UNITED STATES—‘Jewel Mix’ nasturtium starts out so colorful with various shades of yellow, orange and red, including rich reddish brown and almost white pale yellow. They happily sow their own seed to replace older plants. However, as new plants replace old, the variety of color diminishes. Brown and pale yellow are the first to go. Red then becomes scarce. Eventually, only bright orange and bright yellow are the only two colors remaining, which is certainly colorful enough for those of us who really dig nasturtiums, but considerably different from the original blend.Reversion is the natural tendency for plants to revert to a more genetically stable state. For ‘Jewel Mix’ and certain other varieties of nasturtium, plants that bloom with the familiar orange and yellow flowers are more genetically stable than plants that bloom with the various other shades. Seedlings tend to be more stable than their parents, so are naturally more likely to bloom with one of these two ‘stable’ colors. After a few generations, the less stable types get replaced with the more stable types.
Blue fescue is not likely to be completely replaced by younger generations, but sometimes produces seedlings that are conspicuous for their unique foliar color. It is hard to ignore a single clump of grayish green foliage in an otherwise homogenous bed of striking blue foliage. Plants with greener foliage often exhibit distinct texture as well.
Even without sowing seeds, some genetically unstable plants sometimes produce mutant growth known as ‘sports’, that are commonly more genetically stable than the plants that produce them. Variegated plants like Algerian ivy, Pittosporum tobira and Houttuynia cordata, are notorious for producing unvariegated growth. Because unvariegated growth has more chlorophyll, it grows faster and often overwhelms variegated growth. In fact, mature variegated Algerian ivy that has not reverted to green (unvariegated) is rare. Lily-of-the-Nile sometimes reverts back and forth between seemingly equally stable (or unstable) blue and white blooming growth.
To maintain genetically unstable plants in their intended state, sports must be pruned out as they develop. For Algerian ivy, this can be daunting! Seed grown annuals must be replaced with new seeds regularly, instead of allowed to naturalize. Of course, there is nothing wrong with unvariegated Algerian ivy, and exclusively yellow and orange nasturtiums!
highlight: blue fescue
The dense tufts of finely textured but relatively stiff leaves of blue fescue, Festuca glauca, might look rather silly those who do not appreciate the bluish gray color and distinctively compact form. They do make a neat border for mixed perennials though. They also work well mixed with small perennials or annuals. Mature plants are less than ten inches high and broad, although ‘Siskiyou Blue’ can get twice as large. The thin flower spikes that bloom in summer are not much to write about. Seedlings that occasionally grow around undisturbed plants may exhibit variation of foliar color.
Even with good sun exposure and good drainage, old blue fescue plants eventually go bald in the centers. When that happens, viable parts can be divided into small new plants during the following autumn.
By Tony Tomeo