Rosemary care in pots, on a balcony or a sunny windowsill

Rosemary wants full sun, gritty soil and less water than you think. Overwatering is what usually kills it. This page covers where it grows well indoors and out, how to tell when it needs a drink, how to harvest it without stripping it bare, and whether it is safe around cats and dogs.

Full sun, six hours of direct light a day or more. A dim wall will not do.
Water only once the top of the soil is dry. Wet roots kill it.
Non-toxic to cats and dogs, and every sprig you cut is edible.

Does rosemary need full sun?

Yes. NC State Extension defines full sun as six or more hours of direct sunlight a day and says the plant tolerates partial shade, which on a balcony means a wall the sun reaches for half the day. Penn State Extension places its native range in dry, rocky ground around the Mediterranean, Africa, Europe and western Asia.

Short of that light, the new growth shows it first. Shoots come in long and soft with wider gaps between the needles, the colour pales, and the lower needles drop. More water or more feed does not make up for it, because the only fix is more light.

If the brightest wall you have gets no direct sun, rosemary is the wrong plant for it, and low light houseplants covers what lives there instead.

How often to water rosemary in a pot

When the top of the soil is dry, never on a fixed day. Push a finger in to the first knuckle and water only if it comes out dry. NC State names overwatering as the common cause of decline or death, so when in doubt, wait.

Light sets how fast the soil dries. In summer sun on a balcony it dries quickly, and beside a window in December it stays damp far longer. The RHS says rosemary in a container needs some water during dry spells, as long as the compost never becomes waterlogged. Soil that never dries out also breeds fungus gnats.

Brown needle tips are the signal people misread. Penn State Extension lists browning tips as a sign of root rot, so a browning plant sitting in damp soil needs less water, not more. Feel the soil before you reach for the can.

The best soil for rosemary in pots

A gritty mix that water runs straight through. The RHS asks for a peat-free soil-based compost with horticultural grit mixed in, up to a quarter of the volume, and Penn State Extension says rosemary does poorly in wet or poorly drained clay.

Water that leaves the root zone quickly gives rot less time to start. That is why a rich, moisture-holding houseplant compost is the wrong choice for this plant, however good it is for the others on your shelf.

The mix. Peat-free soil-based compost with up to a quarter grit by volume, which is the RHS recipe for containers.
The pot. Plenty of drainage holes, says the RHS. Penn State adds that clay pots dry faster, which suits this plant.
The top layer. Penn State prefers pea gravel or a sandy mulch to an organic one, because organic mulch holds moisture.

Can rosemary grow indoors all year?

It can, and it is harder than outdoors. NC State says the plant can be difficult to overwinter indoors, and Penn State Extension puts that down to low light and to too little or too much water. Indoors it needs a south-facing window in full sun or supplemental lighting, with good air circulation.

A cool room suits it better than a warm one. Illinois Extension says that indoors rosemary prefers a cool, even cold, sunny spot with high humidity. A bright unheated room does more for it than a warm living room with the same window.

Indoors is also where the pests come. Penn State lists thrips, aphids, whiteflies, mealybugs and spider mites as indoor problems, and notes that outdoor plants in full sun resist them. White cotton where the needles meet the stem is mealybugs.

Rosemary on a balcony or terrace through the winter

Outdoors is where the plant grows best. The RHS rates rosemary hardy through much of the UK, with established plants surviving temperatures as low as -8°C, and adds that harsh frosts can still damage the shoots or kill young plants.

Pots are the weak point. The RHS says plants in containers are particularly vulnerable to winter cold and that cold, wet compost can rot the roots, so in a wet spell it moves pots to a sheltered spot. On a balcony that means a wall under an overhang, out of the rain, rather than the open rail.

Choose the wall by its sun first and its shelter second. A south or west-facing wall under a roof or the balcony above gives the hours of direct light the plant needs and keeps the winter rain off its soil.

How to harvest and prune rosemary

Cut what you need when you need it, and the same cuts keep the plant compact. The RHS says rosemary is evergreen and can be harvested all year, and that the soft new growth of late spring and summer has the best flavour. NC State lists the leaves for vinegar, bread, butter, stews and meat.

Pruning is the same cut made once a year. The RHS trims it lightly every year after the flowers fade, and Penn State harvests the leaves for drying before the plant blossoms.

Choose a shoot with soft green growth at the tip.
Cut it just above a pair of leaves, inside the green part of the stem.
Take shoots from all around the plant rather than one side, so it keeps its shape.
Strip the needles by running two fingers down the stem against the way they grow.

Is rosemary safe for cats and dogs?

Yes. The ASPCA lists rosemary as non-toxic to dogs, cats and horses, under its old name Rosmarinus officinalis, and NC State marks it non-toxic for all three as well.

