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Tomato Plant Types

Dwarfs and Micros

Part 2 of 2

Indeterminates, determinates, and semi-determinates are the three main plant types most people know of; they can generally be found in most greenhouses, but the market is broadening thanks to the efforts of many breeders. Lesser-known plant types are beginning to pop up and grab the attention of many growers for some very good reasons. Dwarfs and micros can both be grown in pots on patios and balconies, allowing senior citizens and apartment dwellers to take part in gardening once again. Let’s look at the differences.

Dwarfs are the latest craze but are highly misunderstood; most people confuse them with determinates because of their short, bushy stature. These newer types of dwarfs are still shorter, like a determinate (two to five feet tall), but they continue to grow and produce as an indeterminate would until frost kills them.

Dwarfs are an expression of the dwarf (d) gene. They have a shortened, thickened main stem; have shorter internodes (somewhere between one to two inches shorter); and quite often have rugose leaves that make them appear thicker and crunchier, much like that of a winter spinach leaf. They come in a wide variety, which explains why there are at least nine different alleles of the dwarf gene! My favorite is the broccoli (b) allele—I’ve always said that certain dwarfs look like husky little broccoli plants to me. Please see my attached citation from the Tomato Genetics Resource Center (TGRC) for more information about the different types of dwarf expressions.

The final plant type we mentioned above were the micros. This is where genetics are the most intricate; with micros, there is much to be discovered and recorded. In most micros, the plant type depends on a combination of the dwarf gene (d), and either the determinate (sp) or the semi-determinate (sdt) allele. Many micros even contain the recessive sun dwarf (sd) gene, which relates to lighting. The sun dwarf gene allows the plant to stay short and more compact in high-light environments, but if placed in poor or low-light areas, these plants will reach greatly for the light, sometimes growing three times their projected height. Most micros have the typical characteristics of a dwarf, except the internode spacing is much shorter, with some less than a centimeter between leaflets. Micros are ideal for both indoor and outdoor conditions, as long as there is ample lighting. Some can even grow in small half-gallon pots. For this reason, many tomato enthusiasts choose to grow them indoors during the winter months. Some examples of micro tomatoes are Tiny Tim, Orange Pinocchio, Aztek, and Venus.

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