The garden is still remarkably dormant. I’m waiting to see if there will be any signs of green on the lower branches of my butterfly bushes or if I can cut them all the way to the ground and let the new growth come in from the crown. The hydrangeas show no interest in getting an early start and I was quite dismayed to see that my carpet roses had been pruned for me by the rabbits. They left me with a good deal more dieback than I usually experience.
In the vegetable garden, my eyes are peeled on the perennial herbs: sage, thyme, oregano, salad burnet, comfrey, and lavender. The comfrey and salad burnet are sending up new growth, so they don’t count as woody herb. But the others don’t seem convinced that spring is really, truly here. They remain a listless brown, pretending to have thrown in the towel. I know I have to be patient, but patience is running thin these days.
Some spring pruning of woody herbs is necessary. During the growing season, the pinching and snipping we do when we harvest herbs for cooking is enough to keep the growing bushy and lush. But winter is not often kind to these herbs, in our area. If they make it through winter with some life left in them, they are going to need a little rejuvenation pruning.
When and How to Prune Woody Herbs
Wait until you see new growth either at the base of the plant or from the lower stems. This tells you the plant is coming out of dormancy and is ready to start growing again.
Prune them back by 1/3 to ½ of the old growth. Don’t worry, they will fill in quickly and the new growth will be much more flavorful than the old woody stems.
You can prune again, when the herbs are in bloom or shortly after. The flowers of these culinary herbs are also edible, so don’t be hesitant to snip a few for the kitchen.
For the rest of the growing season, cutting stems to use in cooking should be all the pruning the plants will require. For goodness sake, use your herbs. The more you cut them, the fuller they will become.
Sooner or later your perennial herbs are going to need replacing. No plant lives forever. When you notice the center of the plant dying out or when the stems start drying or thinning out, it’s probably best to lift that plant and start with a new one.
Here are more specific pruning tips for each plant.
Lavender plants behave as other perennial flowers, taking 3 years to really become established. Annual pruning will help them form thick plants that will be healthier and longer lived than with no pruning. Lavender let to its own devices will become woody, flowering a little less each passing year.
Two big hurdles of over-wintering lavender in USDA zones 6 and lower are the repeated freezing and thawing of winter, as well as cold damp soil. Leave your plants standing in the fall, so the top growth can act as insulation. Then give the plants time to wake up in the spring, before you do any pruning. Wait until you see signs of new growth. But don’t wait too long or you risk pruning off the forming flower buds. A good rule of thumb is to prune when the tulips are in bloom.
With all the woody herbs, it is important to never prune so low on the plant that you are cutting into tough, leafless stems. The woody part of the plant may not regrow, if pruned too drastically. Don’t let that intimidate you, just proceed with caution.
The first year, all you want to do is find where the stems chance from woody to soft and green and prune about 2 – 3 inches above that. This will encourage root growth and created a fuller plant.
By its second year, your lavender should double in size and have a lot more flowers. The time to prune is while it is in flower or as the flowers just start to fade. I know it can be tough to prune off the flowers, but getting the plants established really does pay off in the long run. Muster your courage and gather the flower stems together. Then once again, cut about 2 -3 inches above where the stems transition from woody to soft and green. Don’t cut straight across, rather follow the natural shape of the plant. You want to wind up with a neat, rounded, mound.
You’ve made it to year 3, congratulations! By now, your plant should be quite impressive. At this point, the best time to prune is when the flowers are just opening. That’s not a problem, if you are growing the plants to harvest the flowers. The buds will continue to open after they are cut. You don’t need to be so severe with your pruning now. Just trim back to the base of the flower stalks, again following the contours of the plant. I find a small sythe or garden knife works better than a hand pruner, for this job.
Oregano is a relatively tall (12 – 18 in.), but floppy plant. Although it is in the same family as mint and will spread out a foot in all directions, it is nowhere near as aggressive as mint.
It is one of the hardiest woody herbs, and makes it through tough winters a bit tattered, but unscathed. When you start to see new green growth, shear aff about ½ – 2/3s of the top growth, making sure you are not cutting into the leafless, woody stems. It may seem harsh, but the plants will start filling in right away.
Regular harvesting is the best pruning technique for oregano. Even if you don’t plan to use it fresh, you can always dry the sprigs, throughout the summer. Although, if you let it go to flower, you will be rewarded with swarms of delighted bees, which can be a blessing in a vegetable garden. Deadhead the flowers, after bloom, for another flush of green growth to harvest at the end of the season.
Rosemary is too tender to be left outdoors during winter in USDA zones 5 and lower. It can be brought indoors, but it will need lots of attention. You want to make sure it has enough water and humidity to keep it from drying out, but not so much that it gets powdery mildew. It is a balancing act, to be sure, but if you check it regularly, it can be done.
Rosemary, as with most evergreens, doesn’t really like being pruned. However it doesn’t naturally growth in a full, compact form, so most gardeners do some judicial pruning.
Wait until the plant is actively growing. Ideally, prune your plants after they bloom, in the spring. Deadheading may be all that is required. You can cut back a few inches, if you want to keep your plant small, but do not cut back into leafless, woody stems. They will not regrow.
If you need to reduce the size of your plant (lucky you) or you want to encourage a fuller plant, do it slowly. Cut only ⅓ of the stems at a time and only cut them by about ⅓ their length. You can repeat this on another ⅓ of the plant once you see new growth sprouting from the initial cuts.
Of course, you can prune by harvesting as needed. That may be all you need to do, to keep your plant looking good. And never waste the cuttings. Store them in a paper bag, to dry and use for cooking.
Sage competes with oregano for winter hardiness, although the golden and tri-colored varieties are a bit more tender than common and purple sage. But even common sage looks a bit haggard by spring. If you left your plants standing tall in the fall, they will have fallen over by spring and the lower leaves will be tattered.
Prune them by at least half, in mid-spring. If the plants are looking a bit leggy or sparse, you can prune back to 4 – 6 inches from the ground, as long as there are still shoots on the stems. Sage can root when it touches soil, so you may have fresh new plants already filling in.
You can harvest sprigs as needed. If you use your plants a lot, they may never flower. However if you do allow them to flower, give them another good pruning of about ⅓ to 1/2 , immediately after flowering, to rejuvenate the plants.
Most thyme plants require minimal care, especially if you are harvesting sprigs regularly. The first year, you won’t need to prune them at all, unless you are not going to harvest from the plants. If that’s the case, pinch the tips periodically, to spur bushy new grow.
In subsequent years, give them a rejuvenating pruning in the spring, when you start to see new, green growth. Shear the plants back by about ⅓, to where there are new shoots. Don’t prune so far down you are cutting into leafless, woody stems. A spring trimming should encourage lots of new, tender, flavorful growth.
Not all varieties are hardy in USDA Zones 5 or lower, so don’t be too disappointed if your plants don’t make it through a tough winter. Covering them with a layer of leaves or evergreen branches, after the ground freezes in the fall, will help insulate them from harsh winter winds and may improve their chances of survival. But if you have to replace your plants, take heart. New plants will grow and fill in quickly.
Okay, let’s grab our pruners and go for it!