Keep pesticide off it, since it is a plant you eat and a pet brushes past. The RHS says control of rosemary beetle is not usually necessary, and picking the beetles off by hand keeps their numbers down. For other plants a cat can share a room with, the plant care guide marks the pet safety of each one.

Rosemary on the wall

Rosemary goes into the pocket young and stays there as long as you keep cutting it. The RHS asks for a pot at least 30 cm wide and deep for a plant growing on. The Medium pocket holds 1.8 litres of substrate behind a face of 18.5 × 20 cm, 6 cm deep, so it suits a young plant or a rooted cutting that you harvest often. Once the plant goes woody, move it to a pot of the RHS size.

The wall needs the sun before anything else. Indoors that is the wall beside your brightest window. Outdoors it is a sheltered balcony or terrace, because the recycled PVC pocket is made for weather and only the wooden board has to stay out of standing rain and out of sun from morning to night. Before you drill, design your canvas to see how the board and its pockets fit the space.

The board hangs by a slot near its top on one wall hook, so the wall side is one hole, made with a drill or, on a wall that takes one, a nail. Treat the filled weight like a heavy framed picture rather than a poster. Plasterboard takes an expanding plug, brick a standard one, and a tiled wall needs a tile bit first. The how-to guide has the seven steps.

Take a young rosemary or a rooted cutting out of its pot.
Mix grit through the substrate first, up to a quarter of the volume.
Sit the plant in, fill around it with the gritty mix and press lightly.
Water slowly, in measured amounts, and let the top dry before the next time.

Why rosemary turns brown, and other problems

Most rosemary problems start with water at the root or damp, still air around the needles, and both show first as browning. Indoors the pests join in, and fine pale speckling with webbing under the needles is spider mites.

Outdoors, the pest worth knowing is the rosemary beetle, which the RHS describes as 6 to 7 mm long with metallic purple and green stripes. Indoors, a cloud of tiny white insects lifting off when you brush the plant is a different pest altogether, and the page on whiteflies covers it.

What you see	Why	The fix
Brown needle tips, soil still damp	Root rot, from soil that stays wet	Stop watering, check the roots and repot into a gritty mix if they are soft.
Long pale shoots, needles dropping	Too little light, usually indoors in winter	Move it to the brightest window or add a grow light.
White powdery film on the needles	Powdery mildew, from humid air that does not move	Give it space and moving air, and keep water off the foliage.
Grey fuzzy mould on the stems	Botrytis, in damp and still conditions	Cut the affected stems out and let the soil dry.
Needles chewed to short grey-brown stumps	Rosemary beetle and its grey striped larvae	Pick the beetles and larvae off by hand.
Dry brittle needles, soil shrunk from the edge	Too little water, mostly in summer sun	Water slowly in small amounts until the soil takes it up again.

How to propagate rosemary from cuttings

From stem cuttings. NC State says the seeds are slow to germinate, and Illinois Extension calls cuttings the best method. The RHS takes softwood cuttings from new growth in late spring or summer, semi-ripe ones in summer, and layers low stems into the soil in spring or autumn.

In late spring or summer, cut a 15 cm tip of soft new growth.
Strip the needles from the lower half of the stem.
Push the bare stem into a pot of gritty, free-draining mix.
Keep the mix barely damp and the pot in good light.
Check for roots after 10 to 20 days, the time Penn State gives, with a gentle tug.
Pot it on, or plant it straight into the pocket, once it has rooted.

A rooted cutting is also the plant that replaces the one in the pocket once that one turns woody. Start one each summer and the next plant is always ready. Whiteflies hitch a ride on cuttings, so take them from a clean plant, and the whiteflies page shows what to look for.

Is rosemary now called Salvia rosmarinus?

Yes. Botanists moved it into the sage genus, Salvia, and Penn State Extension notes that it was previously known as Rosmarinus officinalis. It is the same plant, and many shops and older books still use the old name.

How big does a rosemary plant get?

NC State gives 4 to 5 feet tall and 3 to 4 feet wide, about 1.2 to 1.5 metres by 0.9 to 1.2. That is an unpruned plant in the ground. Regular harvesting holds a potted one at a fraction of that size.

Should you mist rosemary?

No. NC State links powdery mildew on rosemary to poor air circulation and high humidity, and wet foliage in still air is how it starts. If the air indoors is very dry in winter, stand the pot on a saucer of pebbles and water instead, which Illinois Extension suggests.

Can you cut rosemary back hard?

Yes, as long as you stay in the leafy growth. NC State says a severe prune after flowering encourages dense growth, and the RHS advises against cutting back into old wood. Both hold if you cut hard but stop where the leaves still are.