In early autumn, making your own topiary trees from cuttings taken from the garden is one of the most rewarding projects for a gardener. Shortly before frost arrives, cuttings from lavender, rosemary, scented geranium, woody thyme or fragrant myrtle can be rooted and then trained throughout winter into a treasured topiary.
It may take some time, so patience will be required if you want to enjoy displaying a set of perfectly trained, homegrown topiaries by next Christmas, but the time to start is now — besides, growing and training them is the best part! Here is how you can do it yourself at very little cost, aside from time.
Choosing the best herbs to train indoors
The truth is few herbs make good indoor potted plant subjects, but with a little clever forethought, most everyone can train a topiary, as long as you know the tricks.
Many plants, even some that look like herbs but are not, make terrific topiary specimens, so be creative. I would avoid using tender, annual herbs such as mint or basil. You will need your plants to form strong, woody stems, and to be able to take a hard trim every now and then.
Look for woody herbs such as rosemary, thyme, lavender and myrtle. Bay laurel is an excellent choice for a large topiary but will take many more years to mature, and they can reach great heights. The art of topiary is very similar to that of bonsai, you will be trimming and training a plant to stay within a particular shape.
Once you have selected the best plant material (which you will base on what you can logically grow well in you home or garden), then it’s time to start loads of cuttings.
1. Take cuttings when growth has begun to slow down and the green wood is beginning to mature.
Take 4-inch cuttings from your outdoor plants, but avoid woody stems because roots will form on hard, green stems better than on woody stems. Strip the leaves off of the bottom third of the stem. Then make a sharp cut at an angle with a razor or a sharp knife to ensure a clean cut, which will be less likely to decay in the rooting medium. Many summer herbs will root easily in autumn, such as lemon geranium, rosemary and myrtle.
2. Prepare a rooting medium and a tray for your cuttings.
Cuttings need a sterile rooting medium, which can be made with 50 percent sharp builders’ sand and either 50 percent perlite or 50 percent vermiculite. You can use all sand if you wish, but the sand must be coarse — but not so coarse that it will dry out too quickly, like pool sand. The medium should retain moisture. Water the medium once, and allow it to drain well before placing prepared cuttings into it.
3. Place prepared cuttings into the rooting tray.
Herb cuttings will root more quickly if you dip the prepared bottom part of the stem into a rooting hormone. This is especially true if you have woodier stems, but most will root fine without hormones — they just may take longer. The greatest challenge indoors will be keeping the relative humidity high around your cuttings. Placing the entire tray into a dry cleaner bag or a clear plastic bag will help. Check your cuttings weekly for roots, which should from within three weeks.
4. Pot rooted cuttings into pots to begin training after a few weeks.
After your cuttings have rooted, carefully remove them from the rooting tray, and pot them in 3- or 4-inch pots using a good commercial potting soil. Place a small yet tall bamboo cane into each pot as near to the stem as possible.
There are two mistakes people often make when training a topiary. The first one is the tying material. Avoid wire because it can cut a stem as it grows. The best choice is raffia, which can be found at craft stores (make certain that it is not synthetic, however). Dampen the raffia and then tie a stem to a cane tightly. It won’t damage the stem.
The second trick is to not remove the bottom leaves on your topiary until the plant is well established, as it will need every leaf with which to photosynthesize. It will be tempting to strip the foliage from the bottom of your plant, but resist until the plant is 12 to 18 inches tall.
5. Choose the shape in which you want to train your topiary.
You can choose from many shapes into which to train a topiary tree, from standard (traditional lollypop shapes) to pompom (triple ball towers), to long, slender cones, spirals or even wreath shapes if the cuttings grow along a bent wire coat hanger. There is no shortage of online reference material that can inspire you, but don’t be afraid to experiment. The window boxes above show how I have trained a miniature hedge of rosemary, inspired by the pleached (raised, woven) hornbeam hedges seen at Versailles in France. Eventually, a long, continuous hedge will be formed above a phalanx of little trunks.
Training is a skill that is not difficult to learn, nor to imagine. Simply keep tying your central leader to the bamboo cane until your plant reaches the height that you want, and then pinch out the growing point. Keep all foliage and suckers removed from the main stem up to the point where you want your form, usually the top 6 inches of the stem, which you will allow to grow. However, keep these side stems pinched closely, allowing a pair or two of leaves to form before pinching again. Keep this up at the beginning to ensure that an inner foundation of branches will be formed. Eventually, a shape will emerge, and a weekly ‘haircut’ will be all that is needed.
6. Trim frequently to create dense, tight growth.
You will need to become an expert pruner and hair stylist if you want to raise perfectly tight and dense growth on your topiary trees, but this is the “art” part of topiary craft, which means that it is the fun part. Use sharp scissors to trim herbs, and trim closer than you normally would, especially in the low light of winter. The goal is to stimulate tight, dense growth. Every time you snip and trim, side branches will form, which will make your spheres and forms more in character. Start young, and trim often rather than pinching the main leader out and then waiting for your side stems to grow long.
7. Herb topiaries grow well as outdoor container plants.
A display of topiaries outdoors is proof that a capable gardener lives in the house. When grown indoors, rosemary, thyme and lavender can be difficult if your house is warm, as the dry, heated indoor conditions of winter can prove fatal to these cool-loving plants. Best results will be had if you have a cold, bright room such as an unheated bedroom window, a sunny garage or a cellar window where they can spend most of their time.
Return topiary herbs to more temperate rooms for brief display periods only, and then return them to their cool, growing rooms after a few days. This will keep them fresh and free from the problems that a hot, dry interior will present (rosemary will simply not survive in a typical indoor winter climate). Find clever spots for them near your coldest windows. Never allow herbs to completely dry out in the winter, as missing just one watering can prove fatal. Display pots on a tray of gravel for best results.
It can take up to 18 months for a cutting from a rosemary or a myrtle to transform into a gorgeous topiary, but you have options — plants like many scented geraniums grow quickly, and can grow into a topiary in just 3-4 months.
Photo credits: Matt Mattus
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