Propagating Houseplants

Apr 03, 2014

The long winter finally seems to be loosening its grip and allowing for some warmer weather to move in, melt the snow and warm a gardener's heart in anticipation of what might be grown this year. However, it will still be a few weeks before we can start doing much gardening outside. We are nearing the time to start those tomato, pepper and other vegetable seeds but it's better to wait a little longer yet, instead of jumping the gun and ending up with overgrown transplants at planting time. If you still want to start growing something now, how about propagating a few houseplants to get green thumbs working and renew some of those old plants with fresh starts for your windowsill. Written by David Graper, SDSU Extension Horticulture Specialist and Director of McCrory Gardens.

Most of our common houseplants can be propagated by using cuttings, usually taken from the top 2-3" of a stem. These are called tip cuttings. You can also take more cuttings from lower down on the stem. For many plants you can take single-node cuttings but just cutting the stem above and below where the leaves are attached to the stem. And, some plants, like begonias, African violets and peperomias can be propagated by leaf cuttings. What you'll need Before you get started you will need a few supplies. Six-inch pots work well as a container. They can hold several cuttings and are a good size that will fit on a windowsill or under a grow light. You can also use cell packs, flats or even egg cartons.

Ideally the container should be at least 2-inches deep to allow for enough media to hold up the cuttings. You will also need some sort of propagating media. My favorites are perlite, a mixture of 50:50 perlite and peat moss or a commercially prepared peat-lite propagation media. I also recommend using a rooting powder. It contains plant hormones that will help to stimulate root formation. These should all be available at your local garden center or discount outlet store. Many people have probably rooted cuttings by just sticking them in a glass of water. I remember rooting geraniums like this back when I was just starting to garden. My mother always kept some geraniums on the windowsills over the winter so this was the way that we started new ones for the summer garden.

This method will work for lots of plants but I think you will find that you will have much better success with a wider variety of plants if you use a rooting media instead of water. The roots that are formed in a rooting media will be more vigorous and better adapted to growing in regular potting soil than those that form in water. Choose the propagating media and containers you want to use. If the containers are used, clean them before using. Soaking them in a 10 percent bleach solution for about 10 minutes will also disinfect them and give you a better chance of success. Add warm water to the media and mix thoroughly so that it is moist but not dripping wet. Warm water will work better than cold water if the media is really dry. Loosely fill the container and firm slightly.

Use a pencil or dowel to make holes about 2-inches apart and 2-inches deep in the media. You should be able to get about six cuttings in a six-inch pot, depending on the size of the cuttings. Use a sharp knife or sharp pruning shears to collect your cuttings. Generally smaller cuttings, 2-3-inches long with two to five leaves will work better than longer cuttings with a lot more leaves. If the cuttings are too long and have too many leaves, they are more likely to wilt and die before they have a chance to produce new roots. In most cases it is also a good idea to remove the bottom leaf or two so that you will have at least one node, the point along the stem where the leaves are attached, under the propagation media. Roots most often form at the node or along the stem, close to the node. Dump a small amount of the rooting powder onto a paper towel or other surface then dip the cut surface into the powder. You don't need to put on a lot of the rooting powder; a small amount on the cut surface is probably all you need. Now, carefully insert the cutting into one of the holes you prepared in the rooting media. Repeat the process with additional cuttings. You can mix cuttings of different plants together in the same pot if you wish; you will be taking them out and repotting them after they have rooted anyway.

Once you have your pot or container filled with cuttings, give them a good, gentle watering to saturate the media and help to firm it around the stems of the cuttings. One of the most important steps in cutting propagation is to provide a humid environment around the cuttings to prevent them from drying out. Now that you have removed them from the parent plant, they have no way of taking up water. So, you have to keep the humidity up near 90 percent so the cuttings stay turgid or full of water. The easiest way to do this is to just cover the pot and cuttings with a plastic bag. The bag will help to contain the humidity released by the propagation media and the cuttings, allowing them time to form new roots and start growing. You should see some condensation form on the inside of the bag, but if it looks like it is getting too wet in there, you may want to open the bag up a bit or cut some holes in it to allow for some fresh air to get inside.

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