So it’s becoming clear that both soil temperature and air temperature are critical for growing giant tomatoes. Let’s briefly consider these in turn.
It’s my impression that the vast majority of the world’s elite giant tomato growers raise their tomatoes in a soil medium with a high proportion of organic material and using all, or at least mostly organic methods. Perhaps the key to successful growing in soil is the presence of endomycorrhizal fungi. These very delicate symbiotic microorganisms establish an intimate relationship with the tomato root system. The tomato plant provides the fungi with carbohydrates, while the fungi greatly increase the nutrient and water uptake by the plant. The fungi require a good supply of organic matter to thrive and probably can barely survive, if at all in soilless media.
These fungi, along with other beneficial fungi, bacteria and other tiny critters in the soil, have an ideal temperature range within which they grow, reproduce and metabolize while making nutrients available for plant roots. At temperatures above or below this ideal range, this soil microfauna just cannot perform at optimal level.
So what is this optimal range? Regrettably I have neither conducted the research myself nor reviewed the primary scientific literature on this point. Based upon anecdotal evidence, some light reading and discussion with other growers, I’m estimating this ideal temperature to be in the range of 60-75° F. Likewise I’m making assumptions when I suggest that soil temperatures at 4″ deep lag behind average air temperatures by 2-3 weeks.
Unfortunately, I’m not working under a research grant and have had neither the time nor the resources to keep track of soil or air temperatures on a consistent basis
Anyone who has raised tomatoes during the heat of Summer knows how stressed the plants can get: blossom drop, leaf curl, excessive transpiration, wilting, blossom end rot, sunscald on fruits and poor growth. From the perspective of trying to grow giant tomatoes, this is what I have found after three years of attempting to grow ’em BIG during the heat of summer in the high desert of the Salt Lake Valley.
Given the right genetics, soil preparation, adequate water, proper pruning and a BIG megabloom, my tomatoes start to slow their growth after about 36 days from blossom set, start ripening by 40 days, and need to be picked by 45 days to achieve maximum density (at least 50% ripe) and weight. That dreaded first pink blush in the middle of a hot summer is a too-oft-repeated sign that, once again, I’m VERY far from a record-sized tomato.
Yet there are a number of growers who consistently raise 4-5+ lb. tomatoes. At the risk of ruffling feathers by presenting an incomplete list, I’ll refrain from naming any here – they know who they are and they are all an inspiration to those of us aspiring to also push the tomato-size envelope. So what do many of these elite growers have in common?
• Dedication, hard work, perserverance, experience (many years in some cases) and knowledge
• Excellent soil resulting from their years of hard (and smart) work
• Proper growing techniques
and, I will suggest,
• Excellent growing conditions
This last point brings us back to air temperature. I put in a concerted effort in 2012 to grow a giant tomato and did finally manage to break 3 lbs., even in the middle of a record hot summer. But 3 lbs. is very far from the biggest documented tomato grown this year:
Big Zac (5.50 Johnston/Butler 2012)(5.58 Timm 2008)
Art and John have been teaming up for years and have produced many impressive tomatoes, pumpkins and other vegetables. They live in southern Ontario.
So I got this wild idea: let’s compare the summer 2012 air temperatures in their neighborhood to those in the Salt Lake Valley. I’ve collected data from the National Weather Service for Salt Lake City, Utah (near where I live) and Buffalo, New York (about 115 miles due east of where Art and John live – presumably the weather should be very similar). For the period of May 01 to October 31, 2012, here are a few graphs I prepared:
Temperature comparison, Buffalo vs. Salt Lake City
Note – this is a PowerPoint presentation with 4 graphs and takes a minute to download; please click on the “Slide Show” icon near the top left for the best view.
I’ll repeat the last graph here for discussion, though the quality is not nearly as good:
Now I understand why growers in more moderate climates are getting 70+ days to grow their big tomatoes!! Basically, anytime between May 15th and October 5th, tomatoes should be able to grow at a decent pace without being forced to ripen quickly because of intense heat. While in my area, from about June 25 to September 1st, a 68-day period, it was very difficult to get fruit to set and those that did set fruit ripened very quickly.
I would imagine this phenomenon is even more pronounced in the deep south. However, in some of those areas, ideal growing conditions might prevail for several weeks in Spring and/or Fall.
This was a record hot summer in the Salt Lake City area, so perhaps that very wide band of red will be less pronounced next year.
Bringing all this back to the tomato I’m still mollycoddling, it set fruit on August 26th, very near the end of this long hot spell. Obviously, it’s way too cold now for it to grow fast like it was doing back several weeks ago. During the 37-day period from September 15th to October 22nd, this tomato gained approximately 3 lbs. If it were still growing at that rate, it would be about 5.8 lbs. by now. Wishful thinking, of course, but this brings me to the main point of this whole discussion –
If tomato growers are serious about trying to break the 26-year-old record, they might want to consider taking measures to control the temperature in the environment immediately surrounding their prize tomato plants:
• When too hot: shade cloth, misters, fans, pipes in the soil with cool water, frequent overhead watering, buckets of ice set around the growing fruit
• When too cold: plastic cover to create a greenhouse effect, electric or gas heaters, pipes in the soil with warm water, heating cables
Many successful giant pumpkin growers employ some of these techniques to control temperature in their pumpkin patches during less-than-ideal weather conditions. I’ll venture to guess the same will be true of the grower of the first
8 POUND TOMATO!!