Different techniques for taking starts from plants, and how to make them work in a greenhouse setting
I like to think of a plant-free lawn like a blank canvas, albeit a green one, just waiting for me to add a little color here and a touch of texture there. Sadly, unlike in my imagination, in the real world all those weigela, spirea and butterfly bushes cost money—the bigger the lawn, the bigger the bill. As it turns out, other gardeners have this same problem, but if we put our heads and plants together, we can all have beautiful landscaping at a fraction of the cost.
Before you ask, I’m not talking about a black-clad midnight robbery of the local nursery, although we can call that Plan B. What I’m suggesting is much easier, completely legal and just one way you can use your greenhouse to further your passion for growing without breaking the bank. So many of our favorite landscape plants are easily propagated from cuttings that if you and a few friends comb the neighborhood for the plants you’re craving, you’ll fill your greenhouse in no time.
Making the cuttings
There are several different types of cuttings you can take, depending on the kind of plant and the time of year you’re cutting. Some plants take better from certain stages of cuttings—as a general rule, deciduous shrubs take best from softwood cuttings, broad-leafed evergreens from semi-hardwood cuttings and narrow-leafed evergreens (and some deciduous shrubs) from hardwood cuttings.
Softwood cuttings are taken in late spring or early summer from vigorous shoots that are beginning to mature, but are still relatively green. Take four to six inches from plants you’d like to propagate, in the morning or after a rain. Always keep cuttings moist for the best results.
Semi-hardwood cuttings are taken in late summer, from shoots that are from the current season’s growth and are becoming woody. These six-inch cuttings will be less green than softwood cuttings and may have a good number of leaves. Make sure to peel the leaves and buds from the bottom half of the cutting before attempting to root them.
Hardwood cuttings are taken from mature wood in the late fall or winter, after the first hard frost. Only the younger shoots should be considered for cuttings, you should never try to root thick, old growth. When cutting, you’ll need eight to 12 inches of the shoot—if you can nab some year-old wood, so much the better. Work quickly, the cold weather can easily damage these young shoots and dry them out.
Herbaceous cuttings are another thing entirely—they’re made from live parts of tender plants like mint or African violets. Take these cuttings whenever you’re in the mood and the plant is growing vigorously, but keep the cuttings moist or they will die before taking root.
Turning your sticks into plants
Once you’ve got your cuttings collected, you’re ready to use your greenhouse for one of the things it does best—propagating! Select pots that are large enough for the plants you intend to propagate to grow unhindered until your local conditions are ideal for planting—quart-sized pots are usually a pretty good choice for landscape shrubs. Fill your pots with a soft-textured, easy to wet, sterile medium. That last part is really important. Don’t try to start your young, clean plants in old dirty soil—there’s too much risk of introducing pests and disease with old medium.
Peat is a popular favorite, and although the texture is light, I find that it’s way too hard to wet. On the other hand, peat is cheap, so I generally mix it with an equal amount of coconut coir, by volume, to make wetting easier and keep costs down. Other growers mix in up to 25 percent perlite or vermiculite—these are fine rooting mediums in their own rights, too, if you’re able to water them frequently. No matter what medium you choose, make sure it’s moist, not wet, before you begin potting.
Moisture is the key to success with cuttings—these little plants have suddenly gone into ultra-stress mode and are scrambling to put out new roots. They’re drawing on food reserves, so don’t worry about fertilizer (in fact, hold back on fertilizers for a while or you’ll add to the drama), but water every day if necessary.
If your greenhouse is capable of maintaining a high level of humidity, in the 80 percent or greater range, you may be able to get away with less frequent waterings, but check your cuttings daily and water any time the medium isn’t moist to the touch. It’s tempting to shortcut the daily waterings by sitting your pots in saucers, but trust me, this is a bad idea. Your cuttings need moisture, without a doubt, but leaving them soggy will end in root rot and despair. Water them the old-fashioned way and let them drain.
What about rooting hormone?
The jury’s out on rooting hormone in general, though some plants seem to respond better to it than others. If it makes you feel good to dust your plants with rooting hormone, go for it—it won’t hurt anything. An even better idea is to dust them with a little powdered sulfur to help prevent fungal disease from developing while the new roots are forming.
With or without rooting hormone, the process is a slow one, so be patient and keep watering. Some species can take months to set proper roots, but you’ll know when it has finally happened because your sticks will suddenly start growing and putting out new leaves. At this point, you can give them a little balanced fertilizer and allow the top of the medium to dry completely between waterings.
I usually set up a different area for rooted plants so they can breathe a little and I can tell which plants need what sort of treatment. If your greenhouse allows for multiple climate zones, this is the time to start gradually moving your rooted plants to an area with decreased humidity. Start by taking them out of the high humidity area a few hours at a time, then all day and after a few weeks, leave them in a lower humidity area permanently. I know it seems like a lot of work, but by moving them into a lower humidity zone, you’re decreasing the risk of disease and getting them ready for the environment they will find outdoors.
All that’s left once your sticks are leafing out is to move them to the landscape, after a properly slow period of hardening off. You may end up with many more successfully rooted cuttings than you needed, but don’t worry: your friends, family and neighbors will happily take the young, healthy plants off your hands. The next time they’re dividing perennials, they’ll think of you first and before you know it, your work in the greenhouse will have created the landscape you always dreamed of out of nothing but sticks and dirt.