Granted, autumn isn't the best time for cuttings. They generally root better in spring, when both plants and people are full of vim and vigor and raring to go.
However, I have to prune my potted tropicals in autumn, so they will fit under my grow lights over the winter months. And I hate to waste the snipped-off tips. So I stuff them into fruit juice glasses or jelly jars which have a little water in the bottom and set them on a windowsill. A surprising number of cuttings will root that way.
Some gardeners call the roots which form with this method "water roots," and claim that they aren’t as dependable as roots which have started in soil. I’ve never seen much difference, myself. But, if someone sends me unrooted cuttings of a plant I don’t have, I generally will root those in a sterile mix with rooting hormone--just to be on the safe side.
With cuttings of plants that I already possess, I’m lazier. After rooting those on my windowsill, I generally pass them on to other gardeners if I can, either as trades or gifts. Of course, trying to give away extra plants during winter can be much like trying to give away extra kittens or puppies. If you do it too often, your friends and family members may look wary every time they see you coming!
Actually, I have cuttings rooting on my windowsill throughout most of the year, since I stick twigs which have gotten accidentally broken off into the glasses too. Just now, I also have pieces of my 'Chicago Hardy' fig standing in water, as I had to cut the tree back before covering it for the winter. Our south-facing windowsills work well for rooting because the house’s broad eaves ensure that those windowsills get only bright, indirect light during spring and summer. That's the type of light usually recommended for cuttings during those seasons.
They don’t seem to mind direct rays in autumn and winter, when the sun is low enough in the south to penetrate beneath our eaves. In fact, I suspect sun during the cooler seasons helps the cuttings root by warming the water.
If you want to try this, any small glass containers--such as the aforementioned juice glasses or jelly jars--usually will work. Rooting jars offered in catalogs often are made of colored glass, but the tint isn’t necessary unless you need to do your rooting on a sunny windowsill during summer, when the color may block out some of the sun and help prevent the roots from overheating. Of course, my originally transparent glass often builds up a greenish-tint of its own, probably due to algae, but that doesn’t seem to affect the rooting.
Keep the water in the containers shallow--about an inch or so deep, covering at least the lowest leaf node on each cutting. When you water your plants each day, replace any water which has evaporated.
I usually strip buds and lower leaves off the cuttings--and snip the base of each at an angle just beneath what had been a leaf joint--before placing the cuttings in the glasses. (For those with very large leaves, I may snip off the outer half of each leaf too, as you don’t want the cuttings to have to support much foliage while rooting.
It's best to allow those which have white “blood,” such as euphorbia and ficus, to dry for a few hours before you stick them in the container. For African violets or other fuzzy plants that rot easily, you probably will need to use the covered jar method instead--with holes punched in that covering. (I generally use aluminum foil for the covering.) In that, case, of course, the glass needs to be fuller.
Plants which I have rooted in water include: abutilon, brugmansia, clerodendrum, coleus, euphorbia (crown of thorns), ficus, fuchsia, (tropical) hibiscus, impatiens, pelargonium, and thunbergia--among others. I wouldn’t attempt this with cacti cuttings, many of which need to be dried to form a callus before they will root. Some succulents require that treatment as well, but others aren’t as picky. For example, a couple cuttings of lemon vine (Pereskia aculeata) recently rooted easily. Some plants, such as kalanchoes, may obligingly make their own extra roots at the joints as they are growing. So, when they become leggy, you can cut them up and re-pot them easily with no additional rooting required.
Every week or so, I sort through the cuttings and throw out the shriveled ones, while also removing any dead leaves which may have fallen into the water. Don’t assume that a cutting has expired just because it has dropped some or all of its leaves. If the stem still is green, the cutting still is alive and may root. Once it does so--and leafs out again--you need only pot it up and slap a ribbon on that pot to turn it into a gift!
Photos: The photo of rooting African violet leaves is by Rachel James, courtesy of Flickr Creative Commons and this license. The other photos, including the banner image, are my own.