In the 1950s, as part of the nuclear energy craze, gardeners exposed seeds or seedlings to gamma radiation in order to induce beneficial mutations. In the UK, seeds were mailed out to enthusiasts to grow.
The protocol was to put the plants in a circular “gamma garden” around a radiation source like cobalt-60 for about twenty hours. Many of the plants died, or got weird growths, as you would expect. Some, however, thrived, and this unusual approach to gardening led to several plant cultivars still in use today, including varieties of peppermint and red grapefruit.