Rock Cress
kernera saxatilis
Also known as: ["Rock Cress","Saxifrage"]
Overview
A low-growing perennial herb native to rocky habitats, valued for its small, bright yellow flowers and hardy nature.
Benefits & Perks
["long-flowering","drought tolerant","wildlife attractant (bees, butterflies, birds)"]
Botanical Classification
| Phylum: | Magnoliophyta |
| Class: | Magnoliopsida |
| Order: | Brassicales |
| Family: | Brassicaceae |
| Genus: | Kernera |
| Botanical Name: | Kernera saxatilis |
Plant Characteristics
Basic Information
- Category: Flowers
- Suitable Location: rock gardens, alpine troughs, or sunny borders
- Suitable For:
- Is Weed: No
- Allergenicity: low
Environmental Needs
- Climate: {"temperatureRange":"–25–30°C"}
- Hardiness: {"zones":"3–7"}
- Misting: rarely required
- Drainage: Fast-draining to very fast-draining.
- Soil Type: Sandy, gritty, or loamy soil with excellent drainage.
Maintenance Level
- Maintenance Level: low
- Toughness Level: high
- Pruning Frequency: Annually in late winter or early spring before new growth begins.
- Pruning Intensity: Moderate; remove up to one-third of old growth if needed.
Care Details
Ideal Sunlight Coverage:
Full sun to partial shade (6–8 hours of direct sunlight daily). Adjust to partial shade in intense summer heat.
Sunlight Tolerance Tips:
Acclimate gradually to intense sunlight; protect from harsh midday sun; place in dappled shade during peak summer.
Care Requirements
Care Difficulty
easymoderate
Sunlight
full sun to partial shade
Avoid sudden light changes; provide morning sun; shield from hot afternoon rays.
Watering
every 2–3 weeks during active growth, less in winter
Water deeply but infrequently; avoid overwatering; ensure excellent drainage.
Soil
well-draining, rocky or sandy soil
pH: Slightly alkaline to neutral (pH 6.5–7.5).
Ensure soil dries quickly; avoid heavy clay mixes; amend with grit for drainage.
Temperature
Hardy in USDA zones 4–8; tolerates cold down to -30°C (-20°F); prefers cool temperatures (10–20°C / 50–68°F).
Protect from frost; avoid heat stress with shade; maintain cool conditions for best growth.
Fertilizing
every 4–6 weeks during spring and summer
Fertilize only in growing season; dilute fertilizer to prevent burn; stop in winter.
Propagation
Methods
Stem cuttings or division.
Step-by-Step Propagation Guide
- Take 4–6 inch cuttings.
- Remove lower leaves.
- Dip in hormone.
- Plant in medium.
- Keep moist and humid.
Best Time: Spring or early summer when plant is actively growing.
Environment
Warm (18–24°C / 65–75°F), high humidity, and bright indirect light.
Medium
Well-draining mix of perlite and peat moss or cactus mix.
Hormone
Optional but recommended for faster rooting.
Timeline
Roots in 3–6 weeks; establish in 2–3 months.
Tools Needed
Pruners, rooting hormone, small pots, well-draining medium.
Quick Tips
Use sterile tools; maintain humidity with a plastic cover; keep warm and bright.
Pruning & Repotting
Pruning Guide
Method
Pinch back tips; cut just above a leaf node or bud; thin out crowded stems.
Pruning Plan
Prune to maintain shape, encourage bushiness, and remove dead or weak growth.
Tools
Clean, sharp pruners or scissors.
Checklist
Sterilize tools; prune before new growth; remove dead wood; shape evenly.
Repotting Guide
Best Season
Early spring before active growth starts.
Pot Size
One size up (e.g., from 4-inch to 6-inch pot); ensure good drainage.
Method
Use fresh, well-draining soil; gently tease out roots; place in slightly larger pot with drainage holes.
Suggestions
Repot every 2–3 years or when roots fill the pot; beneficial for rejuvenation.
Checklist
Choose appropriate pot; prepare fresh soil; handle roots gently; water lightly after repotting.
Advanced Care Tips
Watering Mastery
Watering Checklist
Check soil moisture; water deeply; ensure drainage; reduce in winter.
How to Apply Water Properly
Water at the root zone until soil is moist but not waterlogged. Ensure excess water drains away completely. Water in the morning to allow foliage to dry.
Watering Schedule Tips
Water sparingly, allowing soil to dry completely between waterings. Reduce frequency in winter to once every 4–6 weeks.
Soil Improvement
Add perlite, coarse sand, or gravel to improve drainage; incorporate compost for fertility.
Temperature Stress Management
Signs of Temperature Issues
Leaf scorch in excessive heat; stunted growth or dieback in prolonged cold.
Cold Stress
Leaves may curl or drop; growth slows; roots can freeze in poorly insulated pots.
Solution: Mulch heavily in ground; insulate pots; move to sheltered location; avoid frost exposure.
Hot Stress
Wilting, leaf burn, or leaf drop; reduced flowering; soil drying too quickly.
Solution: Provide afternoon shade; increase humidity; water more frequently but still sparingly.
Fertilizing Guide
Fertilizing Checklist
Use diluted fertilizer; apply during active growth; cease in dormant season.
Fertilizing Method
Use a balanced, low-nitrogen fertilizer diluted to half strength every 4–6 weeks during spring and summer. Avoid fertilizing in fall and winter.
Common Problems & Solutions
Toxicity Warning
Cats
Non-toxicKernera saxatilis is not known to be toxic to cats. The plant does not produce compounds that are harmful to felines, and ingestion is not expected to cause adverse effects.
⚡ Toxic If:
if eaten
Dogs
Non-toxicKernera saxatilis does not contain known toxins that are harmful to dogs. The plant is not expected to cause any adverse effects if ingested by canines.
⚡ Toxic If:
if eaten
Humans
Non-toxicKernera saxatilis is not known to produce any toxic compounds that would cause adverse effects in humans. The plant is generally considered safe for consumption in small quantities.
⚡ Toxic If:
if eaten
Frequently Asked Questions
Q: Does Kernera saxatilis attract pollinators?
A: Yes, it is highly attractive to bees, butterflies, and other pollinators due to its bright yellow flowers.
Q: Is this plant suitable for rock gardens?
A: Absolutely, it thrives in rocky, well-drained soils and is ideal for rock gardens.
Q: How often should it be watered?
A: It is drought-tolerant and requires minimal watering, especially once established.
Quick Reference
| Family: | Brassicaceae |
| Care: | easy |
| Light: | full sun to partial shade |
| Water: | every 2–3 weeks during activ |
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