by Patty Gray, Pacific Garden Program Director
That’s how I always thought of Sacramento and the Central Valley when I was spending part of my childhood here. In my memory, tomatoes were everywhere, always ripe, always perfect. I later had good success growing my own tomatoes in Southern Illinois, but then my travels took me to much cooler climes, first to Alaska, and then to Ireland. After spending the last eight years struggling to grow the juicy orbs in cold, damp, mostly-cloudy Dublin, I thought growing tomatoes in Stockton would be fool-proof.
So does that make me a fool? Because here in the Robb Garden at University of the Pacific, we had practically no tomatoes this summer. Out of twenty plants, only about half produced any fruit at all, and most of those were cherry varieties. The big, plump, sun-ripened beauties I had imagined – and hankered for – never materialized.
Legend has it that Dr. Mark Brunell, when he served as faculty garden director in the Robb Garden 2012-2014, had 100 varieties of tomatoes planted, with the vines groaning under the weight of abundant fruit. When I arrived at Pacific a year ago in July, the Robb Garden sported a bumper crop of ripe tomatoes. We harvested basketsful every week, well into Fall.
This year we are already preparing to yank the plants out in mid-September, in an admission of defeat.
Just about the time I was ready to conclude I’m not the gardener I thought I was, I started getting reports from other gardeners in Stockton that they’ve been experiencing similar tomato misery. Commiseration is a wonderful resource for gardeners. It’s a chance to engage in mutual reassurance that it isn’t us, it’s Mother Nature conspiring against us. Even local Stockton gardening heroes were functionally tomatoless this summer.
When the average temperature of your hottest month is 60 degrees, as it is in Dublin in July, all you can think of as a remedy for your ailing tomato plants is more heat. It just never would have occurred to me that you could have too much heat. But of course you can. Stockton experienced a perfect storm of adverse tomato weather this summer.
Tomatoes grow best when daytime temperatures are anywhere from 65 degrees F to 85 degrees, and when nighttime temperatures do not fall below 55 degrees. If temperatures get above 95 degrees, fruit will not set on tomato plants. What’s worse, if nighttime temperatures fail to drop below 85 degrees, fruit that has set won’t ripen.
So Stockton’s weather this summer was basically a tomato disaster. During the critical window for tomato plants to flower and set fruit, temperatures were way too hot – a look at the Weather Underground historical pages for Stockton shows that we had 13 days above 95 degrees in June, 28 such days in July, and 19 such days in August. And many of those days were well over 100 degrees. The records show that low daily temperatures were plenty below 85 degrees F, but I wonder if in the Robb Garden – situated as it is amidst heat-radiating pavements and concrete buildings – does not experience warmer nighttime temperatures than the local averages.
Next year we will be ready. There are ways to place tomatoes so as to shade them during the hottest part of the day, and we can do a much better job of mulching and making daily checks of soil moisture. We cannot control nature, and our beloved tomato varieties cannot adapt to these heat extremes, but we can mitigate the effects to some extent.
We’d better start honing our mitigation skills if we want to keep enjoying ripe local tomatoes, because we might have those summer heat extremes with us for some time to come. Believe it or not.