Unveiling the secrets of rooting powder: what is it, its uses and its benefits.
If you’re the sort of person who takes cuttings (thinking it through: why buy a whole plant when you can start your own from just a little branch?), you know that there’s plants whose cuttings root readily and others that are a bit more difficult to turn into actually living, functional beings. Then there’s the really hard ones, like some fruit trees such as apples, or ornamental plants such as azaleas, figs and dieffenbachias. Then there’s just the impossible: try propagating a banana tree from cuttings and failures will succeed each other, because it’s just biologically impossible to do that.
What lies at the root of these differences, so to say? What makes some plants produce cuttings that root readily, while others are painfully difficult to propagate this way? The answer, from a biological point of view, is simple, but it does require us to get a bit into the science of it all: the plants that can produce roots from cuttings are those that have a vascular cambium. It sounds very medical-y, but really the vascular cambium is just a part of the stem that exists between the inner, woody area, and the outer ‘skin’ of the stem. This part is, to put it simply, a layer of stem cells (yeah, the same kind of cell that forms human babies!) that exists between the inner wood and the bark:
This layer basically distributes new cells towards the bark or the inner core of a stem as it grows, and turns them into bark cells (‘phloem’ cells) or core cells (‘xylem’ cells). But because, while they remain on the vascular cambium, these cells have not a defined ‘role’ already, they can also be turned into roots if the plant receives the necessary stimuli from the environment. So, for example, the wind knocks down a plant and its stems are now half-buried? No problem, the vascular cambium starts turning some of its cells into root cells, and from the stems sprout roots.
Enter these two guys, in 1937:
These two gentlemen are the microbiologists Kenneth Thimann (left) and Frits Went (right). In 1937 they published a book together called Phytohormones (‘plant hormones’). In this book, they expound the findings of their investigations from the prior decade: they had identified and isolated a hormone called ‘auxin’, which they found out could be used to stimulate the vascular cambium. They observed that this hormone, basically, drove the cell production mechanism crazy: roots were sprouting in every direction and at much higher rates in cuttings that, before, produced one or two roots after a while. Soon, these hormones were manufactured and sold to growers in powdered form. The world had gained the first rooting powder for plants, and identified the first plant rooting hormone.
So, what is rooting powder?
In our day, commercial rooting powders (sold often as ‘root powder’) are just synthetic versions of what Went and Thimman found that plants produce naturally: they’re just, in short, powdered plant hormones that stimulate a cutting’s layer of ‘undefined’ cells (once again, the vascular cambrium) to form roots. After their research (because we’ve come a long way, scientifically, from 1937) a ton of other plant hormones have been identified that also stimulate the production of roots. Wikipedia has a detailed list of all the classes of plant hormones that exist: auxins are just the ‘rooting hormone’, so to say, but plants produce hormones for all sorts of other purposes too. There’s a more general plant growth hormone (cytokinin) and a plant growth inhibitor as well (abscisic acid), among many other hormones.
Can rooting powder be replaced?
Because the commercially available plant rooting powder is just a synthetic version of hormones that plants naturally produce, it can easily be substituted. You can make your own plant hormone extract at home, though it will probably not be as effective as commercially available rooting powder, and it will not be in powdered form. It will most likely resemble a liquid, because, after all, natural things do tend to be squishy, slimy, wrinkled or to produce fluids somehow (that’s life for you, folks!). However, even though the convenient powdered form of rooting powder is a side-perk of it being synthetic, natural rooting ‘powder’ has the great advantage of being free. Not precisely a disadvantage, especially if you are a home gardener with a limited budget.
How can I replace rooting powder?
The easiest, most-proven way to replace commercial rooting powder is extracting rooting hormones from willow trees. Willow trees have some of the highest concentrations of auxins in the natural world, especially in the tips of their branches. The basic procedure to extract these hormones is by making cuttings from the newest, greenest branches of a willow tree (any of them will do, but you can aim for the most well-known just to be sure, such as the white willow or the weeping willow); and peeling all of their leaves before crushing the remaining twigs, and then letting these sit in water for two or three days. Filter them out, and use the water as the medium where your desired cuttings (the ones that you actually want to grow) will sprout roots. Then you can move these rooting plants to actual soil, and allow them to really start their growth process. Any rooting plant should not sit in water perpetually, or will inevitably die.
If you’d like to see a more detailed guide for making willow (hormone-infused) water, you can follow this one from the Permaculture Research Institute. This is how their willow water looked like:
Nothing major, as you see, it’s just a bunch of twigs sitting in water.
Some people swear that you can also make homemade versions of hormone rooting powder (again, just not as a powder!) by repeating this process using lentils; leaving them sprout in water and then placing your cuttings in that water after filtering out the lentils. Some also say that aloe vera gel, taken from actual aloe plants, works just as well as a hormone root stimulant. You can try these out too: as always, experimentation and experience are what make gardeners succeed in the end.
Will homemade rooting hormones work just as well?
Rooting hormone powder of any kind will most likely be successful, as long as it is produced in accordance with effective regulations that ensure an actual impact over the plants rooting under its effect. But a powder rooting hormone might not be the best choice for your case: even though they’re far less concentrated than commercial rooting powders, their cheapness (it doesn’t get cheaper than free!) and availability make homemade rooting hormone replacements far more expendable, and far more easily re-applied to ensure that they work in the end. As with anything, it’s better to exercise prudence: if you’ve got just one cutting from this very rare, very difficult to propagate plant, use a rooting powder or a rooting gel. If it’s for everyday use, it might very well worth a try to make your own rooting hormones — and to let us know in the comments how have they worked for you!