The Dry Garden: Heirloom tomatoes by trial and error

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A tomato left to rot in the garden last summer resulted this spring in my eating ripe homegrown heirloom tomatoes by Memorial Day instead of the normal harvest time around the Fourth of July. A fruit dropped in mulch sprouted in October rain, did nicely through winter storms and then, with some watering since May, the vines have been yielding what I’ve decided must be Cherokee Purple tomatoes for going on a month. In terms of flavor, they’re not Black Krims. No other tomato is. The word online is that Cherokee Purples rival Brandywines. That is true.

In other words, they’re good enough that, with heirloom tomatoes of this quality costing $3 a pound in farmers markets, I thought I might be on to manna for readers. So I rang UC Davis’ C.M. Rick Tomato Genetics Resource Center to ask why every gardener in Southern California doesn’t plant tomatoes with their poppies -- in the fall. Director Roger Chetelat’s response boiled down to two words: disease and pestilence.

Evidently, allowing plants, including volunteers, to over-winter offers viruses and insect predators safe harbor and is not to be encouraged. Instead of getting a head start, you could be ensuring the loss of your crop.

I took his point, but I was more chastened by the realization that I had been eating well out of dumb luck. I had no idea what my plucky little vines were going to yield, and I watered them on a gamble. Nursing volunteers from fallen fruit or the compost pile in years past has produced some real duds, mainly flavorless approximations of the plum tomatoes used by the canning industry.

It’s the genetics, Chetelat explained. Keeping reading for more ...

Heirloom tomatoes, such as my Cherokee Purple, have been bred for so long for certain characteristics that they come true from seed, whereas the genes of seedlings grown from modern hybrids ‘segregate all over the place.’ Hence my disappointing years. Volunteer plants from cherry tomatoes also tend to stay relatively true, he said.

Beyond protecting plant health and ensuring that the time spent watering and staking the plants is worth it, there is another reason to prefer spring sowing: weather.

Winter was celebrated for its slightly above ‘normal’ rainfall, but there was nothing normal about it. It was a particularly temperate winter with a genteel succession of rains that started early and lasted late. Wet seasons as even-tempered are rare.

Moreover, last month forecasters began a La Niña watch, a move that augurs the kind of dry year that could tax native poppies, never mind tropical tomatoes. The worst circumstances for a tropic vine over-wintering in our Mediterranean climate would be dry conditions with sharp cold snaps, as happened in 2006-07.

The upshot? If I want Cherokee Purples next year, I’d be well advised to save some of the seeds instead of banking on fallen fruit producing bounty. ‘Squish them out into a jar,’ Chetelat said. ‘Let them ferment on counter. The fungi will work on fruit pulp. Rinse in a strainer and pop the seeds onto paper to dry them.’ (UC Cooperative Extension offers more detailed instructions on how to save tomato seeds.) Store seeds in a cool dry place, then start them inside next April. Ninety days later, you should have fruit, probably closer to the Fourth of July than Memorial Day, unless something wonderful happens.

-- Emily Green

Green’s column on sustainable gardening appears here every Friday morning.