Take a Fifth of a Rosemary, and Never the Bare Wood

Rosemary is sold everywhere, which makes people assume it is hardy everywhere. It is not.

The species is winter hardy only to zone 8a. Named cultivars stretch that a little, with Arp rated to zone 7a and potentially 6a with protection, and Madeline Hill to 7a or 6a in a protected site, but the base plant is a warm climate shrub.

In colder regions it is a pot rather than a shrub, brought inside before the first frost and put back out in spring. That is a different plant to own and a different plant to cut.

A rosemary that browned off over a hard winter looks exactly like a rosemary that has got away from you. Both are gray, open and sparse in March, and only one of them will answer a cut.

The test takes a second and settles it. Scrape a little of the thin outer bark off a stem with a thumbnail, and look at what is underneath.

Bright green under the bark means live tissue and a plant worth working on. Dry pale brown means that stem is dead, and cutting it back does nothing for the plant except remove what was propping it up.

Every cut stays in the leafy green part of the stem.

Trace any branch inward from its tip and you reach a point where the needle leaves stop and bare gray wood begins. That line is the whole rule, and it moves outward a little further from the crown every year the plant is left alone.

Wisconsin Horticulture puts it directly, advising against cuts into the woody parts of stems unless the plant is being shaped. A cut below that line rarely produces a new shoot, and the stub simply stays a stub.

The reason is that rosemary carries very few dormant buds in old wood, so there is nothing there for a cut to release. It is not sulking, it has nothing left to grow from.

That is also why light regular cutting matters more than any single big one. A plant trimmed often keeps green growth low down on its stems, so the safe line stays close to the crown and the plant stays reducible.

Less than most people think, and less than most pages say.

Wisconsin Horticulture puts the ceiling at 20 percent of the growth at a time. The figure that circulates elsewhere is a third, and the difference is not academic on a plant that cannot regrow from what is left behind if you overshoot.

A big reshaping therefore becomes several sessions rather than one. Take a fifth, let the plant respond, and come back a few weeks later in the same growing season.

Shaping is done early rather than late. Frequent tip pinching while a plant is small builds a dense habit from the start, and does more for the final shape than any cut made years afterwards.

Dead and damaged growth sits outside the ceiling. It comes off whenever you find it, and it does not count against the 20 percent, since it was contributing nothing anyway.

On rosemary these are the same job.

Both harvesting and pruning remove soft green growth from the outside of the plant, so a cook taking sprigs through the season is running the pruning routine without calling it one.

The cut goes a few inches back from a tip, well inside the leafy part, leaving needle foliage on the piece that stays behind. That is a harvest and a tip pinch at the same time, and the plant branches at the cut.

Move around the plant while you pick. Taking every sprig from the side nearest the kitchen door leaves a lopsided bush within a season, and the bare side takes years to fill.

Frequency does the shaping. A plant picked from regularly through the growing season rarely needs a separate pruning job, and it never gets far enough away to need one.

Slowly, and only if there is enough green left to work with.

An old rosemary opens out from the middle. The thick stems splay outward, the center becomes bare gray wood, and the green retreats to the ends of the branches.

That geometry is the problem. If the only foliage is at the tips then every safe cut is at the tips too, which means the plant cannot be made much smaller no matter how much you want it to be.

What is available is a slow tightening. Take 20 percent from the outside each season, pinch whatever new growth appears to force it to branch, and the plant thickens up over several years rather than one.

Some plants are past it. A rosemary with almost no green below the branch tips has nothing to rebuild from, and no amount of patience changes that.

The replacement is free, which softens the decision. Rosemary roots readily from cuttings, so the plant being given up on can supply the plant that replaces it.

Cut while the plant is growing, and stop before the cold.

Cutting belongs in the growing season, when there is enough warmth and light for the plant to replace what came off. A cut made as the season closes leaves an opening the plant cannot answer until spring.

A potted plant comes inside before the first frost rather than after it. Waiting for damage and then rescuing the plant is how most of them are lost.

The indoor spot wants two things that rarely come together. Cool temperatures around 50 to 60 degrees Fahrenheit and very bright sunlight, which usually means an unheated room with a good window rather than the warm kitchen it came out of.

The thing that kills it indoors is not the cutting. The biggest cause of decline and death on an indoor rosemary is overwatering, and root rot and botrytis are the diseases that follow.

Dry indoor air complicates the reading, because it produces brown leaf tips and dieback that look like thirst.

Watering harder in response is how a plant that was drying out at the tips ends up drowning at the roots.

The overwatering guide covers the check that separates them.