Ornamental · Geraniaceae
Rozanne Cranesbill
Geranium 'Rozanne'
One of the longest-blooming perennials you can grow, and it keeps the color coming for next to no effort.
Full sun
Every 5–10 days
USDA 5–8
12–18 in · 30–46 cm
Overview
Few border plants deliver like hardy geranium 'Rozanne'. It sits squarely in the true cranesbill camp, named for the slim beak-shaped seed pods that trail the flowers, and it stands apart from the tender scented Pelargonium that borrows the everyday name geranium. Best of all, it is a cold-hardy perennial that charges back year after year across zones 5 to 8.
The bloom is the headline, and what a bloom it is. From late spring straight through to fall it keeps launching violet-blue flowers with pale white centers, often without a break, across a low spreading mound that races through a planting and blankets bare ground. That relentless show is what carried it to Perennial Plant of the Year in 2008.
It brings muscle to match the flowers, shrugging off heat better than most cranesbills and getting passed over by deer and rabbits. Hand it sun, soil that drains, and one midseason chop, and 'Rozanne' rewards you with months of color for barely any work and gets more rewarding every season.
Care
The short version: drop it into full sun to part shade in average, well-drained soil, water it through dry spells, and shear it back hard after the first flush to keep flowers firing into fall.
Light
'Rozanne' cranks out the most flowers in full sun, and it takes partial shade and partial sun in stride when you need it to. In hot regions, hand it a little afternoon shade to knock back the heat stress that makes the plant flag come midsummer.
Water
Keep it at average, medium moisture and let the top inch or so of soil dry between drinks, which lands around every 5 to 10 days. Once established it takes some drought, but never let it bake dry, and water through dry spells to keep the flowers rolling.
Soil
It grows in loam, clay, or sand and does not fuss, as long as the ground drains well. Push for moist, organic-rich soil to get its best, so work in some compost wherever you can. Forget pH, because it has no particular need.
Temperature
This tough perennial powers through winters down to -20°F (-29°C) and summer heat up to about 90°F (32°C). That range is exactly what lets it thrive across zones 5 to 8 with no special protection.
Humidity
Everyday outdoor humidity suits it, so there is no number to chase. Airflow does the heavy lifting here, since still, damp air around crowded foliage is what invites leaf spot and rust.
Feeding
It feeds light. Work compost or organic matter into the soil as the growing season kicks off, or hit it with a balanced general-purpose feed in spring, and that carries it through. Skip the all-summer feeding, because it simply does not need it.
Pruning
This is the job that really pays off. Once the first flush fades, cut the whole plant back hard to tidy it and spark a fresh late-summer or early-fall rebloom. Snip any wandering side stems whenever to keep the spread in check.
Repotting
In-ground plants rarely need lifting and divide on their own schedule. In a container, repot the moment you spot roots circling the pot, flowering easing off, or the soil drying out unusually fast.
Size & spacing
Expect a low mound around 12 to 18 inches (30 to 46 cm) tall that spreads 12 to 24 inches (30 to 61 cm) wide. Space plants toward the wider end of that range so air moves freely and the foliage stays clean.
When to plant
No frost countdown to sweat here, because 'Rozanne' is a hardy perennial and the whole aim is getting it rooted and thriving. Plant it out in spring once the last frost clears, or in early fall while the soil still holds warmth, and watch the flowers roll from late spring right through to early autumn.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Spring after the last frost, or early fall
- Harvest: Late spring (May) through summer to early fall, often nearly continuous
Hardiness
USDA hardiness zones: 5–8
Temperature: down to -29°C
Troubleshooting
'Rozanne' is famously trouble-free, so it rarely throws you a curveball, and what little shows up lands on the leaves in wet, crowded spots. Get the handful of signs below down and you can pounce early, while the fix stays quick and easy. Keep air moving and water at the base, and you head off nearly all of it.
The whole plant crashing down even with moist soil
Here is the one to take seriously: when a clump flops in the heat while the soil is still wet, southern bacterial wilt is the likely culprit, and it thrives in warm, soggy ground with no cure to fall back on. Pull the plant, destroy it, and keep susceptible perennials out of that spot for a while. Stay ahead of it in hot regions by handing the plant some afternoon shade and soil that drains fast, and it steers clear of the danger zone.
Fix:
- Remove and destroy affected plants
- Avoid replanting susceptible species in the same soil
- Reduce afternoon heat stress by providing some afternoon shade in hot climates
Brown or tan spots popping up on the leaves
Spot a few marks on the foliage and you have caught fungal leaf spot early, which is exactly where you want to be. It rides in on wet weather or overhead watering that keeps the leaves damp, so pluck off the marked ones, thin the clump to get air moving, and aim your water at the soil from here on. It never sets the plant back for long, and 'Rozanne' powers right through once things dry out.
