Gardens are like experimental labs. And at the end of every planting season (we have two full planting seasons here in the central San Joaquin Valley), avid gardeners like to make notes and compare successes and failures with their fellow gardeners. I’d rate my successes with tomatoes this season at low 30 percent and credit/blame a big change in fertilization type and timing, longer and more frequent hot spells as well as insufficient water from a redesigned drip irrigation system. That’s my story …
Change in fertilization type and timing – My tomato crop this year was very disappointing. And since the tomatoes are in the front yard where neighbors can see the puny plants and small crop, also embarrassing. The plants were spindly and leggy with light green leaves. Flower set was good at first in April, but the first hot spell knocked off most of the blossoms.
This season I followed the newer UC Davis recommendations on fertilization, replacing a biweekly application of a half cup per plant of a commercial lower-nitrogen granular organic 4-5-3 tomato and vegetable food with a monthly application of several tablespoons of homemade compost.
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As a test of fertilizer potency, I changed back to the original commercial brand the third week of August. The tomatoes are now setting flowers very well with new darker green leaves appearing both at the end of the vine and from between the axils. We had hot weather at the end of August which normally slows new growth. It seems likely that the compost lacked sufficient nitrogen and phosphorus and that monthly feeding also did not provide enough nutrients.
Longer, more frequent hot spells – Yellow Flame, an early French tomato variety, did best since the fruit was on the vine before the worst heat, but the tomatoes were small, about half the normal size. Black Cherry was the first variety to set flowers and had good fruit set early but stopped setting flowers in mid-summer. Green Zebra and Costoluto Genovese varieties set a few flowers just as the high temperatures arrived in full force in late June but each produced just a few small, tough-skinned tomatoes.
In our climate, we need to select tomato varieties that either set fruit early (such as Early Girl and Yellow Flame), set copious amounts of flowers and fruit (such as Sungold and Green Grape cherry tomatoes) and that can tolerate weeks of high daytime and nighttime summer temperatures. Bush-type or determinate tomato varieties tend to set early and stop growth and production by late summer; indeterminate or vine-type tomatoes continue to grow and set fruit until the end of the season in late October. Vine-type tomatoes tend to be more vigorous than bush-type and tolerate heat better. I picked my favorites, rather than those best suited for the hot climate.
New drip emitters – This summer I replaced the plug-in, drip-only style emitters (two or three for each plant) with a type that emits a circular spray pattern that delivers water to a wider area. I should have placed at least two of the new emitters at each tomato plant to soak the entire root zone since the spray covered only about a six-inch circle. The drip irrigation system needed to be turned on for 20 minutes every day to keep the soil consistently moist during hot weather.
I’m already looking forward to next summer to put the lessons learned this season into practice.
Send Elinor Teague plant questions at email@example.com.