There are some very interesting facts about tomatoes. No one can say for certain, but the ancestor of all modern tomato varieties appears to have been a scrambling vine that was native to the highlands of Peru. Archaeological evidence suggests that these wild plants were harvested for their small green berries. The first domestication of the tomato was by the Aztec people of central Mexico who grew it for its small, cherry-sized yellow fruits. They gave it the name Xitomatl (swelling fruit), from which we get the modern English word, “tomato.”
Both of the explorers Cortes and Columbus are credited with bringing the first tomato plants back to Spain some time near the dawn of the 16th century. By mid-century the fruit had been described by Italian botanists, and given the name pomo d’oro — the “golden apple.” Whatever the exact history of the plant is, one thing is for certain: The Spanish adopted the fruit as a foodstuff and spread it to their colonies around the globe.
It took a century of tomato growing in Mediterranean Europe before the plant first appeared in British gardens in the late 1590’s. But even then British herbalists thought it unfit for eating, and was not used as a culinary plant until the mid-18th century. By the mid-19th century, tomatoes had spread around the world.
Because plant breeding is relatively easy with tomatoes, there are as many varieties as there are cultures that grew them. Many of these now travel around the world as heirloom varieties, handed down from one generation to the next, imported to the New World from the Old, or from traditional agricultural communities (like the Amish and Mennonites) to contemporary nursery shelves (and seed racks!). A tomato is considered to be an heirloom if it has been grown and re-grown via seed saving for around 50 years. Most heirloom varieties were popular before the spread of industrialized agriculture that followed WWII.
All this plant breeding has led to a very diverse range of colours, sizes, shapes, flavours, and other characteristics. They can be categorized in a number of different ways. We’ll start with size and shape.
- Beefsteak tomatoes are the largest in size, usually quite wide and squat in shape with substantial weight. Many have thin skins, giving them a short shelf life.
- Oxheart tomatoes are also heavy and large, but are heart-shaped, a bit like strawberries.
- There is an intermediate, medium sized, round tomato type that doesn’t really have a category name.
- Plum tomatoes and Roma types are oblong to round, with meaty flesh that is ideal for cooking.
- Campari tomatoes are smaller than average, but still larger than cherry varieties. They are known for sweetness, juiciness, and low acidity.
- Cherry tomatoes (round) and grape tomatoes (oblong) are both quite small, and often have higher sugar content than the larger types.
Another way to divide up tomatoes is by their growth type. All tomatoes were once vines, with indeterminate growth. But some varieties have been bred to be stockier, and we call these bush types determinate. Determinate plants tend to put on foliar growth, bloom, and then set their fruits over a fairly short period. Indeterminate types, however, continue to bloom and grow simultaneously, producing huge plants with lots of fruit until the end of the season. In greenhouse settings, indeterminate plants can remain productive for as long as three years, whereas all determinate types are annual, and will die back after the first period of fruit set. Semi-determinate types also exist, which will produce a second major fruit set before dying back.
Tomatoes can also be categorized by heirloom vs. modern, and by open pollinated vs. hybrid. As we noted above, heirloom simply refers to the length of time a particular variety has been in cultivation. Varieties developed in more recent times may be just as good — or better, in some cases — than their forebears due to breeding for performance in regional climates. They may be bred to mature very early in the season, or to have better disease resistance.
Similarly, hybrid tomatoes, in some cases, will be more productive, sometimes with better disease resistance or a longer shelf life. The only drawback with hybrid varieties is that the seeds they produce tend to not grow true to the parent plant. If you were planning on saving seeds from year to year, you’d want to stick to the open pollinated varieties. If saving seeds is not something you plant to do, the hybrids are worth considering.
Growing Tomatoes in South Coastal BC (and elsewhere!)
For tomato growers in Coastal BC and the Pacific Northwest, the primary consideration may be planning around Late Blight. The blight is a fungal disease that spreads by spores traveling through the air. In Coastal BC, “we have blight.” That is, the spores are here, and it’s something we just need to work around.
If a spore of Late Blight happens to land on a wet tomato leaf, or a tomato leaf in sufficiently high humidity, it will send filaments into the plant’s tissues, and begin to infect the whole plant. Blight almost always turns up at the worst time, too. Symptoms appear suddenly on plants that look otherwise healthy, just as the fruits are about to ripen. Large areas of the plants show dramatic brown and black infected areas, and the fruits soften, turn black, and then the whole plant collapses. Suffice to say, it is well-worth avoiding.
There are a few strategies one can employ in order to avoid Late Blight:
- Keep the tomato’s foliage as dry as possible at all times. Usually this is accomplished by growing the plants beneath some sort of shelter that will keep both rain and dew from wetting the leaves. You might build a cloche, a shelter off the side of your house, or put up any manor of simple greenhouse.Whatever design you use, it should be easily ventilated — as summer temperatures increase, condensation appears on the interior of the structure. That moisture also creates a good environment for blight.
- Aim for the earliest possible crop. Fast maturing varieties are available that may be able to set fruit and be finished before blight becomes a serious problem. These early maturing varieties should also be protected from rain and damp.
- Copper sulfate powder (Bordo) can be applied to the foliage of tomato plants in hopes of preventing the blight from actually infecting the plants. The down side of this approach is that the powder is water soluble, and needs to be applied again every time it rains.
Tomatoes need a long time to mature. The seeds are slow to germinate, and the plants require a period of vegetative growth before they can begin to flower. After fertilization of the flowers, the growth and ripening of the fruits takes time as well. This is why we start tomatoes indoors in late winter or early spring. The seedlings are grown out slowly before being transplanted outdoors as spring temperatures warm up.
As spring progresses, keep your eye on the evening weather reports, and watch for the nighttime low temperature to reach 10°C (50°F). At that point, it’s pretty safe to transplant tomatoes (plus peppers & eggplants) outdoors, or to ventilate your greenhouse at night. Transplanting out when temperatures are cooler than this is technically possible, but may stress plants unnecessarily.
We like to apply a balanced organic fertilizer at transplant time. This will provide adequate nutrition for vegetative growth and flower formation. Supplemental feeding is probably not necessary until the flowers have formed. The micronutrient calcium is necessary for good flower formation and fruit set in tomatoes. Calcium deficiency sometimes reveals itself as Blossom End Rot — the blossom end of the fruit turns soft and pulpy, and the fruit loses its overall appeal. This calcium can be added into the soil by a light application of dolomite lime, or through a calcium-specific fertilizer.
Tomato plants need fairly steady moisture levels, too. If the soil is allowed to dry out in hot weather, and is then flooded with water, the fruits may split. Even moisture throughout the season will result in more consistent fruit. If you’re growing in containers you may need to water once, or even twice, daily.
Tomato flowers are self-fertile. That means that they do not require insects or other means to move pollen from one flower to another to be fertilized. Rather, pollen grains within each flower are shaken loose, and fertilization occurs within the flower. The fertilized ovary of each flower swells into a fruit (which is technically a berry), and as the fruit matures, it changes colour and its sugar content increases.
When tomatoes are ripe, of course, their sugar content is at its peak. This is why homegrown tomatoes (and other fruits & vegetables) have so much more flavour than the ones you can buy in a store. Fully ripe tomatoes are difficult to transport because they are softer, so they rarely appear in shops.
Once you understand the few challenges associated with growing tomatoes, it’s just a matter of patience and experimentation. There are over 7,500 varieties of tomatoes in the world. While you may happen upon a tried and true variety, it’s fun to try new ones each season. Grow for size, for flavour, for canning or cooking, and grow for sharing.