Fix:
- Remove and discard affected leaves
- Improve air circulation by thinning or spacing plants
- Water at the base rather than overhead
Bright orange bumps studding the undersides of the leaves
Flip a leaf, catch those raised orange bumps, and you have spotted rust fungus doing its thing, which really takes off in crowded, damp foliage. Snap off the infected leaves and toss them, open the planting up to get air whipping through, and keep the water off the leaves. It stays skin-deep, so the clump keeps pumping out flowers the whole time.
Fix:
- Remove and destroy infected foliage
- Increase spacing and air circulation
- Avoid overhead irrigation
Toxicity
Great news for pet owners: true hardy geranium is safe. The cranesbills carry no toxin dangerous to cats, dogs, horses, or other animals, and they hold no poison rating for people either. The one plant to keep on your radar is the unrelated scented Pelargonium, which sometimes gets sold under the same common name.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
Cats can prowl the border all they like, because true hardy geranium is safe for cats. A nibbled leaf or flower will not poison them, and only a really big mouthful of any plant might stir up a passing stomach upset.
Dogs None
Dogs get the green light around cranesbill too. It packs no toxin, so a chewed stem or bloom brings nothing worse than the mild tummy grumble any greenery can kick off.
Horses None
Horses can graze right up to it with zero worry, since the plant holds no compounds that would harm them. Grazers usually breeze past the aromatic foliage anyway.
Rabbits None
Rabbits stay perfectly safe around it, and better yet, it lands on the list of plants they tend to skip. Plant it with confidence anywhere they roam.
Livestock None
Cattle, goats, and sheep are completely in the clear with true geranium, which carries nothing that troubles farm animals. A grazed clump costs you a plant, not their health.
Birds None
Garden and pet birds are safe around it as well. No toxin sits in the leaves or flowers, so a peck or two does no harm.
People None
People, kids included, face no poison rating from true cranesbill. Give your hands a rinse after handling any plant as a good habit, but nothing here poses a specific hazard.
Wash hands after handling as a general gardening practice; no specific toxicity hazard is reported for true Geranium.
Varieties
'Rozanne' takes top billing, but a couple of close relatives are worth grabbing if you want a lighter shade or a different flower color.
Geranium 'Rozanne' (syn. 'Gerwat')
This is the patented sterile hybrid at the heart of the buzz, a clump-former that fires off violet-blue, white-centered flowers from late spring to fall and laughs off summer heat, which is exactly why it grabbed Perennial Plant of the Year in 2008.
Geranium 'Azure Rush'
Chase a lighter look and this sport of 'Rozanne' delivers, matching the long bloom in paler, lighter blue on a neater, more compact mound.
Geranium sanguineum (Bloody Cranesbill)
A true cranesbill species instead of a hybrid, grown for its punchy magenta-pink flowers and often planted right next to 'Rozanne' to spark a fun comparison.
Companions
'Rozanne' shines as a long-blooming groundcover at the feet of taller plants, weaving between shrubs and upright perennials that enjoy the same sun and average moisture.
Plant near
Roses: Mounding hardy geranium foliage covers bare lower rose stems and provides a long-blooming groundcover at the base.
Ornamental grasses: Contrasting upright form pairs well with the sprawling mound and extends seasonal interest in borders.
Daylilies and other clumping perennials: Similar culture (full sun to part shade, average moisture) and complementary bloom times in mixed borders.
How to propagate
Since 'Rozanne' is a sterile hybrid, seed is a dead end, so forget the packets. Every new plant springs from dividing an existing clump or rooting a cutting, and both copy the parent exactly.
DivisionEasy
Spring or early fall · One growing season
Division is the fastest, surest way to turn one 'Rozanne' into many, and it clones the parent perfectly. Dig up a mature clump in spring or early fall, split it into chunks that each grab some healthy roots, and get them straight back in the ground. Each division digs in and fills out across a single growing season, so the payoff comes quick.
Stem cuttingsModerate
Spring to early summer · Several weeks to a few months to root and establish
Fancy a challenge? Root basal or softwood cuttings taken from spring through early summer, and just bring a little extra patience compared with dividing. Give them several weeks to a few months to root and take hold. Seed is simply off the menu, since the plant is sterile.
Myths
Hardy geranium 'Rozanne' is toxic to cats and dogs.
Chase this scare down and it collapses into a name mix-up. The 'Geranium' on the ASPCA toxic list is really Pelargonium, the tender scented bedding plant, which sits in a whole separate genus. True hardy Geranium, the cranesbill, including 'Rozanne', is not listed as toxic to pets, so go ahead and grow it around your animals.
You can grow more 'Rozanne' from its own seeds.
Skip the seed dreams on this one. 'Rozanne' is a sterile hybrid that sets little or no viable seed, and whatever drops will not come true to the parent. Propagate it vegetatively for guaranteed results, either by splitting a clump or rooting basal cuttings.