The old folksong, Wild Mountain Thyme has in the chorus “We will all go together to pull wild mountain thyme.” We wince at that line because pulling the thyme will kill it. The Herbin’ League trio (a group of old-time folk musicians hailing from the Ozark Folk Center in Mountain View, Arkansas) changed the lyric to “…cut wild mountain thyme.” But some herb gardeners are afraid to do even a small amount of judicious pruning, often out of a fear that the plant will be harmed. Education is the key: Once we understand how plants function and the reasons for pruning, it is easier to sharpen the tools and get to work.
We harvest herbs during the growing season just as the flower buds are formed because the plant oils are at their peak. Deadheading flowers improves the look of ornamental plants and often extends the bloom time. If we are preserving annual and biennial herbs such as basil, chervil, cilantro, dill and parsley, we cut them before the plants flower. Whether pruning for harvest or plant health, we prune before autumn so new growth has time to harden off before a hard freeze.
Herbs need pruning for purposes other than human consumption, so don’t feel guilty. Diseases and pests are controlled with proper pruning techniques. We need to prune to control rampant growth or shape plants in a formal or stylized garden. Heavy pruning is best done in winter for deciduous plants and spring for evergreen plants. Avoid pruning herbs when new leaves are budding in spring or old leaves are falling off in autumn. It is best not to prune during times of drought.
Root pruning is performed on plants to increase health and vigor or to transplant from one location to another. We don’t do this all of the time or with all of our plants, but only when the plants need it. Overall, plant growth is always more vigorous in the spring, but roots of perennial plants are active year round. Pruning the roots when the soil is warm and deeply moist is the ideal condition for new root growth — not too cold nor too hot, and moist enough to sprout but not dry out. The idea of root pruning is to encourage the feeder roots to grow.
Visualize plant physiology
Plants have a vascular system, like human blood vessels, that transports water, minerals, sugar, growth-regulating hormones and nutrients throughout the plant, supporting its life. Like our vascular system, fluids move in two directions through different sets of tubes and pipes. These tubes and pipes are bundled together just under the skin (dermal tissue) of the roots and stems.
Working upward from the earth, tiny root hairs absorb water and minerals from the growing medium. This fluid moves through the vascular system into larger roots, the crown, into the main stem, the branches and out into the leaves. When roots are pruned, new feeder roots grow from the remaining parent.
Above ground, the leaves of plants are chemical factories. With the help of sunlight, plants feed themselves and the world by means of photosynthesis. Leaves contain the green pigment chlorophyll, which produces sugar in the presence of light, carbon dioxide, water and dissolved minerals. The chemicals travel through another set of vascular tubes and are carried to every living tissue throughout the plant to enable growth and reproduction. We harvest herb leaves for desirable flavors and beneficial chemicals. When harvesting your herbs, follow the “take a third” rule and leave the rest for the plant.
Plant stems grow either from the root straight up from a crown, along the ground or below the surface of the growing medium. They support the leaves and hold them up to the light. Stems can produce roots and reproduce new plants. Leaves, twigs, knots or buds along the stem are nodes. The vascular system, just under the dermis, stretches from node to node. Stem skin is made of waxy material or dead cork cells that protect the living wood and vascular system from heat, fire, cold, insects and disease. Use sharp tools and make clean cuts in the right places to avoid tearing the dermal tissue.
To prune properly, cut above a node. A node is the place where leaves or stems occur, which can be seen as a line, knot, bud, or collar and crotch. Potential for new growth takes place at the node, as does the fastest healing of the pruning wound. Cuts made between nodes leave a nub that has to die back to a node as it heals. This is unattractive and can allow disease to enter the vascular system of the plant.
When we cut a branch just above the collar that joins it to its parent branch, we are redirecting energy in the form of water, nutrients and hormones to the remaining branch. When we cut stem tips above a node, we are redirecting this energy to the nodes below the cut.
Leaves, stems and roots that lack a healthy color are no longer functioning as a part of the feeding system. These parts should be removed.
Prune roots when transplanting
Plants kept in pots that are too small to support the nutrient and water requirements become root-bound. To check for this, gently turn the plant out of its pot. New roots should be white, in most cases. The small roots should have hairs, which absorb water and nutrients. Captive roots displace the growing medium in search of food and water, and they twist to conform to the pot. Eventually the roots can girdle the plant and suicide ensues. Herbs in containers appreciate transplanting as needed when they are young.
Mature plants need annual root pruning for optimum health and growth. When pruning roots, use a sharp, clean knife or a pruner. Take care to maintain the integrity of the root ball by pruning away only the outer surface of the ball. Cut away dead, diseased or winding roots. Pot the root ball back into the original container with fresh growing medium, or move it into a larger pot.
It is handy to use containers as halfway houses for bare-root plants or plants you want to transplant from one place to another in the garden. First, prune the roots, pot the plant and set it in a protective place for extra nurturing to encourage new feeder roots to develop into a contained root ball. After two or three weeks in the pot, the plant will make a much easier transition to its new home.
