Why cuttings fail
I asked other growers and combed through weighty tomes on plant propagation. I searched the Internet and chatted up strangers at nurseries. Determined to grow healthy cuttings, I finally found success after repeated failures and a bushel of research.
That natural process which interferes with cutting growth, is rotting, which happens much more often than rooting. If every twig that dropped to the ground started to root, we'd have no compost and no way for dying plants to return their nutrients back to the soil!
So to root, you must avoid rot. Sterile conditions are rot's biggest enemy. You will prepare your cuttings with sterile tools, in a sterile environment, set them in a sterile medium and discourage the growth of bacteria and fungi that promote rot.
The other big reason cuttings fail is lack of water. A real plant has roots that dig down into the soil and gather water. A cutting, having no roots has no normal way to gather water. You must keep it standing constantly in a soggy medium, in a high-humidity environment. Professional growers have greenhouses to maintain the high humidity; home growers need to create miniature greenhouses for their cuttings.
And guess what all that soggy medium and humid air promote? Rot, again. Mold, fungi and bacteria are just waiting to devour your little cutting. But if you can keep it both soggy and sterile, your chances for success are great.
So why does a little coleus cutting root in an ordinary glass of water with no attempts made to sterilize its environment? Why can you pop a
fuchsia into a pot of soil and just stand back and watch? That's because coleus, a member of the mint family, propagates naturally from underground, rot-resistant stems. Some plants are just like that -- rooting
in spite of nature's attempts to break them down into compost. Once, I threw Fuchsia
prunings onto my steaming compost pile and discover them growing beautiful flowers a few months later in spite of the concentrated heat and decomposition bacteria in the pile. And many familiar weeds of course are notorious at re-sprouting.
Collecting your cuttings
Take any reasonably clean container, such as a pitcher or plastic bag and fill with in inch of water. This is your collecting container. Take a reasonably clean pair of scissors into the garden and gather your cuttings. Your best results come from fresh, young tip growth. Cut off all but one or two leaves and make sure a few leaf nodes remain on each stem. Your cuttings will end up being about 4 to 6 inches long, but for now you can cut them eight to twelve inches just to get pieces that are easy to work with.
When visiting parks or friends' gardens, get in the habit of taking folding scissors and a
zip lock bag with a bit of water trapped inside as your collecting container. Look forward to starting your moist cuttings when you get them back home.
Selecting Growing Containers
Cuttings have been grown in pots, fishbowls and orange crates. The trick is to use a container where you can easily change the water, and still keep the cutting covered to preserve the high humidity. I like to use plastic storage bins, or self-watering pots, or a wick-water a container with
capillary matting. Some people cover ordinary pots with plastic bags, using sticks to hold the bags up and away from the cutting. The cutting should never touch the sides or cover of the container.
One interesting idea is to use the jiffy seven peat pots inside plastic bags. Growers suspend the little bags under their
fluorescent lights. Those square peat pots you buy at garden centers aren't suitable though; they dry out quickly.
Another method is to place a large pot with ample drainage holes in a saucer of frequently-changed water, cover with plastic wrap and keep in a shady section of the yard.
Growing medium
Whole Ph.D. thesis have been devoted to this topic! Most growers use vermiculite, perlite, horticultural sand or a combination of these three. I find the sand drifts through drainage holes and perlite is too dusty, so I prefer vermiculite. Never use soil, even bagged potting soil as it isn't sterile. Water isn't recommended as a growing medium either, despite the fact that your grandma rooted her cuttings in water. Most growers believe that water roots are wimpy and don't help a plant stand sturdily upright in soil when it is later transplanted. Also the strong roots formed by pushing through vermiculite will help your plant thrive in harder packed garden soil.
I fill my containers with vermiculite, pouring it in to a depth of 2 to 3 inches. I water the vermiculite well until it no longer can hold water. If I am using a container without drainage holes, I'm especially careful to be sure no excess water remains but that the vermiculite is soggy through and through.
