Cuphea suffering from etiolation. Photo: Rachel Bernier
Question: I’m overwintering a cuphea Vermillionaire on my windowsill after a friend tried this last year with success. But I find its growth weak and pale, even if it is placed in my sunniest window. Should I prune it back regularly to strengthen its stems?
Answer: The appearance of your Cuphea Vermillionaire® plant shows it simply lacks light, which explains why it is etiolated (showing weak, pale growth).
Honestly, that’s a pretty normal situation for an overwintering annual. Due to the short days and, in many climates, persistent gray weather, fall and winter sunlight is far less than the plant really needs, even in the brightest window, so it etiolates: stretches as if to try and grab a bit more sunlight. By cutting it back, you’ll at least keep it fairly compact until days lengthen.
And, of course, they will. You should notice a huge change in the plant’s growth in starting in March and early April. Its new stems will be shorter and its foliage denser and greener. In fact, as spring progresses, it will probably start blooming again to a certain degree, although not as heavily it will outdoors (indoor sunlight is never as intense as sunlight outdoors).
When there is no more risk of frost, acclimatize your cuphea to outdoor conditions and give it full outdoor sun. In no time it will again be as gorgeous as it ever was!