Prune for health
Herbs need good air circulation and sunlight to dry moisture from the leaves and soil surface. Fungal organisms thrive on damp, dead tissue. Prune away some branches that are growing along the surface of the ground, as in the lateral branches of lavender and sage. Pruned in a balanced manner, the plant will retain a natural appearance while allowing air to pass around the remaining branches. Proper pruning techniques help reduce disease. Prune away diseased plant parts. Disinfect pruning shears with alcohol between each cut. Prune right above the node or crotch of a branch or twig. Sharp pruners will completely sever the branch without tearing away sections of protective bark. This will insure speedy healing of the cut.
Sharpening bypass pruners
We find our pruners to be an essential garden tool, and we favor bypass pruners, which are sharpened only on the outer edge, to the anvil type, which is sharpened on both sides of the blade. Bypass pruners give a close, even cut as the blade slides past a hook with a sharp edge. If the pruners are sharp, this results in a clean cut that does not crush stems. Anvil pruners have a sharp blade that is sharpened on both edges that meet a flat surface. This action often leaves a bit of a stub. Pruners come in all sizes and many different shapes designed to suit the various needs of the gardener. Try them out for size by holding them in your hand, or borrow a friend’s and see how they work for you. Look for blades made of tempered carbon steel so that they can be sharpened easily.
Three sharpening essentials
Although there are many sharpening gadgets on the market these days, we prefer a round-edge water slipstone, also called a Japanese slipstone or a tapered whetstone, to sharpen our pruners. These slipstones are shaped to get both flat and curved surfaces all the way down to the edge. These stones are a handy size, as they fit comfortably in the hand, a pocket and other small places. Usually of a medium fine grit, these stones are inexpensive and last virtually forever. They are versatile and can be used to sharpen many kinds of blades, from pocketknives to scissors.
Alcohol is used throughout the sharpening process. This solvent cuts through plant sap and grime and kills microbes on the pruner blades. Unlike water, it evaporates quickly, reducing the formation of rust. Unlike oil, it will not leave a residue on plant material. Alcohol dries clean. It also washes away metal filings from the pores of the sharpening stone. The grit of the stone is what sharpens the metal blades. If the grit is clogged with grime and metal filings, the stone itself becomes dull. Therefore, always wash the stone before and after the sharpening process. You’ll need a sturdy and absorbent clean cloth, which will readily soak up alcohol and can be used to wipe the blade.
When sharpening your bypass pruners, it is good to remember that the cutting edge is the one that does the actual cutting by severing the tissues, while the blunt edge holds the plant material but does not actually cut. One of the most common mistakes is to think of the cutting blade as a double-edged tool. Do not turn it over and sharpen the other edge; maintain the factory-made edges only.
Prune away pests
Aphids and mealy bugs often congregate on the young, tender tips of plants. Pruning these tips removes the pests and stimulates growth from the nodes below the point of the cut. This produces a bushier plant.
Regenerate mature perennial herbs
A combination of top and root pruning will stimulate new growth and keep plants happy in the spot they are planted. If you are consistent with annual pruning over the years, the plants should remain bushy and healthy for a very long time. These herbs grow the way they do because they spread in search of nutrients and water by rooting along lower branches. As the original plant exhausts the soil resources in its root zone, younger branches take root and become established.
Thyme, sage, rosemary, lavender and winter savory can take on a “poodle cut” appearance as they grow older. “Poodling” is a term our gardening friend, Deborah Redden, uses for this look, which we find perfectly describes new bushy growth on the end of old, bare, woody stems. The wood in the center of the plants weakens because the load is out on the ends. To avoid this problem, it is important to prune the plants at least twice in a growing season, in the spring and mid-summer. First and always, prune away dead and diseased parts. Then, prune to improve air and light circulation. Finally, take up to a third of the youngest growth at the top of the stems. The goal is to encourage new growth from lower sections of the branches and the crown of the plant.
To prune the roots of a mature plant, sink a sharp spade in a circle around the root ball. Do not tilt the spade. Just sink it straight down and bring it straight out again. This will sever roots without disturbing the root ball. New feeder roots will grow from the pruned root ball. Follow up with a drenching of liquid fertilizer, concentrating the solution into the root zone. We use liquid or granular kelp, fish emulsion — often a combination of the two for a more balanced fertilizer — or compost or manure nutrient teas to feed our herbs.
Enlightened pruning practices, as well as a better understanding of plant physiology, will give you the confidence and awareness you need to prune your herbs for bountiful harvest, health and vitality.
Susan Belsinger is long-time contributor to The Herb Companion, but this is the first time she and her herbal cohort Tina Marie Wilcox have published together here. Susan writes, cooks and gardens from her home garden in Maryland, and Tina Marie enjoys gardening in the Heritage Herb Garden at the Ozark Folk Center in Arkansas. The two currently are contributing to an upcoming book by the Brooklyn Botanic Garden on theme herb gardens.
