Herb · Rutaceae
Rue
Ruta graveolens
Give rue full sun and lean, dry soil and this gentle old herb rewards you with years of tidy blue-green growth.
Full sun
Every 7–14 days
80–120 days
USDA 4–9
Overview
Rue is one of those forgiving old herbs that makes a grower feel capable. It is a tough, blue-green evergreen with deep roots in cottage gardens and apothecaries, growing as a woody perennial that reaches 2 to 3 feet (60 to 90 cm) tall. Small mustard-yellow flowers open through the summer, and while people once cooked with it, these days it is happiest earning its keep as an ornamental and a welcome home for swallowtail butterflies.
Here is the reassuring part: what makes rue easy is exactly what new growers tend to overthink. It asks only for lean, sharply drained soil and full sun, and it happily shrugs off both drought and cold down to -20°F (-29°C). Resist the urge to pamper it, because rich ground and constant watering are the one real misstep, and soggy roots do more harm than any dry spell ever will.
The single thing to take seriously is the sap. Rue carries furanocoumarins, and if the sap lands on your skin and then meets sunlight, it can bring on painful, blistering burns. None of this makes the plant hard to live with. Slip on gloves and long sleeves before you handle it, plant it away from pets and curious children, and keep it out of the kitchen, and you and your rue will get along fine.
Care
The short version: rue loves full sun, lean and sharply drained soil, and a deep drink only after the top half of its soil dries out. Cut it back hard each spring, feed it little or not at all, and keep a pair of gloves handy every time you handle it.
Light
Rue truly wants full sun, and the more it gets, the better. Bright light is what keeps its neat blue-green shape, so while it will accept a bit of afternoon shade, a shaded plant tends to stretch, flop, and thin out.
Water
Go easy here, because less really is more. Water deeply but only every 7 to 14 days, and wait until the top half of the soil has dried before the next drink. Rue handles drought well once established and hates wet feet, so constant damp is the surest path to rotted roots.
Soil
Give rue lean, sharply drained soil, sandy or loamy, the sort many herbs merely put up with. Any pH from 6.0 to 7.8 will do, and honestly, poorer ground works in your favor by keeping the growth compact and sturdy.
Temperature
This is a genuinely hardy plant, comfortable in heat up to 95°F (35°C) and cold all the way down to -20°F (-29°C). That resilience is exactly why it comes back on its own year after year across zones 4 through 9, with no fuss or winter coddling.
Humidity
Rue likes the air on the dry side, somewhere around 30% to 50%, which fits its Mediterranean background. The main thing to steer clear of is damp, stagnant air, since it encourages the very rot this plant is already inclined toward.
Feeding
Feed rue lightly in spring, or simply skip it altogether. It flourishes in poor soil, and a generous hand with fertilizer only produces weak, floppy stems that splay open and lose that tidy, rounded form.
Pruning
Cut rue back hard in early spring to clear the old woody growth and coax out fresh, compact leaves, then give it a light tidy once flowering is done. Always wear gloves and long sleeves, and choose a cloudy day, because sap on bare skin followed by sunshine can cause blistering burns.
Repotting
A rue grown in a container only needs moving up every 2 to 3 years. Repot it when roots start circling the pot or slip out the drainage holes, when water rushes straight through, or when new growth turns sparse and stunted.
Size & spacing
Rue settles into a rounded little shrub, 2 to 3 feet (60 to 90 cm) tall and 18 to 24 inches (45 to 60 cm) wide. Give each plant that full share of space so air can move around it and the leaves stay dry.
When to plant
Rue is a patient, hardy perennial, so give it time to find its feet. Start the seed indoors in the last stretch of winter, move young plants outside in spring after the last frost fades, and then simply enjoy the mustard-yellow flowers that appear all summer long, from about June into August.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Sow: 6-8 weeks before last spring frost
- Plant: spring, after danger of frost has passed
- Harvest: Mustard-yellow flowers in summer (roughly June-August); grown ornamentally - do NOT harvest the foliage for eating due to toxicity and phototoxic sap.
Hardiness
USDA hardiness zones: 4–9
Temperature: down to -34°C
Troubleshooting
Rue is genuinely forgiving once it settles in, and nearly all of its troubles trace back to a little too much water or a skipped pruning. Catch the early signs below and a simple change of habit usually sets things right, no rescue needed. Look for what matches your plant, then step in gently before the roots or the shape drift too far.
Wilting, yellowing, and a plant that keeps sinking
When rue wilts, yellows, and slowly gives way, the trouble is almost always root rot from wet feet. This plant hates sitting in soggy ground, so heavy clay or a heavy watering hand quietly rots the roots from underneath. Ease off the water right away, work some grit or sand into the bed to open up drainage, and gently lift out any plant whose roots have already turned brown and mushy.
