Ornamental · Geraniaceae
Rozanne Cranesbill
Geranium 'Rozanne'
One of the longest-blooming perennials for a considered garden, and it holds a border together all season.
Full sun
Every 5–10 days
USDA 5–8
12–18 in · 30–46 cm
Overview
Some plants earn their place by the effect they create, and hardy geranium 'Rozanne' is one of them. A true cranesbill, named for the slim beak-shaped seed pods that follow the flowers, it is a different plant from the tender scented Pelargonium that borrows the everyday name geranium. As a cold-hardy perennial it returns across zones 5 to 8, giving a garden the kind of continuity that a considered planting relies on.
The appeal is its long, easy season. From late spring into fall it holds violet-blue flowers with white centers, nearly without pause, on a low mound that spreads through a border and softens the ground between larger plants. That steady presence, the sort that carries a scheme from one month to the next, is what won it Perennial Plant of the Year in 2008.
It settles naturally into the rhythm of a low-maintenance garden. Untroubled by heat and generally left alone by deer and rabbits, it wants little more than sun, drainage, and a midseason trim, and in return it lends a planting months of color for very little upkeep, the definition of a plant that works while you enjoy the space.
Care
The short version: place it in full sun to part shade in average, well-drained soil, water it through dry spells, and shear it back after the first flush to carry the flowers into fall.
Light
'Rozanne' gives its fullest flowering in full sun, and it settles just as well into partial shade or partial sun where a border needs it. In warmer gardens a stretch of afternoon shade suits it, easing the heat stress that can leave it flagging by midsummer.
Water
Keep it at average, medium moisture and let the top inch or so of soil dry between waterings, which lands around every 5 to 10 days. An established plant carries some drought, but it looks its best kept from going dry, so water through dry spells to hold the display.
Soil
It asks little of the ground and takes to loam, clay, or sand so long as the drainage is good. Moist, organic-rich soil brings out its best, so a little worked-in compost is worthwhile. There is no particular pH to plan around.
Temperature
This cold-hardy perennial takes winters to -20°F (-29°C) and summer heat near 90°F (32°C) in its stride. That easy range is what lets it hold a border across zones 5 to 8 without special care.
Humidity
Ordinary outdoor air suits it, so there is no level to manage. Air movement is what counts, since still, damp air around a crowded planting is what opens the door to leaf spot and rust.
Feeding
It lives on very little. Work some compost or organic matter into the soil as the season opens, or offer a balanced general-purpose feed in spring, and that sees it through. There is no call to keep feeding across summer.
Pruning
This is the one gesture that pays a garden back. After the first flush fades, cut the whole plant back hard to refresh it and prompt a fresh late-summer or early-fall rebloom. Trim any wandering side stems whenever they stray past where you want the planting to sit.
Repotting
In the ground it rarely needs lifting and divides on its own quiet schedule. In a container, repot when you notice roots circling the pot, the flowering easing, or the soil drying out unusually fast.
Size & spacing
Count on a low mound of about 12 to 18 inches (30 to 46 cm) tall spreading 12 to 24 inches (30 to 61 cm) wide. Setting plants toward the wider end of that range keeps air moving and the planting looking clean.
When to plant
'Rozanne' is a hardy perennial, so the aim is a settled plant rather than a race against frost. Set new plants out in spring once the last frost has passed, or in early fall while the soil holds its warmth, and the border reads with flowers from late spring 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 undemanding, and the little that does appear tends to surface on the leaves where a planting sits wet and crowded. Knowing the few signs below lets you step in early, while the remedy is still an easy one. Good air movement and watering at the base keep nearly all of it away.
A clump collapsing despite a well-watered border
A plant that folds in the heat while the ground stays moist points to southern bacterial wilt, a disease at home in warm, waterlogged soil that leaves no room for rescue. Lift the affected plant, dispose of it, and hold off on setting another susceptible perennial in that place. In warmer gardens, a spot with afternoon shade and soil that drains cleanly keeps the planting comfortably out of reach of it.
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 marking the leaves
A scatter of marks across the foliage usually signals fungal leaf spot, which settles in after wet weather or overhead watering leaves the plant sitting damp. Clip away the affected leaves, give the planting a little breathing room so air can pass through, and keep future watering at the base. It stays a surface blemish, and the clump looks its polished self again once the border dries out.
