Hartley Magazine

All the latest news, hints, tips and advice from our experts

Tomatoes 101 – Year Round Love in the Greenhouse

In northern parts of America greenhouse owners are just now starting tomato plants from seed ready for the new season. Under lights on the heat mat I have some fifteen varieties growing. These will be transplanted into larger pots until they are ready for my garden and the gardens of friends. But often tomato varieties come with a confusing array of letters after their name. To help get you up to speed on the terminology, here’s a primer on the most common terms.

Let’s start with heirloom and hybrid. Heirloom tomatoes are varieties reproduced through natural pollination that have stayed true to their type for at least 50 years. Gardeners love heirlooms for their flavor and often unique shapes and colors. Hybrid tomatoes, in contrast, are varieties obtained by intentionally crossing parent plants possessing different traits to combine those traits in offspring.

For instance, a plant resistant to verticillium wilt might be crossed with one that has bountiful crops to yield a disease-hardy, highly productive hybrid. Be aware that the seeds of most hybrids don’t reliably reproduce plants with the same characteristics as heirloom tomatoes do. A hybrid’s genetic combination of traits breaks down over time.

toma - 1st April

What about early, mid-season, and late-season? What exactly do these terms mean? Under optimum growing conditions, early tomatoes will mature in 50 to 60 days (I start early tomatoes in January to get fresh fruit in the middle of May in my greenhouse), mid-season ones in 60 to 80 days, and late-season ones in more than 80.

Don’t take these time ranges too literally, however. The actual number of days to maturity will vary depending upon such factors as planting time, soil temperature, moisture level, and so on. Note, too, that the time to maturity is usually directly related to the size of the fruit, with early tomatoes generally being smaller and late-season ones the largest.

The preferred use for different tomatoes can often be deduced from their names. For example, paste tomatoes tend to be meaty and are excellent for making thick sauces; cherry tomatoes are the size of large cherries and can be popped in your mouth like these tree-grown fruits; and grape tomatoes are even smaller, making them ideal for salads. Currant tomatoes may be even smaller for decorating salads and other dishes.

The terms determinate and indeterminate are also ones you should know. Determinate tomatoes set all their fruit at once and then stop growing, making them ideal if you want many tomatoes for sauces or soups. Indeterminate tomatoes, in contrast, keep producing as long as nighttime temperatures stay above 55oF. This makes their fruit perfect for salads all summer long.

And finally, you should know that the letters on tomato seed packets indicate resistance to particular diseases. These letters are frequently combined into strings, such as VFNLB. Here are their individual meanings:

V: Resistant to verticillium wilt

F: Resistant to fusarium wilt

FF: Resistant to both types of fusarium wilt

N: Resistant to nematodes

TMV: Resistant to tobacco mosaic virus (Smokers tend to pick up TMV from their cigarettes.)

LB:  Resistant to late blight

SVW:  Resistant to spotted wilt virus