MANHATTAN, Kan. – Heirloom vegetable varieties are a "tremendous interest" now in gardening circles. But heirloom tomatoes, in particular, bring two big problems, warns a Kansas State University horticulturist.

One of those problems literally is big in size.

The other, however, is big in scope. It relates to a disease fungus that can survive in soil for eight to 10 years, added Chuck Marr, K-State Research and Extension’s vegetable crop specialist.

"Nearly all heirloom tomatoes are what’s called indeterminate. That means they develop huge vines – to produce no more tomatoes than you can harvest from today’s smaller, improved varieties. Naturally, big vines not only take more space, but also need more water and use more soil nutrients. They’re simply not very efficient," he said.

Marr is more concerned, however, about the fact heirloom tomato plants don’t have the disease resistance bred into newer hybrid varieties. This opens the door for a vine-killing disease that used to be the bane of tomato production: Fusarium wilt.

"Even today’s resistant varieties aren’t totally immune to Fusarium wilt, particularly if your soil gets severely infested. That’s why we still recommend that you never grow tomatoes in the same garden site from year to year," the horticulturist said. "We’ve managed to reduce incidence of the disease in Kansas to the point that it’s no longer a concern. But the fungus is out there in places. And an heirloom plant is an open invitation for it to get going again."