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Who doesn’t enjoy the contrast of the translucent green foliage inside a clear glass container? It’s delicate and it’s also amazing how long cuttings can carry on, even without growing roots. And in the dark. In fact, although I have a hundreds of houseplants to choose from, I have more leaf cuttings in water at home than I have actual potted plants. If nothing else, you certainly can’t deny the economy of free foliage.
But what about water cuttings, not for beauty sake, but for actual propagation? Here I think the virtues are few and far between. Lets have a look…
Pure Intentions
Although we may not consciously think about it, I think there’s a natural tendency to see water as clean and pure, and soil as dirty and, well, soiled. When you take a cutting, you severe its connection with its primary life force: water. So it’s natural to feel an easing of anxiety by immediately dropping it into some nice cool, crystal-clear water. Gulp, gulp. Now you can breathe again. Easy.
Putting a cutting that, by definition, has no roots into water appeals to our intuition. After all, the cutting has damaged tissue, so do we really want to put that rootless, injured stem into living soil full of fungi, bacteria, and viruses? What is soil going to do for a plant that has no roots, other than rot? In water, not only might it grow roots, but it looks pleasing in the meantime.
All said, water seems like the perfect intermediary: sustaining life from the moment of the cutting (no roots) to the time of planting (with roots). Unfortunately, things are not quite this simple.
A few months back, one of my favourite houseplant people on Instagram (see Tony Le-Britton’s page here) put up a post suggesting why you shouldn’t propagate your cuttings in water. Whoa dude!, I thought, knowing the backlash that would soon follow. Partly due to the reasons mentioned above, and partly because of its ease and success, water propagation is very popular these days, and widely embraced in articles online. Countering this, Le-Britton suggested abandoning water cuttings, which he attributed to a general hesitancy to propagate directly in soil and a misconception that establishing roots first in water somehow made the transition more likely to succeed.
And yes, some of his Instagram followers complained (the post had at the time of this writing, almost 400 comments). Here’s one I found that summed up many of the others:
This comment brings up several issues. First, the author seems to be quite knowledgeable, so the appearance of expertise won’t help decide this, for the original post was from an ‘expert’ as well. Second, the comment makes it clear that this can be a very complicated matter if we want to make it one. I hope not to.
Third, the author makes it clear, in agreement with the original post, that not all popular houseplants can produce roots in water. For example, whereas some leaf cuttings (with no stem) will actually produce roots in water, a subset of these species will never actually produce a new shoot ever, whether kept in water, or planted with the roots.
Despite all this, I think Le-Britton’s post is right on the money. With a bit of clarification and a bit of argument, I think in the end we’ll all agree.
Show It or Grow It?
The first point of clarification is this: do you want to show it, or grow it? Or both? Maybe part of your desire to propagate a houseplant cutting is to also to have a nice specimen hanging around your home (sipping water). Or maybe you don’t care a whit about propagation; you just want to see plants in water, and watch them grow. (I had a Red-Anderson philodendron growing in a bucket in the bath for two years; the leaves grew smaller and smaller, but I thought it was cool.) In either of these instances, then, the answer is clear: water cuttings are great, just make sure the cutting is a suitable candidate for the job.
On the other hand, and this is where things get dirty, maybe we put cuttings in water with the specific goal of placing them in pots later on. This is where we are confronted by the critique offered in Le-Britton’s post, which is basically this: if your primary goal is to propagate, skip a step and go straight to substrate. The author is trying to help people out, knowing as he does that, from his own experience with valuable plants, water only adds a step; it rarely adds anything else to the process.
Why Le-Britton’s critique generates a lot of reaction is, I think, because it’s incomplete. Maybe it’s a bit too nuanced for an Instagram post.
A Pleasing Look of Success
One common argument in favour of water cuttings is that the person doesn’t feel confident in going straight to substrate. If you do something and it works, stress free, there’s no reason to change. Indeed. But as you carry on doing this, you might consider doing one or two little experiments on the side. If you’ve got a dozen Pothos cuttings, try a few in a mix (following the advice below) — you’ve got nothing to lose.
Here, if interested, is an in-depth YouTube video on the “science of cuttings“, no water necessary.
The video above reminds us of something important: throughout the world, hundreds of millions of houseplants are propagated via cuttings at plant nurseries every year, and these nurseries do not grow cuttings in water. The two nurseries below are in New Zealand and they grow houseplants in the thousands from cuttings. Watering is essential, but never are the plants first put in water to root.