Fix:
- Reduce watering immediately and allow soil to dry
- Improve drainage by amending with grit or sand, or relocate to a raised/well-drained site
- Remove and discard severely rotted plants
Bare woody stems with leaves clinging to the tips
A plant left unpruned and leggy lets its base go woody and drops its lower leaves, so only the tips stay green. Too little light makes it reach and stretch, which makes the look worse. Cut it back hard in early spring and rue answers with fresh, compact shoots, but do give it full sun or it will simply stretch all over again.
Fix:
- Cut back hard in early spring to encourage compact new shoots
- Ensure the plant receives full sun
Blue-green leaves nibbled bare by caterpillars
Those green-and-black banded caterpillars are swallowtail butterfly larvae, and rue happens to be one of their favorite host plants. Most growers happily leave them to it and treat the chewed leaves as a small price for a garden full of butterflies. If the damage really bothers you, lift the caterpillars off by hand and move them elsewhere, and please skip the broad sprays that would kill them outright.
Fix:
- Tolerate the caterpillars where butterflies are desired, as rue is a valued host plant
- Hand-pick and relocate caterpillars if damage is unacceptable
Toxicity
Think of rue as a plant to admire rather than touch or taste. Its sap holds furanocoumarins that can cause serious sun-triggered skin burns, and the leaves are toxic to cats, dogs, horses, and grazing animals if eaten. No part of it belongs on a plate, so wear gloves when you handle it and give it a spot well away from pets and children.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Moderate
A cat that nibbles rue or brushes against its sap will often drool, be sick, and get loose stools, then grow quiet and a little withdrawn. The same oils can leave its skin red and sore.
Dogs Moderate
After a dog chews the leaves, keep an eye out for drooling, vomiting, and diarrhea, often trailed by low energy and a patch of inflamed skin wherever the sap touched down.
Horses Moderate
Grazing on rue tends to upset a horse's stomach, and the sap can blister or inflame the skin, especially on pale, sun-exposed muzzles and lower legs.
Rabbits Toxic
It is kindest to keep rabbits well clear of rue. The furanocoumarins make the leaves unsafe to eat, and a curious rabbit can end up with a sore belly and irritated skin.
Livestock Toxic
Grazing animals that eat rue can suffer digestive upset and photosensitization, where sun-exposed skin reddens and blisters once the plant builds up in their system.
Birds Caution
Birds have little reason to bother with the bitter foliage anyway, and those same phototoxic compounds make rue a plant to keep out of their reach rather than offer.
People Caution
No part of rue is a casual snack, and the real risk is to your skin: brush the sap and then step into sun, and painful, blistering burns can follow. Wear gloves and long sleeves every time you handle or prune it.
Always handle rue with gloves and long sleeves, and avoid contact on sunny days, because sap on skin followed by sunlight causes painful blistering burns (worse than parsley or celery). The plant must NOT be eaten by people or animals and is not used as a modern culinary herb.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
Only a couple of named forms show up in gardens, and both are grown for their foliage more than any change in how you use them. These two are the ones worth getting to know.
'Jackman's Blue'
A compact selection prized for its unusually deep blue-green leaves, which keep their color right through the season.
'Variegata'
Its foliage comes splashed and edged in creamy white, lending the plant a softer, gently mottled appearance.
How to propagate
Rue takes happily to both seed and cuttings, so long as you bring a little patience and, for cuttings, a good pair of gloves.
SeedModerate
Start indoors 6-8 weeks before last frost, or sow outdoors in spring; germination can be slow · Several weeks to germinate and a full season to establish
You can start rue from seed indoors 6 to 8 weeks before your last frost, or sow it right into the spring garden. Rather than burying the seed, press it gently onto the surface, since a little light helps it wake up, and keep the soil evenly moist until the seedlings show. Do be patient, because germination comes slowly and the plant needs a full season to truly settle in.
Stem cuttingsModerate
Take softwood or semi-ripe cuttings in late spring to summer · 4-8 weeks to root
Take softwood or semi-ripe cuttings anytime from late spring through summer and root them in a gritty, well-drained mix, where they should take hold in 4 to 8 weeks. Keep your gloves on the whole time you cut and handle the stems, since the sap can burn skin out in the sun.
Myths
Rue is a safe kitchen herb you can cook with as freely as any other Mediterranean seasoning.
Old cooks did reach for it, but modern guidance no longer treats rue as food. It is toxic to eat, and its sap can trigger severe, sun-driven skin reactions, so its rightful home today is the garden as an ornamental and historical herb, never a culinary one.