seeing this in my garden this week. The hot summer has pushed my onions along quite quickly. I have harvested one or two green onions as needed for cooking for the last two months, but now they all seem ready. How do I know? The tops are starting to yellow and fall over.
Once about three quarters of the onion tops fall over, gently push down the rest of the tops. Be delicate as your goal is to keep the bulb attached to the top. After a couple of days, loosen the soil and gently pull the onions out, again keeping the tops attached, and lay them on the soil surface to “cure”.
Rather than let the onions cure in your garden you could also put them in a warm, dry and airy place like a garage or covered porch. Frequent rains can cause problems with proper curing.
Curing allows the onions to slowly dry and the necks above the bulbs to close and seal, minimizing the chance of rots so they’ll keep longer in storage. After 10 days, snip off the tops and place the bulbs in a cool, dry location. You can have onions for months if you do this correctly.
Melons & squash
How about melons? For muskmelons or cantaloupes, it’s easy. As the fruit ripens, the attached stem “slips” off the vine. This usually happens as the fruit’s color changes from light green to a greenish yellow. At the slip stage, it’s at peak flavor and ready to eat or refrigerate. Remember we say slip off the vine and not pull hard. Be patient.
Watermelons are more challenging. There are subtle changes to look for. First, the ground spot (the side laying on the ground) will change color from white to a creamy yellow. Look for the small leaf and curly tendril nearest the fruit to brown and dry. From my experience, even after you notice these changes wait a couple of days for peak ripeness.
Some veggies are good anytime. Cucumbers and zucchini can be harvested at any stage. The smaller fruit have smaller seeds and better texture. Winter squash that you plan on storing in the fall needs to pass the “thumbnail” test. When your fingernail can’t easily pierce the skin, it’s ready.
Other vegetables & greens
People often ask where colored peppers come from, not realizing that the green bell pepper we’re familiar with is actually the immature stage. Like a tomato, if left on the plant longer it will ripen to its final color, which depends on the variety. The flavor is better after they color up. But if you delay harvest too long they are more likely to rot. That’s why colored peppers are more expensive.
Leafy crops are often better when immature, especially when grown in the heat of the summer. But as the cooler fall weather arrives, quite the reverse is true. Crops like kale and spinach get more flavorful after frost.
Carrots and beets can be harvested anytime but their flavor is also improved as the weather turns cooler. Potatoes too can be harvested when the plants first flower for small, “new” potatoes. But wait until the plants yellow and brown to get the largest spuds and the biggest yields.
This week in the garden
Plan for fall. Root crops like carrots, beets and turnips can be planted through August 5. This is the weekend to plant broccoli and cauliflower transplants. Plant leaf, Bibb, and romaine lettuce – until August 15. (Avoid heading lettuce. They don’t do well in our climate.) September 1 is your deadline for planting Swiss chard and spinach. You can even plant some spinach varieties like Vienna as late as September 15 and overwinter the crop to get fresh greens early in spring. Plant garlic -- your last fall-planted crop in October. More on that in a later column.