Raising a crop of heirloom veggies isn't all that different from growing non-heirlooms. Like all vegetables, each heirloom plant requires sun, consistent moisture, and fertile, well-drained soil to grow and yield a healthy crop. Improving the existing soil by adding compost or a nutrient-rich garden soil like Miracle-Gro® Garden Soil for Vegetables & Herbs, and feeding plants regularly with a continuous-release fertilizer like Miracle-Gro® Shake ‘n Feed® Tomato, Fruit & Vegetable Plant Food will go a long way toward helping ensure your heirloom plants grow big and strong.
With a heirloom, though, it can also help to know where the plant originated. If it hails from Siberia, like the Black Prince heirloom tomato, then it will usually perform well in regions with cool summers. Plants like Blue Hubbard squash, which comes from the West Indies or South America, need a long growing season to achieve their full potential. In general, though, if you're following good growing practices, you'll get good results. To help you be as successful as possible, try these heirloom vegetable growing tips.
Many heirloom tomatoes are indeterminate vines that will continue to grow throughout the season, so they require support to grow their best and make fruit harder for slugs, pillbugs, and other ground-dwelling critters to reach. Tomatoes are also heavy feeders, and benefit from the addition of lots of compost and other organic matter to the soil. Some heirloom tomatoes lack disease resistance, so it's important to follow correct plant spacing to permit plenty of air circulation around plants. Also, consider adding mulch to help prevent soil from splashing onto lower leaves. Removing lower leaves (up to 12 inches from ground level) once plants are up and growing can also help.
Here are some additional tips
With dark varieties like Cherokee Purple or Black Krim, you may not actually see purple or black when fruit is ripe; instead, green tones will deepen toward a mahogany brown, and fruits will have a soft feel if you give them a (very gentle!) squeeze. In fact, fruit softness when ripe is one reason heirlooms aren't grown and shipped to grocery stores—they'd never make it intact.
Nearly ripe Yellow Pear tomatoes tend to split after heavy rains. If you know fruits are about ready and summer storms are in the forecast, pick them before the rain comes. They'll taste sweeter, too, as sugars will be more concentrated before the plants take up a lot of water.
As noted above, look to an heirloom variety's origins to help you know how — and whether — to grow it. Like the Black Prince variety from Russia, San Francisco Fog prefers cooler summers. Brandywine tomatoes are named for the Brandywine Creek in Chester County, Pennsylvania, while German Johnson is native to North Carolina and Virginia. These tomatoes all grow especially well in regions with conditions that are similar to those of their birthplaces.
Lacinato kalegoes by a host of names, including Dinosaur kale and Tuscan kale. Cabbageworms can make quick work of this green, so cover seedlings with floating row covers to exclude moths. If you do spy worms already on the undersides of the leaves, pick them off and squish them before covering. Or, surround Lacinato with sweet alyssum, and you'll likely host parasitic wasps that prey on cabbageworms. You'll savor the most tender leaves when you pick them under 24 inches long. As the hardest freezes and snow arrive in colder zones, continue to harvest, picking the leaves hiding beneath the frozen outer layer. These older leaves can be stringy, so remove center veins and chop them more finely than you would the tender center leaves.
Originating from the late 1800s, Lemon cucumber brings on a steady harvest all season long. In regions with frost-free winters, plant every few weeks to keep growing throughout the year. For round, ball-like fruits, trellis vines; this will prevent them from developing marks or flattened edges that typically occur when fruits rest on the ground. Pick these cucumbers when they're about 2 to 3 inches across, as they'll become seedy if they grow larger. Use this cucumber for an edible bowl for serving gazpacho, chicken salad, or chilled pea salad.
Tomatillo is a classic ingredient in Mexican cooking, and if you're trying to perfect salsa verde or yellow mole sauce, you want these in your garden. Plan to stake these heirloom plants, because they continue to grow and produce fruit until frost. Two things frequently prevent fruit set in tomatillos. First, in northern regions, flowers may appear before bees are fully active. In this case, patience will pay off. Second, a single plant will not set fruit; you need two plants for cross-pollination to occur. Harvest tomatillo fruits when they fill out the papery husks or husks start to split. Tomatillos produce a waxy gum to prevent dehydration; don't wash off this sticky coating at harvest, but use it to your advantage by storing ripe tomatillos like onions—in a hanging wire basket in a cool, dry spot.
Hale's Best Jumbo Cantaloupe
Like other cantaloupes, Hale's Best Jumbo craves warm soil enriched with plenty of organic matter prior to planting. In colder zones, warm soil by covering the growing area with black plastic about two weeks prior to planting. Usually, soil is warm enough about the time peonies are in full bloom. The right time to harvest this heirloom cantaloupe is what's known as "full slip," which simply means that you can pop the melon off the vine with a little tug. Pay attention to the stem that attaches the melon to the vine; you should notice some cracking in that stem right about the time the melon is ripe.
Dating to the 1840s, purple and white kohlrabi are small varieties that fit easily into today's modern gardens, where space is often at a premium. The secret to tasty kohlrabi is two-fold: timing and harvest size. First, plant as soon as all danger of frost has passed, because while kohlrabi is frost-sensitive, summer heat causes stems to turn woody. Keep plants mulched and soil moist as summer heat starts to arrive. Interplant with leeks, and harvest kohlrabi when the bulbs are small (under 3 inches); leeks will then have room to mature to full size. Pennsylvania Dutch colonists saved kohlrabi peelings, air drying them and storing them in glass jars until winter. Then, they would add boiling water to the peels to reconstitute them, and make a hearty vegetable broth base for soups.
Golden Scallop Pattypan Squash
The trick to truly enjoying this beautiful Pattypan summer squash is to harvest when squash is on the small side—2 to 3 inches is ideal. At this point, the flesh is succulent and nutty, and you won't have to peel it. Just wash, prep, and cook. Like all squashes, Pattypan needs rich, well-drained soil. Work plenty of compost into planting beds or containers. If you know where you'll be growing squash next year in your garden, add a layer of chopped leaves in the fall, then turn it into the soil when the new planting season arrives.
Charleston Gray Watermelon
Watermelon are heat-loving veggies, and Charleston Gray, developed in South Carolina, is no exception. Set out plants when soil has warmed and all danger of frost has passed. If it's the right time for planting beans, it's the right time for planting watermelons. Veteran watermelon growers agree that fertilizing vines early in the season is the key to beating cucumber beetles, a common pest. Young vines with a solid footing usually outgrow any beetle attacks. Harvest time is trickiest, because watermelons don't continue to ripen off the vine. Watch the tendril that's located immediately opposite the stem of each fruit; when that tendril turns brown and dries up, the watermelon is probably ready.