Agapanthus 'Northern Star'
A free‑flowering, deciduous cultivar selected for dark violet‑blue umbels with a fine purple stripe on each petal. Plants make dense clumps and send up tall, stiff stems in mid to late summer. It is among the hardier agapanthus in gardens and is commonly listed for USDA zones 6 to 9 with winter mulch and good drainage. All parts are harmful if eaten; handle with care if the sap contacts skin.
At‑a‑glance
- Group/Class: deciduous agapanthus cultivar
- Height × spread: 30 to 40 in (75 to 100 cm) × 18 to 24 in (45 to 60 cm)
- Bloom window: mid to late summer
- Color & flower form: dark violet‑blue, rounded umbels with purple petal stripes
- Fragrance: 0 none
- USDA hardiness: 6 to 9; mulch and provide drainage in cold sites
- Breeder / Year / Origin: unknown
- Awards/registration: RHS Award of Garden Merit
- Cut‑flower notes: upright, firm stems; typical vase life about 7 to 10 days
- Pet safety: avoid
How it differs
- Notably cold‑tolerant compared with many evergreen types.
- Distinct purple stripe on petals adds depth of color.
- Sturdy, upright scapes support well‑rounded heads.
Strengths
- Reliable flowering in cool‑summer regions.
- Useful for mid to late‑season color.
- Strong stems for arrangements.
- Performs in borders and large containers.
Care in one minute
- Full sun in most climates; light afternoon shade inland.
- Soil: fertile and well drained; raise beds or add grit where winters are wet.
- Water regularly through bud formation, then moderately.
- Feed in spring with a balanced fertilizer; avoid heavy nitrogen.
- Remove spent stems; divide congested clumps in spring.
- In zones 6 to 7, apply a deep, breathable mulch after the ground cools.
Watch‑outs
- Requires sharp drainage in winter, especially in zone 6.
- Shade and rich nitrogen feeds can reduce flowering.
- Slug and snail feeding on young leaves.
Best uses (tags)
borders, cutting, containers, cold‑tolerant, late season, pollinators
Provenance note
Recorded by the Royal Horticultural Society and protected by a U.S. plant patent; widely distributed in North American horticulture.
References
- Royal Horticultural Society – Agapanthus ‘Northern Star’ (AGM) profile
- US Plant Patent PP20957 – ‘Northern Star’ (public record)
- Missouri Botanical Garden – Agapanthus (group) profile
- UC ANR – Agapanthus spp. safety note
Written by: Your Flowers Guide editorial team
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