Growing Together: June tomato to-do's

FARGO -- Would you eat a new fruit if someone told you it was poisonous? How about just a little taste to check out its flavor? No? I wouldn't either. Neither did our European ancestors when confronted with the new-fangled Central American fruit called the tomato.

For over 200 years it was grown in European gardens as an ornamental novelty. Because they're in the same large plant family as the notorious deadly nightshade, tomatoes were considered poisonous.

In the early 1800s someone finally ate one, lived to tell about it, and today the tomato is the most popular home-grown garden item.

Top tomato tips

-- Hopefully we all remembered to plant our tomatoes deeply, because they produce roots along the buried stem, building a larger root system capable of increased tomato production. If we didn't, hilling soil up around the plant's base helps compensate and makes the young plant less susceptible to wind whipping.

-- Tomato cages or stakes are best installed while plants are young, so developing growth can grow between cage slats, or be tied to stakes as plant size increases.

-- Determinate varieties are more bush-like and can be grown with or without cages or stakes. Indeterminate varieties continue season-long upward growth in vine-like fashion and are best supported.

-- Staking and caging help prevent foliage diseases by keeping plants off the ground, allowing increased air circulation

-- Fertilize tomato plants at transplant time or shortly after to stimulate rooting and growth. Water-soluble Miracle Gro-type fertilizers are easily absorbed and fast acting.

-- Granular tomato fertilizer can be cultivated shallowly into the surrounding soil following label for amounts. Although not as fast acting, it has a longer residual than water-soluble types.

-- Tomatoes respond well to water-soluble fertilizer applied every two weeks.

-- Mulching soil around tomato plants provides weed control and conserves moisture. Apply 2 to 3 inches of straw, dried grass clippings or wood fiber. Wait to apply mulch until soil has warmed to 75 degrees. If applied too early, mulch keeps soil too cool, and tomato plants need warm soil to grow and prosper. As of Tuesday, May 31, Fargo's soil temperature was 65 degrees. As a rule, mulch can be applied about mid-June most years.

-- Don't use clippings from lawns that have been weed-sprayed around tomatoes, because they can cause injury.

-- Avoid overhead sprinkling of tomato plants, because it can worsen foliage diseases by splashing fungi and bacteria from soil onto plants and spreading them from leaf to leaf. Water only the soil, or use soaker hoses.

-- Watering in the morning is better than evening water, because stems and foliage have a chance to dry before nightfall, lessening disease susceptibility.

-- Pollination and fruit set of tomatoes is temperature sensitive. If night temperature drops below 55 degrees when plants are flowering, pollination often fails. Blossoms drop off, and fruit fails to set, especially early in the season. To remedy this, spray early-season flowers with tomato blossom-setting spray, available at many garden centers. It's a naturally occurring plant hormone that sets tomatoes even in cool temperatures.

-- To combat foliage blight diseases that cause yellow, brown-spotted leaves, prevention is key. Leaves that are damaged remain affected, and won't revert to normal. Varieties vary in disease susceptibility.

-- Prevent diseases by keeping water off foliage, staking plants and mulching soil. During periods of high humidity, vegetable disease preventative fungicides containing chlorothalonil (check the fine-print active ingredient on the label) can be applied before symptoms occur, or at the very earliest signs.

-- Blossom end rot is a tomato disorder that isn't caused by disease organisms. The bottom of the fruit becomes sunken, brown-black and leathery. It's caused by the inability of the plant to access the available soil calcium because of fluctuating soil moisture, roots damaged by cultivation or soil that's too wet or too dry. It's worse on the first fruits of the season, and plants frequently work themselves out of the situation. To lessen chances of blossom end rot, avoid damaging roots with too-close cultivation and apply mulch to keep soil moisture more uniform. Research has shown calcium foliar sprays are ineffective.

More garden tasks

-- Some garden vegetables must be thinned out within the row, or they won't develop into useable produce. Carrot, beet, radish, spinach and lettuce seed often emerge thickly. Thin excess so the remaining seedlings are spaced about 1 inch apart. Gently pull or cut extras with scissors. Thinnings can be used in salads and sandwiches.

-- Large seeds like peas and beans are more easily spaced when planting, but if they emerged too thickly, thin seedlings to 1 or 2 inches apart.

-- Weeding between rows is easy with a tiller, hoe or wheeled cultivator.

-- Weeding within vegetable rows is more challenging. If weeds don't pull easily, a kitchen knife makes a precision tool for weeding close to plants.

Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler's Greenhouse in Fargo. Tune in to his weekly radio segment at noon Wednesdays on WDAY Radio 970. Readers can reach him at forumgrowingtogether@hotmail.com . He also blogs at http://growingtogether.areavoices.com .