Why is it that every seed catalogue on my desk falls open to the tomato pages? Perhaps the seed companies have recognized my tomato obsession — bred in the bone, so to speak, from a tomato-growing family. My grandfather grew ‘Rutgers’ (developed in 1934 by Rutgers, New Jersey, Agriculture Experiment Station breeder Lyman Schermerhorn) in his garden for 50 years.
My current interest is fixed on sweet cherry tomatoes. The supermarkets stock brands of cherries in different sizes and colours (but without identifying cultivar names), and the seed catalogues are loaded with varieties for home gardens. Many are named for their sweet potential — ’Sweet Baby Girl’ (parkseed.com), ‘Sugary’ and ‘Sweet Chelsea’ (veseys.com), ‘Sakura Honey’ (johnnyseeds.com), ‘Red Candy’ and ‘Sweet Mojo’ (stokeseeds.com). Their sweetness has universal appeal, but how sweet are they? I’m a gardener, not a chemist. I looked around on the Internet and found some interesting information about sweet flavour in plant fruits.
Fruit sugars are expressed in Brix degrees, a scale for measuring the density of sugar in a water-based solution. The tool for this measurement is a Brix refractometer, or sugar tester—a six-inch (15-cm) pocket-size optical device. It works by squeezing a drop of juice onto a small glass window and looking through the device for a measurement. The Brix scale is essential in wine making, as it reveals the sugar content of grapes on the vine and when they are optimally suited for harvest. The scale runs from 0 to 40 per cent, and can be used to measure sugar in any solution (including cola drinks if you want to blow it off the chart!), or drops of juice squeezed from home-grown fruit or vegetables like berries, peaches and tomatoes. Some gardeners have written about their tomato-growing experiments, and while their information is not meant to be scientifically reliable, it’s certainly insightful about sweet flavour in cherry tomatoes.
The sweet flavour of tomatoes is influenced by the plant’s capability to manufacture both sugar and acid, by seasonal growing conditions (tomatoes produce less sugar in a cloudy summer) and by the gardener’s cultural practices (if you don’t water tomatoes through a drought, their sugar plummets). The acid is measured with the pH scale that is also used for indicating soil acidity and alkalinity. As an example, natural pineapple juice has a sugar rating of about 16.2 degrees Brix, and an acid rating of about pH 3.8. The relationship of the two measurements works like this: sugar flavour increases as the Brix measurement rises; the pH scale works backward to lower numbers, and acid flavour increases as the pH measurement lowers. The high sugar content in pineapple juice overwhelms the extreme acid in the fruit, and produces a sweet flavour.
Mystery-variety supermarket cherry tomatoes are generally around 4.8 Brix degrees, with acidity around pH 4.1, and you probably have an idea of what they taste like. Compare that with one gardener’s ‘Sweet Million’ cherry tomatoes, with a sugar content of 7.1 Brix and pH 4.1. Now that’s a sweet tomato!Sometimes seed catalogues will offer the Brix rating for tomatoes with high sugar capability. Stokes Seeds lists ‘Sweet Orange’ as having 9 to 10 degrees Brix, and ‘Cupid’ with 8.2 degrees Brix. If you want cherry tomatoes (or larger sizes of tomatoes) with a sweet taste, start plants from seed and select cultivars that are capable of producing high amounts of sugar. (Fortunately, ‘Sweet Million’ is sometimes found as started seedlings in garden centres.)
I’ve decided to have my own Brix refractometer ($59.99 at leevalleytools.ca). It’s a good tool for someone who loves growing tomatoes; and it’s also an idea for horticultural clubs to own one for their members’ use. Tomato-tasting competitions are great summer events for gardeners and I always enjoyed this at my Master Gardener group. If a Brix refractometer is available to give precise sugar ratings, this would really add a competitive edge. It’s all about growing the sweetest cherry tomatoes.
More about tomatoes
Useful plants: goat’s beard
To my mind, a useful plant is one that solves a problem — it will grow in challenging circumstances, requires little maintenance beyond irrigation (everything needs water) and is non-invasive (unless I want it to be). Goat’s beard (Aruncus dioicus, 5 feet x 40 inches/1.5 m x 1 m, Zone 4) is a large-scale perennial (looking something like a large astilbe) and a good gap filler in borders or massed under trees. The handsome foliage is fern-like in a husky way, and the creamy flower plumes arise in late spring on tall scapes, lasting for three to four weeks. When the flowers are finished, the seedheads can be cut back, and the foliage clump is an asset all summer. I grow it in dry shade, but this year will be putting some into areas of half-day sun, and I expect more and larger flower plumes in the brighter location. Look for the species plant, which is larger and showier than any of the named cultivars (such as ‘Kneiffii’, ‘Zweiweltenkind’ and ‘Southern White’).