Growing Heuchera villosa Hybrids in a Greenhouse
Here are a few hints for growing success with Heuchera villosa hybrids
1) Keep them Cool and Shaded
Thanks to the villosa parentage which is native to the southeastern U.S, one of the greatest attributes of the villosa hybrids is their versatility in the landscape: they can thrive in both sun to part shade, both slightly wet to slightly dry soil, and low to high humidity. Although, take note that when plants are young and growing in a pot, they do prefer some shade to moderate the temperature and reduce intense afternoon sun. This keeps the plants from stressing too much which tends to bring about a significant loss of plant vigor, abnormal growth of the foliage or increase susceptibility to crown and root pathogens.
2) Grow them Lean
One of the best lessons I've ever learned about growing any Heuchera in a greenhouse is to grow them lean. Try not to love the villosa hybrids too much (I know that will be difficult to do)! These heucheras will thrive in a variety of well-drained soiless medias, with minimal fertilizer. While they can handle short periods of higher fertility or pH making them more forgiving to grow, generally about 50 ppm nitrogen continuous feed will sustain them very well. We have found an acceptable pH and EC range for the villosa hybrids to be between, 5.8 to 6.2 and 2 to 3.5, respectively (using pour-thru method). Water plants thoroughly and then allow them to dry down before watering again. This is a natural way to regulate their growth and, in conjunction with fertility management, reduces disease susceptibility to pathogens such as Fusarium, Pythium or Thielaviopsis, among others.
3) Pest Management
For the grower moving towards more sustainability, searching for trouble-free plants for mixed containers or those that are a little bit less work, these Heucheras lends themselves wonderfully to those options and more. Scout for aphids and botrytis but mostly keep an eye out for any sign of crown or root rot. Villosa hybrids are quite resilient, even under short periods of less than ideal conditions in the greenhouse. They are also naturally less prone to what I call "spontaneous combustion disease". This is my admittedly un-scientific term for those frustrating times when you walk in your greenhouse one day to admire seemingly happy and healthy Heuchera only to walk in a few days later and exclaim "What happened?!", as you find some plants have suddenly taken a turn for the worse which could be caused by any number of poor culture issues and pathogens.