What hardiness zones is Primula kisoana suitable for?

Primula kisoana is the Kiso primrose, growing 4–8 inches (10–20 cm) tall and spreading 6–12 inches (15–30 cm) per plant by underground stolons. Pink to rose-pink flowers 0.75–1 inch (18–25 mm) with notched petal tips in umbels of 3–8 on hairy stems 4–6 inches (10–15 cm) in mid to late spring. A white-flowered form ('Alba') is also cultivated. Rounded palmately lobed (maple-like) softly hairy leaves 2–4 inches (5–10 cm) — the lobed leaf shape is unusual for Primula, as most species have simple unlobed leaves. Spreads by underground stolons to form ground-cover colonies — one of the few Primula species that spreads vegetatively rather than relying solely on seed. In the primrose family (Primulaceae). The stoloniferous habit makes P. kisoana one of the easiest woodland primulas to establish in temperate shade gardens. Native to Japan (Honshu — the Kiso Mountains and surrounding regions in central Japan), growing in moist mountain forest understory. The foliage persists through summer in cool moist conditions; in hot dry climates the plant goes dormant by midsummer. Consistent moisture during the growing season. Partial shade to full shade. Non-toxic. Deer-resistant. Zones 4–8. Growth rate is moderate (via stolons).

Native Range

Native to Japan (Honshu), specifically the Kiso Mountains and surrounding regions in central Japan, growing in moist mountain forest understory.

Suggested Uses

Grown as a shade groundcover in zones 4–8. The stoloniferous habit forms colonies — one of the easiest woodland primulas. Companion to Hepatica, Erythronium, and ferns. Non-toxic. Deer-resistant.

How to Identify

Identified by pink (or white) flowers with notched petal tips in umbels above softly hairy palmately lobed (maple-like) leaves. The lobed leaf shape (unusual for Primula) and the stoloniferous spreading habit are species identifiers. Most Primula species have simple unlobed leaves and do not spread by stolons.

Appearance

Size & Dimensions

Height4" - 8"

Width/Spread6" - 1'

Reaches mature size in approximately 2 years

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~3 weeks

Spring

Mid to late spring (April–May), lasting 2–3 weeks. Pink or white flowers in umbels of 3–8. The foliage persists through summer in cool moist conditions; dormant by midsummer in heat.

Detailed Descriptions

Flower Description

Pink to rose-pink (species) or white ('Alba'); 5-petaled with a notched petal tip, 0.75-1 inch (18-25 mm), in umbels

Foliage Description

Medium green, rounded, palmately lobed (maple-like), softly hairy, 2-4 inches (5-10 cm)

Growing Conditions

Sun Requirements

Partial Shade Full Shade

Requires 1-4 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.0(Neutral)

357912

Soil Types

loam peat

Drainagewell drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

1-2 years

Care & Maintenance

Care Guide

Partial shade to full shade. Humus-rich well-drained soil. Consistent moisture — dormant in hot dry conditions. Spreads by underground stolons (one of the few vegetatively spreading primulas). Non-toxic. Deer-resistant. Zones 4–8.

Pruning

Remove spent flower stems after bloom. The foliage dies back naturally when the plant goes dormant. No other pruning needed.

Pruning Schedule

fall

Maintenance Level

very low

Container Growing

✓ Suitable for container growing

Minimum container size: 2 gallons

⚠️ Toxicity Warning

Non-toxic