Seasonal Gardening: Yield-Boosting for Vegetable Seeds, Harvesting Spinach, and Tree Roots

News on special yield-boosting crop treatments and research briefs on when to harvest spinach, exposed tree roots, watering sweet potatoes, and adding nutrients to grass.
By Greg and Pat Williams
March/April 1986
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Researchers at Tokyo University report daily fluctuations in the mineral content of spinach leaves. Nitrogen, phosphorus, potassium, and magnesium levels were found to start dropping after sunrise, hit a minimum in late afternoon, then increase to a maximum at dawn.

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Greg and Pat Williams, expert gardeners, share tips and ways to utilize new gardening research for seasonal gardening. 

Seasonal Gardening

Special Yield-Boosting Treatments

Recently, we've collected quite a few ideas concerning doing "strange" things to vegetable seeds and seedlings to try to increase yields. All of these suggestions are based on research reports from professional horticulturists—but that's no guarantee that they'll work for you. In fact, we're hoping that readers of THE MOTHER EARTH NEWS will experiment with these techniques and let us know their results! (Just remember to grow a few untreated "control" plants to compare to your experimental ones.)

Russian scientists have seen yield increases of up to 88% after soaking the seeds of some tomato varieties in a 6.5 % solution of skimmed milk. Another tomato seed treatment (reported by Egyptian researchers) for boosting yields is to heat air-dried seeds for two hours at 140 degrees Fahrenheit: Apparently, the heat changes the proportions of natural growth regulators in the plants.

A Netherlands experimenter has found that thinning peppers to leave only a few fruits at the initial fruit-setting stage increases yields and average fruit size. Canadian researchers reported large yield increases for cowpeas that were "beheaded" between the fourth and fifth leaves on the main stem when the fifth leaf reached full size. The decapitation also made the plants more compact. (Might this technique work with soybeans or green beans?) Similarly, Cornell University horticulturists found that removing the growing tip from a tomato plant when it has four or five leaves delays first flowering two to five days, but then creates simultaneous flowering of several branch clusters and hence higher "second-earliest" yields.

Research indicates that if you're growing your own transplants, you should not skimp on container size: Many vegetables produce larger yields when started in roomier pots. And several studies have shown beneficial results from watering just-transplanted vegetables with seaweed extracts . . . which seem to help minimize transplanting shock.

Plant growth regulators added to seeds can also sometimes have positive effects. Researchers in India reported that soaking onion seeds in a solution of NAAm, or naphthaleneacetamide, at a concentration of 20 parts per million for eight hours prior to planting boosted onion yields by nearly 60%. Soaking the seeds in a gibberellic acid solution (7.5 parts per million) increased yields by about 20%.

There seems to be no end to the experiments you can do with seeds and seedlings!

Seasonal Gardening Research Briefs

Harvest spinach at dawn? Researchers at Tokyo University report daily fluctuations in the mineral content of spinach leaves. Nitrogen, phosphorus, potassium, and magnesium levels were found to start dropping after sunrise, hit a minimum in late afternoon, then increase to a maximum at dawn. So if you want the most minerals possible from your spinach, you'll have to get up early!

Rx for exposed tree roots. Recent experiments in England-on birch and ash trees-suggest that water losses from bare-rooted trees can be excessive if the roots are left exposed for a couple of hours. Drying for a few minutes, though, is unlikely to be damaging, so don't worry about keeping the roots damp every second. What about roots that arrive in the mail already dry? The English research suggests that soaking can be beneficial — at least in some instances — and does no harm in any case.

Water your lawn trimmer line. A professional lawn care company has found that the nylon line used in rotary lawn trimmers lasts about twice as long if it's stored in water before being put on the trimmers. (The water makes the line less brittle.) The treatment is supposed to be most effective when temperatures are high.

Don't overwater the sweet potatoes. If you grow sweet potatoes in a dry climate, cut back on irrigation for one month, beginning about a month after planting. According to Tennessee State University researchers, drought stress during this period results in reduced top growth and bigger root yields. Drought stress imposed late in the season, though, reduces root yields.

Green up your grass with iron. Horticulturists at the University of Illinois, Urbana-Champaign have found that foliar sprays of iron sulfate or iron chelate can enhance the color of Kentucky bluegrass without overstimulating growth the way added nitrogen does. An application of one pound iron per acre (about one-third ounce per 1,000 square feet) is recommended. Enhanced color lasts from a few weeks in cool wet weather to several months in cool dry weather.

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