Knowing your tomatoes

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Zahrah Nasir

Tomatoes are one of the easiest and potentially most productive veggies to grow, although — botanically speaking — they are classified as fruit. The basis of so many of our traditional recipes these days, tomatoes are indigenous to South America and were introduced to our part of the world by European colonists, probably sometime in the 1700s, which makes one wonder what we added to our food before their arrival.

Members of the solanacea family of plants, as are aubergines, capsicums and chillies, are basically divided into two strains: 1. Lycopersicum lycopersicum, the regular tomato; and 2. Lycopersicum pimpinellifolium which are the sweetly delicious cherry tomatoes.

These two strains are further divided into determinate and indeterminate types. The first of these, determinate, produce lots of fruits over a very short period of time. The indeterminate types produce and ripen their crops of fruit over what can be a surprisingly long period, providing that optimum growing conditions are maintained.

Naturally and purposefully assisted, tomatoes have diversified down through the centuries. In the process, these have adapted to being cultivated in a wide range of climates and soil conditions too.

Successfully cultivated as far north as bitterly cold Greenland, their leaf forms have also undergone structural changes to cope with the vagaries of different climates and the variable lengths of daylight hours they can now endure.

The most obvious of these leaf form changes are markedly visible in cold-tolerant varieties, which are larger than ‘normal’ leaves. These, known as potato-leafed tomatoes, are able to take full advantage of the limited amount of sunlight the cold, short-daylight summers the far-northern climates have to offer. Those who have tried growing potato-leafed varieties over the summer months here in Pakistan may very well have had severe problems with diseases such as tomato blight and mildew or have been generally disappointed by the poor crops achieved.

The reason for this is that, in evolving to produce and survive in cold climates, their ability to tolerate heat has been compromised. Potato-leafed varieties can, however, be successfully grown throughout the plains and coastal regions of our climatically diverse country over the relatively cool months of winter.

Determinate tomato varieties may or may not require support frameworks, but indeterminate ones usually do, unless, of course, they are of a bush habit. There is much debate in tomato growing circles about the pros and cons of side-shooting tomato plants of determinate and indeterminate tomato vines. Side-shooting is the practice of removing all new shoots sprouting from leaf axils on the main stems, to force the vine to focus on growing tall and strong, and to potentially increase flowering and fruiting at the same time.

Vines grown this way need very tall, strong support frameworks and side-shooting needs to be done every 2-3 days throughout the growing season. It is true to say that side-shooted vines are less susceptible to blight and mildew as air circulation is maximized around the plants but — as the on-going arguments go — heavy crops can be achieved by simply allowing plants to bush and out and grow as nature intends them to do.

Having written about the soil conditions preferred by tomatoes in previous columns, I won’t waste space by repeating it here but, instead, will share a little advice on saving their seeds. Tomatoes are self-pollinating and saving their seeds is fairly simple.

‘Heritage’ and cherry tomato varieties are more liable to be cross-pollinated, by insects/ wind, than more recently developed varieties, and should be grown in blocks of just one variety if you intend saving seed. Harvesting seeds from tomatoes growing in the center of the block is the best way of ensuring purity of type is maintained.

More modern tomato varieties are less liable to cross-pollinate; this is because of the shape of internal flower parts, which have developed to result in almost instant self-pollination.

In either case, the fruits on the first 3 trusses (bunches) to form are the best ones for saving seed from. Leave the selected fruits on the vine until they are slightly over-ripe. Cut the fruit in half and squeeze out the seeds and surrounding jelly-like substance into a small jar/ bowl and leave, uncovered and undisturbed, in a warm place, for 2 days.

During this time, a special kind of fermentation will take place: this antibiotic fermentation inoculates the seeds against a variety of tomato diseases. Do not allow the seeds to ferment for more than 2 days or they will begin to germinate and die off.

Scoop the fermentation foam off and put the seeds and jelly into a small sieve, then rinse with water until the seeds are clean. Spread the clean seeds out on a sheet of greaseproof paper. Allow them to dry out of direct sunlight, swishing them around every once in a while, to prevent them sticking to each other.

After a couple of days, put it into a paper bag/ paper envelope and hang in an airy place to fully dry for two weeks. Finally, label, date and store in a cool, dry, dark, place until next sowing time comes around.