Nova Zembla Rhododendron
Rhododendron 'Nova Zembla'
Ericaceae · broadleaf evergreen shrub · introduced
Last updated
An upright evergreen shrub reaching 5 to 6 feet in 10 years and 8 to 10 feet at maturity. Bright red flowers with bold black spotting in ball-shaped trusses. Midseason bloom. A catawbiense-type hybrid of 'Parsons Grandiflorum' crossed with a hardy red hybrid, bred by Koster & Sons in the Netherlands (RHS 58).
Exceptional cold hardiness to -25°F (Zone 4b-8a) places this among the hardiest red-flowered rhododendron hybrids in commerce, usable in zones where most red cultivars fail. The catawbiense backbone delivers toughness under harsher exposures than typical red-flowered selections. Full sun to part shade on acidic, well-drained soil (pH 4.5-6.0). Twenty-one diseases and 15 pests documented at the genus level. All parts contain grayanotoxins and are toxic if ingested.
Quick Facts
Root Colonization (Spring–Fall)
Infection at Bud Break
Apothecia Formation & Spore Release
Aecial Stage (Alternate Host)
+ 13 more — see full disease and pest lists below
Phenological Calendar
| Stage | Typical Window |
|---|---|
| Bud swell BBCH 01-03 | Mar 15-Apr 15 |
| Bloom start BBCH 61 | Apr 15-May 1 |
| Full bloom BBCH 65 | Apr 25-May 10 |
| Bloom end BBCH 69 | May 5-May 25 |
| Bud set BBCH 55-59 | Jul 15-Sep 15 |