Pick a pruner-any pruner
Now that you have the lowdown on pruning, you may wonder how to choose from the many pruners available in your local home and garden store. Pruners come in all shapes and sizes, varying in cutting power, durability, appearance, comfort, cost and more. Since personal preferences also vary, pruners mean different things to different people. Taking these factors into account, we sampled some pruners, weighing their strengths and weaknesses. Perhaps you’ll find some here that work great for you, or maybe our comments will help you evaluate pruners before you buy. If you already have a favorite set of pruners not listed here, let us know so we can share with other readers. Send your suggestions to: firstname.lastname@example.org or write to “In Basket,” The Herb Companion, 1503 SW 42nd St., Topeka, KS 66609.
* Ratings are from 1 (very poor) to 5 (excellent)
Fiskars Power-Lever® Bypass Pruner (Model 9634)
Fiskars Garden Tools
780 Carolina St.
Sauk City, WI 53583
With a surprising power-to-size ratio, this pruner proves effective for small cuts. The hinge makes for easy pruning, while the small, pocket-size design makes for easy carrying.
Retail Price: $20
Power: This mighty pruner multiplies cutting power 35 percent by combining more power with less effort and less hand stress. Its sleek design enables precision cutting in dense growth. Cuts up to 3/4-inch diameter branches.
Durability: The steel blades are fully hardened to withstand years of cutting duties.
Comfort: Although comfortable for small to medium hands, this pruner may squeeze or pinch larger fingers. The lever is built into composite handles, so when the handles are squeezed together, the bottom handle remains parallel to the top handle, minimizing friction, strain and fatigue. The lock operates with a simple touch, protecting blades and preventing accidents.
Fiskars PowerGear® Bypass Pruner (Model 7936)
For cutting through the big stuff, this is the pruner for you. This easy-to-use pruner snaps right through large roots and stems. We especially like how the handle rotates when you squeeze, which not only feels comfortable, but doubles your pruning power.
Retail Price: $30
Power: This extremely tough pruner can cut up to 3/4-inch diameter branches and provides more power with less hand stress. The bypass design is great for cutting green and growing wood. The parallel handle opening allows you to use all of your fingers when the handles are squeezed, providing for optimal hand strength.
Durability: Precision-ground steel blades are fully hardened to stand years of cutting duties, and the Xylan blade coating reduces friction and rust.
Comfort: As with the other Fiskars, the gear on this pruner is built into composite handles, so when you squeeze the handles together, the bottom handle remains parallel to the top handle, which minimizes friction, strain and fatigue. Best of all, the Fiskars 7936 has an adjustable handle opening to alter the “throw” of the opening, making it smaller for small hands or larger for big hands.
Florian Ratchet-Cut® Pruner (Model 701)
157 Water St.
Southington, CT 06489
Although they were somewhat effective, we found that these pruners didn’t work as well as either of the Fiskars or the Gardena. In one instance, it took two cuts to get through a small thistle stem. We like the sharp point on the blade, and the straight edge is good for some cuts. The ratchet comes loose easily, which creates an annoying clickety sound, and overall this pruner appears to be cheaply constructed.
Retail Price: $31 ($36.95 with holster)
Power: This patented Ratchet-Cut mechanism is supposed to multiply your strength by 700 percent, but we didn’t find it that strong. Cuts up to 3/4-inch diameter branches and is ideal for precision cutting of flowers.
Durability: This pruner seems to be cheaply made, but if taken care of, it should last long enough. The handles are fiberglass-reinforced nylon, and the high carbon steel blades are Teflon coated to resist residue buildup.
Comfort: This pruner was the lightest of the bunch, which can be handy for lugging around. The shape and size of the handles feel comfortable in most hands.
Gardena Adjustable-Grip Bypass Pruner (Model 609)
3085 Shawnee Dr.
P.O. Box 2840
Winchester, VA 22604
Accommodating to various hand sizes, this pruner makes for easy cutting no matter what your size and strength. Although effective, some people may find the safety lock difficult to use.
Retail Price: $25
Power: Best for cutting flowers, shoots and live branches, this pruner cuts up to 7/8-inch in diameter.
Durability: The aluminum construction includes a hardened steel blade that stays sharper longer and has a rust resistant coating for cleaner cuts. The rustproof spring works well but could cause problems later on if you don’t take care of it.
Comfort: The handles adjust to any hand size for maximum comfort, and the integrated rubber buffer is gentle on your wrists.
Triman Bypass Pruner (Model 2015)
Triman International, Inc.
140 Kipp Ave., Bldg. #20H
Elmwood Park, NJ 07407
As the most affordable pruner we reviewed, we felt the Triman was quite comfortable and powerful, yet not as durable as the rest.
Retail Price: $5 to $8
Power: The high carbon steel polished blades make this a tough pruner for its size, but the coil rebound tends to restrict full movement.
Durability: If not taken proper care of, dust or dirt may weaken this pruner quickly.
Comfort: The aluminum alloy handle with PVC coated grip makes for a nice, comfortable grip, which conforms well to your hand.
Do you have a favorite tool you’d like us to test? Send your ideas to: email@example.com or write “Product Tests,” The Herb Companion, 1503 SW 42nd St., Topeka, KS 66609.