Growing tomatoes in the Maritime Northwest can be a challenge, even with the warmer summer temperatures of the past few years. Tropical plants native to South America, tomatoes struggle with our more temperate, though sunny and dry, summers. For the coastal climate of Fidalgo Island, with late afternoon fogs that roll in each day and cool overnight temperatures, the warmth-loving plants find it difficult to set flowers and fully ripen. Even more inland garden sites can dip below 50 degrees at night, which is the critical threshold for successful tomato pollination.
Protection is what is needed. A grow tunnel of nursery-quality plastic, or a standard greenhouse, offers the needed heat units as well as some protection from diseases spread by wind or rain-dampened foliage. In addition, covering the soil beds with a layer of black plastic warms the earth, conserves moisture, and prevents soil-borne fungal diseases.
But there is a caveat. The use of non-composting, polluting plastics in an organic, sustainable garden is a problem for all those concerned about climate change and the health of our local environment. The real issue is that plastic is cheaper and more convenient to use than permanent greenhouse glass. The best rationalization is to responsibly dispose of all used plastics as best one can. Black plastic nursery pots can be recycled. High quality, UV-resistant, translucent sheeting for hoop houses will last up to 5 years. Black plastic used as a ground cover is problematic, however. Compostable newspapers can be used for some of the same effect, if laid down in very thick layers, using only the news sections not the colored ads on slick paper. Floating polyethylene row cover material will last for many seasons, if a heavy-duty grade is used and one is careful to avoid tears. But winds and sun take their toll on all petrochemical products. It is the price one pays for ease of use and low cost, a too-familiar refrain for many things. A glass greenhouse will always be the ideal solution, but may not be feasible for most gardeners.
May is tomato plant sale month, featuring varieties that will do well in our area, as well as many heirlooms types that require extra heat. Choose a selection of varieties, ranging from those bred specifically for the Northwest, to new cold-hardy recent imports from Eastern Europe, or standard beefsteak types that thrive in the heat and humidity of the Midwest. A favorite of mine is the Italian Oxheart, Cuore Di Bue, shaped like large plums, offering luscious taste, especially when served with slices of mozzarella, and topped with olive oil and basil leaves. Bottom line: they all will require generous heat to fully ripen, whether it is the Green Zebra or the Big Boy. Ripe tomatoes are the most wanted of all summer vegetables for the home gardener these days, so extra care is needed to fully satisfy our love of the red orbs.
Unless you grow your own seedlings, buy starts early in the season to get healthy, bushy plants that have not gotten too leggy yet or developed blossoms, a sign of early stress. Pinch off any flowers before transplanting to restart bud growth and eventually develop a much greater number of flowers. For large root development I buy tomato starts only in half-gallon pots. If root-bound, carefully untangle the roots before planting.
To plant tomatoes lay out a 3-to-4-foot wide bed of heaped-up healthy soil inside a hoop house or grow tunnel; cover with the black plastic (or newspapers) for several days to warm up the dirt. Make 8-to-10-inch wide holes in the center of the bed every three feet. Dig a transplant hole that is 8 to 10 inches deep; add a handful of organic all-round vegetable fertilizer and a bit of dolomite lime, and mix in well.
Remove all the lower branches of the plant, leaving only the three topmost branches. Add a few cups of water into the hole; bury the root ball at a 45-degree angle in one, slightly deepened end of the hole. Lay the pruned main stem at an angle onto a gradually upward sloped bed of soil; cover the bare stem with soil. Leave the three leafy stems exposed and gently bend them to vertical.
The pruned, below-ground stem will sprout additional side-roots and make a larger, sturdier plant; the shallow, angled hole will be much warmer than a deeper hole dug straight down. Gently firm the topsoil around the transplant, forming an 8-to-10-inch wide shallow crater. Place a small stake by the tomato top and twist-tie the stem to it for initial support.
Just beyond the exposed hole, under the bed covering, hill up an inch-high circular berm of topsoil, with the transplant at the center. The crater will serve as a small retention pond, keeping the water directly above the roots. Place the half-gallon black plastic nursery pot (with drainage holes) on the exposed soil next to the tomato stem on a side nearest to a path; put a few small stones in to weight the pot down.
From now on instead of watering either directly onto bare soil or onto the plant from above, water gently into the pot, to avoid splashing droplets containing soil onto the leaves, which could spread spores of the dreaded late blight disease. As the vines fill out, trim the bottommost leaves growing over the pot to allow access for your watering hose or can. Mid-season liquid fertilizer treatments can also go directly into the watering pot. Think of it as a tomato IV-stent, feeding the roots directly. (Note: a drip irrigation system could also be used as an alternative watering system.)
Water the plants every two to three days; hot weather requires daily doses. Install a thermometer since hoop houses get hot fast on warm sunny days, climbing easily above 90 degrees by mid-morning. Do not fry your tomatoes! Maintain good ventilation.
At night, to guarantee fruit set on the blossoms, keep the temperature above 50 degrees by closing doors, windows, or end-panels. Open up early in the morning to dry off the overnight condensation that forms on the ceiling, to prevent the moisture from dripping onto the leaves.
Lastly, to aid pollination, when the plants are covered with blossoms, every few days gently shake the tomato cage or whatever support used, to get the pollen distributed into the air of your tomato temple. Tomatoes are a full-time job.
Determinate or Indeterminate
Bush type, determinate tomatoes grow to a set height, not needing as much support; they fruit earlier and bear heavily initially, but soon decrease in yield and flavor. They are good for that first ripe tomato of the season; Oregon Spring is a standard. Indeterminate types are ever-climbing vines that will push against the top of the hoop house by mid-August. Tall cages with extra string around the edges are a necessity; prune to one main stem with one or two side stems to keep the plants open to the air and sun. They have later, extended harvests, with better tasting fruit.
For sauces and paste, the Roma types have more flesh and less juice than round, slicing tomatoes. The San Marzano yields large, pepper-shaped fruit well into September. Cherry tomatoes, whether yellow or red, are the most prolific and easiest to grow: Sun Gold or Sweet Million are indeterminate types that will keep your salads supplied all summer long. My favorite cherry variety is a German type, with clusters of grape-shaped tomatoes.
Fresh tomatoes deserve to be eaten with fresh basil. Don’t wait until June to put in basil starts. Transplant basil into your hoop house at the same time as your tomato starts; the basil will appreciate the early heat and be ready for that first ripe tomato. Keep the basil free of any flowers or seed heads and it will last all summer long.
Peter Heffelfinger, a Washington State University master gardener, has gardened organically on Fidalgo Island and the Skagit Flats for over 40 years. He has given workshops in year-round gardening for Transition Fidalgo/Eat Your Yard, Christianson’s Nursery, and at the Washington State University County Extension Service. He is a Salish Sea Steward, working on the invasive green crab survey.