Rosemary is a great addition to any herb garden, however, it does require annual pruning to keep it looking at its best.
The main reason for an annual prune is to help slow down the formation of wood and extend the vigour and lifetime of your rosemary.
The best time of year to prune rosemary is just before growth starts in mid-spring after any risk of frost has passed.
Pruning at this time of year should avoid any frost damage to new growth, and any pruning scars that occur will be covered by new foliage in the growing season ahead.
Rosemary can be pruned from mid-spring right up until four to six weeks before the first frost in the autumn.
If rosemary is pruned after this time, it can cause the shrub to focus on growing new, tender growth rather than hardening off and protecting the growth that it already has.
If a rosemary bush does not harden itself off, it will be more susceptible to winter damage which can kill it.
One advantage of an early autumn prune is that it will encourage good air circulation, which guards against your rosemary rotting.
Rosemary blooms in late spring to early summer, and if you lightly prune after its first flourish of flowers it will more than likely bloom again in late summer.
How To Prune Rosemary
Before embarking on a rosemary pruning session make sure your secateurs are nice and clean, and sharp. Ragged cuts caused by blunt and dirty blades could leave your shrub open to infectious diseases or pests.
The shaper your blades, the cleaner the cut you will achieve, rewarding you with branches that grow back stronger.
A Light Prune Or Trim Of Your Rosemary
If you wish to give your shrub a light or a hard prune the first port of call should be to remove branches that have crossed and those that are dead and diseased.
Cut stems that have been frost damaged back to the first set of healthy leaves. Do the same for low-lying branches that show signs of fungal infection, such as drooping or discoloured foliage.
If the entire branch appears to be affected, it’s usually best to get rid of the whole thing to keep the condition from spreading.
To produce a nice bushy foliage, lightly trim your plant by cutting back two to three inches from the outer most stems. This should encourage the stems split in two, producing a nice bushy shrub.
Avoid cutting below the lower leaves and into older wood, as removing too much foliage can harm your rosemary, causing it to grow only woody stems.
Shaping Your Rosemary
Shaping your plant is one of the main reasons for trimming your rosemary. You may wish to shape it as a topiary or a hedge.
You can shape your shrub as desired, keeping the depth and angle of each cut consistent will give your rosemary, a neat and well-manicured appearance.
Try to avoid making it too uniform though, as rosemary is naturally bushy, so it’s ok for it to be a little thicker in some places.
You may wish to focus on one part of the shrub for a practical prune. For instance, your rosemary may be overtaking a nearby plant or overhanging on to a pathway, cutting back those sections will help open things up creating space.
Hard Pruning Your Rosemary
Before you give your rosemary a hard pruning, it is best to evaluate whether to cut it back or if it has become too woody, replace it with a new edition.
If your rosemary has become overgrown and needs rejuvenating start by lopping off any stems that are dead, diseased or are no longer producing foliage.
Overgrown shrubs can be cut back a third of their total size. Cutting back your rosemary by more than this could kill it off by leaving only non-productive foliage.
If you want to reduce the size of the plant further, wait six to eight weeks before cutting back the rosemary again by another third.
If you wish to keep your plant the same height, you can also cut every third stem to thin it out without affecting the overall dimensions of the shrub.
The practice of cutting out a significant amount of foliage from woody shrub is known as “rejuvenation pruning,” and can be useful for saving shrubs or trees that are failing due to exposure to harsh weather or disease.
How To Harvest Your Rosemary
If you wish to harvest your rosemary for some sprigs for your Sunday roast, the best time to do this is just before it flowers, as this is when the flavour of the rosemary will be at its peak. If you also plan to dry some rosemary this is also the best time to so.
When trimming look for stems that are at 8 inches (20cm) in length, and do not take cuttings from newly grown stems.
Cut sprigs off that are around two inches long, making sure you don’t cut too close and always leave some foliage on the stems.
To ensure you always have enough mature stems to clip, it is a good idea to keep more than one plant in the garden. Two or three should be more than adequate for most households.
Never harvest more than a 1/4 of your rosemary bush at a time. Leaving at least 3/4 of your plant will ensure that it continues to thrive and produce new sprigs.
When drying your cuttings, tie them together in evenly sized sprigs and hang them in a dark, dry and well-ventilated part of your house.
After around ten days your rosemary should be completely dry and ready to take down to strip off the leaves and store in a jar or an airtight container.
Also if you cut sprigs for harvest while your plant is in bloom, you can use the flowers for cooking as well, as apparently, they are edible as well.
Growing Rosemary From Cuttings
As mentioned before it is a good idea to keep more than one rosemary in your garden if you plan on using it for harvesting, but instead of purchasing more plants why not grow your own from cuttings from the plant that you already have planted in your garden.
Even if don’t use your rosemary for harvesting, you can grow free plants from the cuttings that you take from your annual prune of the shrub.
There a couple of valid reasons for growing rosemary from cuttings:
A rosemary plant raised from a cutting will mature more quickly than a plant grown from seed, and rosemary seeds tend to have a low germination rate and take a long time to grow. A rosemary cutting will reach a usable size in just a few months, and be ready to harvest much more quickly.
Same As The Donor Plant
The plant you grow from a cutting will be an exact clone of the donor plant and have the same disease resistance, growth and flavour.
How To Take Cuttings From Your Rosemary
- First, you need to select which stems to use from your donor plant. Choose healthy stems that have fresh growth, younger shoots will have green stems that are flexible. Avoid taking cuttings from woody stems.
- Using secateurs take a cutting around 5 to 6 inches back from a fresh growing tip.
- Gently strip off the lower 2 inches of leaves from the cutting.
- Place the cutting in water and place in a warm position away from direct sunlight. Change the water every couple of days with room temperature water. The fresh water will provide dissolved oxygen that prevents the cutting from rotting.
- The cutting should grow roots in a few weeks depending on the room temperature. After 6 to 8 weeks it should be apparent to see if the cutting has taken. Cuttings that have failed will be brown and will have shed leaves.
- Pot up the cutting once roots develop, using a sandy soil mix that drains well. Mix equal parts of multi-purpose potting soil and sharp sand, or use cactus-potting soil.
- Fill a 4-inch pot with slightly damp potting soil for each rosemary cutting. Use a pencil to make a 3 to 4-inch hole into the soil. Place the cutting in the hole with care to avoid damaging the roots. Cover gently and water thoroughly.
- Place the newly potted rosemary plant in indirect light or in filtered sunlight until roots become established, and then move to direct light, at least 6 to 8 hours per day. Keep the potting soil moist until you see new growth.
- Let the new plants to put on some growth before harvesting. Once the plant is 6 inches tall, harvest by cutting stems as needed. New growth will continue forming on the stem.