Yes, it’s true that these are professional operations with special gear. But the point I’m making is the one made by Le-Britton’s Instagram post, which is that, horticulturally speaking, the water step is an unnecessary one. Plants do great going straight to substrate, given some precautions are taken, especially with regard to very free draining soils and high humidity.
So what about amateurs? For this I thought I might ask the houseplant expert, by which I mean D. G. Hessayon, whose first edition of “The House Plant Expert” appeared in 1961. Hessayon’s plant books were best-sellers for years because the books presented information with great authority (Hessayon had a BS degree in botany from Leeds University and later earned a Ph.D. in soil ecology).
I liked the idea of asking Hessayon because, as noted, the book is tailored towards the amateur, not the professional; I also knew it had a chapter on propagation. So then, what does this expert say about the amateur doing water cuttings? Well, alas, he says nothing at all. He covers simple and complex methods like division and air-layering, and he has a tidy section on propagation via different kinds of cuttings, and different methods of rooting them. But again, nothing on water cuttings.
If your primary interest is in propagation, going straight to a medium that can support new roots as they emerge is best.
Root Bound
The advantage of placing cuttings in a soil mix is not only that it skips a step, but it also has the right environment waiting as the roots arrive. But will they arrive? There is a certain truth in the belief that water provides hydration that the soil cannot, given the initial absence of roots. There are three points to be made here.
The first is made nicely by the Laidback Gardener, who writes, “The problem is that the roots produced on a cutting started in water acclimate to an aquatic environment. When you later transplant the cutting to a pot, the aquatic roots die and rot, forcing the young plant to start from scratch and produce a new set of roots. Often, it no longer has enough energy for that and dies. So to ensure good rooting success, I suggest you always start your cuttings directly in some sort of substrate such as potting soil.” This is why I call water roots ‘confidence roots’, because they give us confidence to pot them up.
It’s also worth adding here that many types of plants will secrete their own growth hormones when cut, but these hormones will become ineffective as they dissolve in water.
The second point is that soil mediums do offer something that roots need and that water doesn’t supply very well: oxygen. When placing a cutting in water, we have solved one problem (plenty of water) but created another (shortage of oxygen). As we would expect, having been told a thousand times not to overwater our plants, how well oxygen diffuses into soil depends largely on the soil/water ratio. In other words, water-saturated soils suffocate the roots. This is why plants (and fish) in fishtanks have aeration, and why houseplant cuttings put in water have oxygen in short supply. This is demonstrated in experimental studies such as this one, which examined the effect of aeration on plant roots. The report concludes:
Pea roots in water cultures were subjected to different aeration conditions. Root elongation and root branching were strongly affected by the air supply, elongation being favored by increasing aeration and branching activity by decreasing aeration. By changing the aeration conditions from full aeration to no aeration and vice versa it was shown that the extent of root elongation depends on the availability of oxygen. … The formative influence of oxygen on root branching is characterized by a greatly enhanced root density due to a higher number of laterals per unit root length producing them and accelerated development of laterals of a higher order.
My third point is perhaps most important, given that many do have success in water cuttings with some types of plants. Just as water provides hydration, efforts need to be taken to be sure that, when not using water, hydration still happens (and rot doesn’t). To do this on a small scale you can simply use a clear plastic container with a lid that seals, sized according to the number of cuttings and their height.
Often when doing this I use a half/half combination of pumice and a chunky potting mix, and usually the mix has enough moisture out of the bag that you need only lightly wet the top surface with a spray bottle once the cuttings are placed.
You do not want wet soil and regular potting mix will easily become too wet if you add water. If the box gets a bit of direct sun, the humidity may escape the soil quite a bit in some areas of the box, so a light watering of these areas might be needed later on (read the beginning of this Dirt Wise post for more on this).
In addition to this, it’s common practice to dip the cutting into hormone powder, although not all plants need this (a Google search by species will help you narrow it down). With that done, as necessary, all you have to do is wait some weeks, depending on the time of year, and you’ll have a pleasing result.
Pot Up!
In closing, let me stress again that doing cuttings in water is neither right nor wrong: it all depends on what your objectives are. If you do have a go with propagating some babies in soil, I think you’ll find that there’s a real pleasure in the outcome. Lifting well-rooted cuttings out of prop boxes allows you to create new plants and thus see how to put nature to work.