The caller sounded puzzled. He’s been rooting cuttings for years, heard me talk about Hormex on the radio, and visited the website. In all those years, he said he’d never seen more than a couple of different strength rooting hormone products. Does it really make a difference which strength you use? Why not just get the strongest one and use it for everything? His questions gave focus to this week’s blog.
Hormex Rooting Powder comes in 4 strengths with specific applications to suit several plants and plant groups. They are numbered and higher numbers indicate greater strength concentrations of IBA, the active ingredient. IBA, indole-3-butyric acid, is a naturally-occurring plant hormone vital to the cell elongation process involved in rooting. Just as different plant groups thrive in a range of sun, soil, and maintenance conditions, they develop roots best at particular levels of the rooting hormone IBA. To stretch the analogy a bit further, a plant that needs only weekly watering can be drowned by greater amounts that fatally reduce the available oxygen in the root zone. In the same way, a plant that can root in Hormex #3 will find that growth stunted in Hormex #30 and vice versa. Use the right strength for the right cloning power to produce roots in the fastest time.
I’ve been thinking about this issue a lot since that call last weekend and the short answer is: Yes, it makes a difference which Hormex product you use and No, it won’t work to use the strongest for everything. Now that we’ve cleared that up, here are some notes about the plant groups and their preferred Hormex Rooting Powder.
The label of HRP #1 explains that it is for use on easy to propagate plants including common shrubs and greenhouse plants. Herbaceous or green plants like members of the square-stemmed Mint family (coleus, verbena, etc.), some plants which are woody but root easily with their leaves on such as jasmine and rose, and a roster of in-between plants respond well to HRP#1. This strength works for stems that are green at times and woody at times such as bougainvillea, raspberry, azalea, and willow. It is the go-to strength to try first and also works on plants as diverse as begonia and African violet.
As their strengths increase, Hormex powders stimulate rooting in woodier plants and harder-to-root evergreens. For example, HRP #3 works for popular evergreens like junipers, fruits such as blueberry, as well as pyracantha and Daphne. All need coaxing to form roots but will be discouraged by stronger Hormex formulas.
The truly difficult to root evergreens and dormant hardwood cuttings of deciduous azaleas, grapevines, lilac and maples including Japanese maples respond well to the stronger HRP #8. These plant groups need higher levels of IBA to speed rooting and improve the quality of roots formed. I know this is just one person’s experience, but I had tried and failed to root native azaleas several times before I used #8. The cuttings I took in February are looking good!
By now you have probably realized that some members of a particular family are more difficult to clone than others. Junipers, for example, can be easy or difficult depending on the species or cultivar. Chinese junipers take #3, but the truly tough customers are the Hollywood junipers which need #16. Common names can be misleading, too, like this example: classic arborvitae will root with #3, but the pyramid arborvitae (actually Thuja) responds to #16. Their rooting will be slowed or not helped at all by lesser formulas, just as the plants that can root with less concentration will be overwhelmed by greater strengths.
One more note: I was first introduced to Hormex Rooting Powder in horticulture school, but found a stalwart fan when I began working in California. A grower friend of mine gave me a variety of cuttings when I toured his greenhouses. As I was leaving he summoned me to the head house, the greenhouse equivalent of a potting shed, where a jar of Hormex sat on the bench. He poured about a tablespoonful into a clean envelope and handed it to me with instructions to use it on the woody cuttings. Since I knew him to be a man of few words, it was surprising when he launched into a 5 minute tribute to the great cloning successes he’d had since starting to use Hormex. But once I started using it, I understood completely.