Pollination and isolation

Most tomatoes are not capable of cross-pollination as the flowers are perfect and self-pollinating. The female stigma is very short, and grows within a tube formed by the fused anthers.  For these types, different varieties can be grown close together. Below are examples of flowers with protruding and enclosed stigmas:

Tomato with protruding stigma Tomato with enclosed stigma

There are three exceptions: currant tomatoes (Solanum pimpinellifolium), potato leaved varieties, and double blossoms on beefsteak varieties.  These often have a protruding stigma and are able to cross-pollinate, especially if there are other protruding-stigma varieties in the vicinity. To be absolutely certain, check a few newly opened flowers using a hand lens.  The green stigmas will protrude from the anther tube. For safety, you could grow just one protruding-stigma variety a year. Or, you may want to cage plants or bag trusses, the flowers will self-pollinate within these.  


If you find you have a cross-pollinating tomato variety, for safety, you could grow just one protruding-stigma variety a year. Or, you may want to cage plants or bag trusses, the flowers will self-pollinate within these. 

Example of bag trusses Example of a mesh cage for isolation