How to prune miniature trees

The basics of pruning
The dwarf mugo after pinching the candles off.
Pat Hayward
Judicious pruning turns a miniature lemon-scented geranium into a colorful shade tree along the Rio Verde Western Railway of Larry and Tanya Rose in La Mesa, California.
Pat Hayward
Sharp pruners, such as these by Felco, make pruning jobs go smoothly. By setting the newly purchased plant up high, it's easier to see exactly where to cut on this dwarf yaupon holly (Ilex vomitoria ?Beehive').
Pat Hayward
Pines, such as this dwarf mugo (Pinus mugo ?Mops') should be "pinched" while in the springtime "candle" stage.
Pat Hayward
The candles can be shortened to any desired height, and should be pinched just before the needles elongate.
Pat Hayward
I learned the scientific theories of pruning in a college class called "Landscape maintenance techniques," but I learned the art of pruning from Larry Watson, a nurseryman I worked for, who'd been pruning trees for more than half his life. About once a month he'd take a group of us out to the fields, choosing a different type of tree each time. We'd talk about how each species of tree grew naturally and then discuss its response to pruning. After demonstrating on a couple of trees, he'd let us each try our hand at it. We did this for a couple of years, learning the differences between pruning oaks, maples, pines, spruce, and ash trees. Over time we were able to see the results of our efforts, learning what worked best for each tree species. Larry, like all good teachers, knew this was the best way to learn-first by understanding, next by doing, and then by observing our results.

You don't need to go to these lengths to learn how to prune plants on your outdoor railroad, however, because pruning plants is pretty easy once you understand a few basic plant concepts. First, plants are living things and respond to pruning in fairly predictable ways. The second rule is that no matter how much you know about pruning, plants are living things and often respond to pruning in very unpredictable ways. But not to worry; the two great things about pruning are that it's hard to actually kill a plant by pruning it (at least in moderation) and even the worst mistakes can often be corrected.

This is what happens when you cut a stem or branch of a tree. Normally, most of the plant's energy is directed to the tip of the stem (a process officially called "terminal growth"). Removing the tip (or terminal) of the branch diverts the energy back along the stem to its side ("lateral") buds. Don't worry if you can't see these side buds-they're usually either very small or invisible ("latent") to the human eye. In essence, removing the tips of branches actually creates bushier, denser plants because it re-directs all the energy that would have gone to a few tip buds to the side buds instead.

Pruning also allows you to control the direction of new growth. If you've ever grown hybrid tea roses, you know that the normal rule is to keep the center of the bush relatively open to discourage insects and diseases. This is achieved by pruning to what's called an "outside bud," meaning that you need to find a bud pointing to the outside (rather than the inside) of the plant and prune the stem just above that bud. This redirects the energy to this "outside" bud, resulting in a new branch that will grow outward.

Thinning a tree or shrub to make it look more natural in the railroad landscape is a slightly different matter. As branches grow older, their latent buds become less active and less able to kick into action when the terminal buds are removed. This explains how you can cut a larger branch all the way back to a main tree trunk and not end up with mass of new growth at the pruning site, though this does happen on occasion.

Pruning conifers is just a bit more complicated than pruning deciduous shrubs. Spruce trees, such as Alberta spruce, are generally easy to shape through pruning because they have very active lateral buds. Chamaecyparis (false cypress), junipers, and yews also have active lateral buds.
Pines react differently to pruning because their buds are much less active than those of spruce. In fact, once the needles have dropped from a pine branch, it's unlikely you'll get the tree to sprout on that branch again. It's best to control pines when they're actively growing, at what's called the "candle" stage. A candle is the new tip growth of the pine, just before the needles start to stretch out. If you want to control the size of a pine, simply pinch out the tip of the candle, leaving as much or as little of the new growth as you want to remain on the tree. You can even remove the entire candle if you don't want the pine to grow at all that year. It's also better to "pinch" pine candles instead of pruning them with cutters, because metal tools can easily injure new pine needles and may result in burning or die-back on those needles.

After all is said and done, pruning is as much an art as it is a science. And, like any form of art, it takes lots of practice. Start with some inexpensive plants before you tackle bigger or more costly projects. Have specific goals in mind and experiment with different techniques. And just as professional woodworkers follow the adage "measure twice, cut once," make doubly sure to remove only the branches you mean to.

Pruning terms to remember

Candle. The new growth of a pine, just before the needles elongate

Lateral bud. Bud growing along the side of the branch, usually at the base of a leaf or a needle

Latent bud. Dormant or inactive bud, often invisible to the eye

Pinching. Removing unwanted, soft new growth with your fingertips

Terminal growth. The plant process in which most of the plant's energy is directed toward the (terminal) buds at the tip of the branch
Pruning Q&A
Q: When's the best time to prune trees in the garden railroad?

A: Every time you make a cut on a plant, you're actually encouraging latent buds to grow. With that in mind, it's best not to encourage new growth in late summer or fall in areas with cold winters. Most plants can be pruned in the winter, spring or early summer and recover quite nicely. If you want blossoms on your spring-blooming shrubs and trees (such as dwarf lilacs or spireas), it's best to prune them right after they bloom. If you prune spring-blooming plants in the summer, you're likely to prune off buds for next year's flowers. In warmer climates you can prune plants just about any time they're actively growing.

Q: Every winter my Alberta spruce burn on the south side. Should I prune out the dead parts?

A: In some parts of the country (particularly in the southwest, where there's bright sunshine, lots of wind, and low moisture in winter), many conifers, including Alberta spruce, will often show signs of "sunburn." It's best to wait until later in the spring to do any pruning on these trees. In many cases, the latent buds will soon leaf out and fill in the dead-looking areas. If those areas fail to leaf out, use this as an opportunity to create more open, natural-looking forest trees.

Q: Every summer spider mites practically defoliate my Alberta spruce. Should I prune out the dead-looking parts?

A: Spider mites are a serious problem on Alberta spruce in hot climates because rising temperatures increase the mites' rate of reproduction! Keeping your trees and the areas around them clean of dead needles is perhaps the best solution to reducing the mites' effects until the temperatures start to drop again. (This physically removes many of the mites and their eggs from the site.) Alberta spruce recover fairly quickly from needle loss, so wait to see what's really dead on the tree (as opposed to what just looks dead) before taking your pruners to them.

Q: What type of pruners should I use to trim my trees?

A: Any tool that you choose should be sharp-that's the first rule for making clean cuts that won't damage your plants. My advice is to buy one pair of really good pruners that you can use for all you pruning needs, from G-scale trees to normal-sized landscape plants. I use Felco pruners because they're high-quality tools that can be taken apart for cleaning and sharpening. Felco pruners come in several styles, including lighter weight models for women, a model with rotating handles, and even a version for left-handed people. I also like the idea of just one pair of pruners to handle every job in the garden-much easier to keep track of than several specialized tools.


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