Fix:
- Remove and discard affected leaves
- Improve air circulation by thinning or spacing plants
- Water at the base rather than overhead
Orange flecks hiding beneath the leaves
Lift a leaf and the raised orange specks underneath are rust fungus, which travels fastest through a crowded, damp planting. Remove the affected leaves for the compost, ease the spacing so air can circulate, and keep the watering off the foliage. The trouble never reaches past the surface, so the display carries on blooming right through it.
Fix:
- Remove and destroy infected foliage
- Increase spacing and air circulation
- Avoid overhead irrigation
Toxicity
For a household with pets, the verdict is easy: true hardy geranium is safe. The cranesbills carry no toxin dangerous to cats, dogs, horses, or other animals, and no poison rating for people either. The one plant to watch for is the unrelated scented Pelargonium, sometimes sold under the same common name.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats None
A household cat can share the garden freely, since true hardy geranium is safe for cats. A nibbled leaf or bloom brings no poisoning, though a large mouthful of any plant might leave any animal briefly out of sorts.
Dogs None
Dogs move through a cranesbill planting with nothing to fear, because it holds no toxin. A chewed stem or flower amounts to nothing beyond the passing upset any greenery can bring.
Horses None
Horses can graze the surrounding ground in comfort, as the plant carries no compounds that would harm them. Grazing animals also tend to bypass the aromatic foliage on their own.
Rabbits None
Rabbits come to no harm from it, and it happens to be one of the plants they usually pass over. That makes it a graceful choice for a garden they visit.
Livestock None
Cattle, goats, and sheep are in no danger near true geranium, which holds nothing that troubles farm animals. A grazed clump is a loss to the border rather than to their health.
Birds None
Garden and pet birds alike are safe around it, since neither the leaves nor the flowers carry a toxin. A stray peck does no harm at all.
People None
For people, children included, true cranesbill carries no poison rating. A rinse of the hands after any time in the border is simply good habit, with no particular hazard tied to this plant.
Wash hands after handling as a general gardening practice; no specific toxicity hazard is reported for true Geranium.
Varieties
'Rozanne' leads the group, but two close relatives are worth knowing when a scheme calls for a lighter shade or a different flower color.
Geranium 'Rozanne' (syn. 'Gerwat')
This is the patented sterile hybrid at the center of it all, a clump-former that carries violet-blue, white-centered flowers from late spring to fall and holds its poise through summer heat, the very qualities that made it Perennial Plant of the Year in 2008.
Geranium 'Azure Rush'
For a lighter, more understated palette, this sport of 'Rozanne' offers the same long season in paler blue on a neater, more compact mound that suits smaller settings.
Geranium sanguineum (Bloody Cranesbill)
A true cranesbill species rather than a hybrid, prized for bright magenta-pink flowers and often placed beside 'Rozanne' where a bolder note is wanted in the scheme.
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
Because 'Rozanne' is a sterile hybrid, there is no growing it from seed. Every new plant comes from dividing an established clump or rooting a cutting, both of which reproduce the parent exactly, a tidy way to extend a planting you already love.
DivisionEasy
Spring or early fall · One growing season
Division is the surest way to build more of this sterile hybrid for a border that grows richer each year. Lift a settled clump in spring or early fall, part it into pieces that each hold healthy roots, and return them to the soil straight away. Every division finds its footing and fills out across a single growing season.
Stem cuttingsModerate
Spring to early summer · Several weeks to a few months to root and establish
Basal or softwood cuttings taken from spring through early summer offer a second, more patient route to new plants. Set aside several weeks to a few months for them to root and settle. Seed is never part of the picture here, since the plant is sterile.
Myths
Hardy geranium 'Rozanne' is unsafe to plant where pets roam.
The worry traces to a shared name rather than any real hazard. The 'Geranium' on the ASPCA toxic list is Pelargonium, the tender scented bedding plant from a separate genus entirely. True hardy Geranium, the cranesbill, including 'Rozanne', is not listed as toxic to pets, so it earns a place in a home garden without reservation.
You can raise new 'Rozanne' plants from collected seed.
It sounds thrifty, but 'Rozanne' is a sterile hybrid that sets little or no viable seed, and what little it drops won't return true to the parent. The dependable path to more plants is vegetative propagation, whether by dividing a clump or rooting basal cuttings.