A sterile environment
Begin your adventure by mixing up a vat of nine parts water with one part chlorine bleach. This will be your sterilizing solution, divide it between several smaller buckets
which you've thoroughly washed in hot, soapy water. As you work, try to avoid reusing a bucket of solution. Wash everything first, with hot soapy water, then sterilize it by soaking briefly in your solution. If you have a dishwasher for cleaning your tools and containers, you can skip the hot soapy water step.
Clean your work surface and sterilize it. Work with disposable rubber gloves. Once something is sterile, don't contaminate it by inadvertently bringing it in contact with a dirty tool or cutting.
I start by rinsing the cuttings off with cold water, then dumping all the cuttings into a bucket of the sterile solution, swishing them around a bit and piling them on my already sterile work surface. I then discard the solution in that bucket. In another bucket I sterilize a sharp clean knife.
Using the knife, I cut each stem right below a leaf node at a DG45 angle, exposing as much growing surface as possible. The new roots will form from the leaf node. Don't make your cut above the leaf node because the cutting will die back to the next leaf node anyway.
Also, make sure the little cutting only has a single leaf, or two small leaves to support. If there is extra non-essential growth remaining it will
unnecessarily stress the little cutting which hasn't got a way to gather water to keep its extra growth alive. Trim off extra leaves, thorns and
branch-lettes. You want a slender, fresh young stem which will put all of its growing energy into roots. It should bee from four to six inches long.
Growers differ in their preference for rooting hormone, a white powder you can buy at any garden supply store. You can dip each cutting in a small amount of rooting hormone, or forget this optional step. I find that thick woody stems, like those on roses benefit from rooting hormone whereas soft fleshy stems, like those on tropical houseplants don't need it.
Using a chopstick, I punch a hole in my vermiculite and carefully set the cutting into the hole, tapping the vermiculite firmly around it. I sprinkle it with a few drops of water because I don't want to risk it drying out even a bit. If I'm working with a large batch of cuttings, I'll also mist the pile frequently to keep everything moist.
When you finish, cover your container immediately with something transparent and set it in bright,
diffuse light. Outside bright or deep shade is fine, inside, place in a bright windowsill or under
fluorescent lights. Cuttings won't thrive in sunlight or darkness. Under fluorescents, make sure bulbs are suspended six to
twelve inches above the cuttings. Unlike starting seeds, cuttings don't require your best light. The more light they receive however, the faster they'll root. Keep them at a comfortable room temperature, or slightly warmer than you prefer -- think of warm, tropical jungles. Don't expose them to drafts or freezing temperatures or baking sunlight, or prolonged dark but don't worry if light or temperature isn't optimal, either.
Change water frequently. I like to add a drop of chlorine bleach to water I'm giving my cuttings. In wick-watered containers, I change water once a week. If any cutting develops signs of rot, such as mold, I remove it immediately. I also remove any dying plant material so there's nothing for
fungi to feed on.
Don't fertilize cuttings
You should only feed plants that are in active growth anyway, and we want our
cuttings to concentrate on growing roots. As roots do begin to form fertilizer, or a lack of sterility will become less harmful.
How long will it take? I once read that rhododendrons take two years to root. Some houseplants start rooting in three weeks. A more average time is three to four months. If light is dim and temperatures are lower, it will take longer, but roots can still be very healthy. I once rooted rose cuttings in six months in a cold, north-facing back bedroom. I rooted Rosemary under bright
fluorescents in summer in six weeks. Both the roses and the rosemary thrived.
When is it ready
When roots grow, of course. You will suspect roots have formed when the cutting begins to produce new growth, but you can gently tug on a cutting to check. New roots are
delicate, but handling a cutting carefully, and replacing it by poking a hole in the vermiculite will prevent injury. When roots are three inches or longer, the cutting can be repotted to a pot with potting soil. Continue to water cuttings regularly after repotting as their roots are still underdeveloped and mist them frequently or keep them covered part of the time so they make a gradual transition out of high into your normal humidity. They should be gradually hardened off, or accustomed to your lower garden humidity, less frequent watering, or lower room temperatures and ordinary soil. Sudden changes will kill the
new, little plant.
