Kitchen Garden School: May

Kitchen Garden School: May

Welcome to the fifth lesson of Kitchen Garden School at Cornell Farm. It's finally starting to warm up a bit outside, which means that summer veg can start to go out into the garden. As we wrap up our final succession plantings of cool weather veggies and greens like lettuce, peas, and broccoli, we're making room for cucumbers, melons, beans, squash, zucchini, peppers, and — everyone's favorite — tomatoes. So, without further ado, let's learn about growing incredible tomatoes year-after-year!

Growing Beautiful, Tasty Tomatoes

Tomatoes are warm-season crops, and although we might often think of them being associated with Italian cuisine, they actually hail from the New World. In their native range, wild vines of Solanum lycopersicum grow as perennials, but when we cultivate them in cooler climates, we almost always treat them as annuals. These long-season crops can take a couple of months to begin producing fruit, which is why we grow them from starts, rather than waiting for seeds to germinate in the ground. As with other warm-season crops, these plants will do best if we wait until soil temperatures are steadily above 50ºF before planting them out in the garden, although as Cynthia explains in the video below, grafted tomatoes can often be planted out a little earlier thanks to a hardiness boost from their root stock.

Here's some useful terminology to know when shopping for tomatoes and knowing how to plant and care for the varieties you bring home:

  • Grafted vs. Conventional Tomatoes: Grafted tomatoes are an innovation that have only reached home growers in recent years, but they can be a great tool for gardeners in climates like ours that experience cool, wet springs. Essentially, a top cutting of a desirable variety (called a scion) is attached to the roots of a hardier variety (called a root stock). In the case of grafted tomatoes, this root stock offers added cold hardiness, disease resistance, and a more robust root system. In total, these qualities help to improve fruit set and extend your tomato season earlier in the spring and later into the fall, without changing the genetics or taste of the grafted variety. In contrast to conventional tomatoes, which are grown from seed, grafted tomatoes should not be planted "deep:" You want to keep the graft line (the scar where the two varieties were attached) above the soil surface so that the variety up-top doesn't form its own roots and negate the benefits imparted by the root stock.
  • Determinate vs. Indeterminate Tomatoes: Determinate (sometimes called "bush") tomatoes will yield the bulk of their harvest at once, and are often slightly smaller and don’t require substantial staking. Indeterminate tomatoes (sometimes called "pole" tomatoes), which includes most cherry and slicer type tomatoes, will produce a few fruits at a time indefinitely until they are knocked back by frost. These can grow much larger and require more staking, and they can also benefit from the kind of suckering (pruning some of the new growth) that Cynthia demonstrates in the video. In contrast, determinate tomatoes typically do not benefit from suckering.
  • What is an Heirloom Tomato? In simple terms, an heirloom tomato is an old variety that has been passed down for generations. To be considered a true heirloom, a tomato variety must be open-pollinated and genetically stable. In other words, it will come true from seeds when pollinated by other plants of the same variety in a population. This is in contrast to many commercially-available F1 hybrids, which are the children of a deliberate cross between two parent tomato varieties. They can be great garden plants, but just know they won't come true from seeds!

Because tomatoes are heavy feeders, the best practice for growing tomatoes involves rotating them between different areas of your garden. But a workaround for this is to simply amend the soil where you want to plant your tomatoes with granular gypsum. This is generally best done in the fall or winter to give the gypsum time to break down in the soil to make calcium available to the plants. Once your plants are growing happily, you can scratch in a bit of E.B. Stone Tomato and Vegetable Food around once per month to continue to feed your plants throughout the growing season. You will also want to keep up a steady schedule of deep watering, as tomatoes like it moist — but not soaking! As they start to set fruit, it is helpful to allow the plants to dry out more between waterings to encourage good fruit quality. And don't forget! Tomatoes will also require a bit of support, which can be as simple as providing a tomato cage or as complex as building scaffolding. The sky is the limit!

Armed with this knowledge, you should be well on your way to growing the best possible tomatoes, year-after-year.

Other Activities & Resources

Check out a few of the tasks you can undertake in the kitchen garden right now, along with "recommended reading."

  • Read the May chapter of The Maritime Pacific Northwest Gardening Guide from Tilth Alliance.
  • This month, there are several relevant readings scattered throughout Plant, Grow, Harvest, Repeat by Meg McAndrews Cowden. If you go to the index and look for "summer gardening," that should be a great start!
  • If you aren't feeling particularly inspired by traditional tomato cages, it might be worth doing a quick image search to see some of the methods other gardeners have come up with for staking their tomatoes. There are some really unique and aesthetically pleasing options out there; the sky's the limit!

      May Planting

      May is finally here, which means the first summer veg can officially go into the ground.

      • Once soil temperatures stabilize above 50ºF, starts of warm-season crops like tomatoes, peppers, zucchini, and squash can go into the ground!
      • While temperatures are still cool, it's a good idea to plant another succession of cool season crops to get you further into the spring. We still have a few options at the Farm this time of year, and will through most of May.
      • Large-seeded crops like beans can be direct-sown this time of year.
      • We're approaching the end of the window for planting seed potatoes, but it isn't too to get yours in the ground!
      • We have a fantastic selection of fruit trees, shrubs, and vines that have started to flower already. Look for apples, pears, persimmons, figs, blueberries, currants, raspberries, kiwis, pomegranates, and more.

      Connect With Us

      If you have questions about edible gardening or would like help selecting plants, our knowledgeable team is always happy to assist you in the Kitchen Garden Greenhouse. Cynthia often gives informal tours of our display beds, so feel free to stop by for a quick walk-around! For help from afar, you can reach out to Cynthia and our Kitchen Garden team directly at

      We are also excited to share that, for those wanting more individualized assistance with their kitchen gardens, Cynthia is also available for personalized 90-minute Garden Coaching Sessions held in your very own garden.