Ashy Rock-spiraea Plant Care
Petrophytum cinerascens (Piper) Rydb.
Updated · Sources · How we source care data
Petrophytum cinerascens is a rare species of flowering plant in the rose family known by the common names halfshrub rockmat and Chelan rockmat. It is endemic to the state of Washington in the United States, where it occurs in just a few locations along the Columbia River in Chelan and Douglas Counties.
Full sun to partial shade
At a glance
How do you care for Ashy Rock-spiraea?
Plant Ashy Rock-spiraea in full sun to partial shade.
Where Is the Ashy Rock-spiraea Native To?
What Is the Ashy Rock-spiraea?
Ashy Rock-spiraea (Petrophytum cinerascens) belongs to the Rosaceae family within the Petrophytum genus. Ashy Rock-spiraea is native to the state of Washington in the United States. Ashy Rock-spiraea is also known as Rock-spiraea.
Ashy Rock-spiraea displays a low rosette, clumping growth habit, reaching up to tall with a spread of approximately . Ashy Rock-spiraea produces small white or pink flowers in dense clusters.
What Light Does the Ashy Rock-spiraea Need?
Ashy Rock-spiraea thrives in full sun to partial shade.
Light Requirement
Full sun to partial shade
What Soil Mix Works Best for a Ashy Rock-spiraea?
Well-draining sandy loam with added organic matter for moisture retention. Good drainage is essential for Ashy Rock-spiraea to prevent waterlogging, which leads to root rot and fungal issues.
Where Should You Plant a Ashy Rock-spiraea?
Choose a spot with full sun to partial shade and well-draining sandy loam with added organic matter for moisture retention. Avoid low spots where water collects after rain.
Plant container-grown or balled-and-burlapped trees in spring or early autumn, setting the root flare at soil level, and water well after planting.
How Do You Prune a Ashy Rock-spiraea?
Prune Ashy Rock-spiraea while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.
If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the tree in one year.
How Do You Care for a Ashy Rock-spiraea in Winter?
Water deeply in late autumn before the ground freezes, and spread a 5–8 cm (2–3 in) layer of mulch over the root zone, keeping it away from the trunk.
Young and container-grown trees need extra protection: roots in a pot freeze much more easily than roots in the ground.
How Do You Propagate a Ashy Rock-spiraea?
Ashy Rock-spiraea can be propagated through seeds, division of offsets. Similar propagation techniques also apply to tufted rock-spiraea plant care, which shares the same genus.
Is the Ashy Rock-spiraea Toxic to Pets and Children?
Pet safety not verified
The ASPCA does not list Ashy Rock-spiraea, so we can't confirm whether it is safe for cats and dogs. Keep pets from chewing it as a precaution.
This is a general caution, not veterinary or medical advice. If your pet ate a plant, contact your vet or animal poison control.
See all plants toxic to cats and plants toxic to dogs.
What Pests and Diseases Affect the Ashy Rock-spiraea?
Ashy Rock-spiraea is susceptible to aphids, spider mites, scale insects. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.
Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.
Keep exploring plants
Ashy Rock-spiraea is one of many species covered in the complete plant care and identification guide, which groups plants by genus, attribute, and popularity.
It belongs to the Petrophytum genus — compare its care with other Petrophytum species on PlantoScan.
Petrophytum is part of the Rosaceae plant family — browse all Rosaceae genera and species.
Ashy Rock-spiraea thrives in bright light and direct sun — see other bright-light plants.
Related Plant Care Guides
Closely related plants with similar care requirements:
Sources
- Scientific name & taxonomy: Petrophytum cinerascens (Piper) Rydb., family Rosaceae (first published in N. Amer. Fl. 22: 253 (1908)) — World Flora Online record, IPNI name record.
- Pet toxicity: Pet safety not verified: the ASPCA does not list Ashy Rock-spiraea, so we can't confirm whether it is safe for cats and dogs. Checked against the ASPCA plant list; any other toxicity note on this page comes from PlantoScan's plant database.
- Care values(watering, light, temperature, humidity, soil, fertilizing): PlantoScan's plant database, filtered by automatic plausibility checks — values that fail them are hidden. How we source and check plant data.
Spotted a mistake? Email info@upvision.media with the page link — we check and correct reported errors.
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