Rhododendron 'Horizon Monarch'

Common name: Rhododendron 'Horizon Monarch'

Description: Rhododendron 'Horizon Monarch' is a truly magnificent and large-flowered hybrid rhododendron of exceptional distinction, widely regarded by rhododendron specialists and discerning gardeners as one of the finest yellow-flowered hardy hybrids in cultivation, combining blooms of outstanding size, beauty, and unusual colouring with a vigorous and imposing garden presence that commands attention and admiration whenever it is encountered in flower. In mid to late spring, the enormous, well-rounded trusses — amongst the largest produced by any hardy rhododendron — open to reveal broadly funnel-shaped flowers of a warm, luminous pale yellow to soft primrose, each bloom suffused with a delicate peachy-pink flush at the margins and adorned with a subtle reddish-orange spotting in the throat that adds a jewel-like refinement to the already exceptional flowers. The sheer scale of the individual trusses, combined with the unusual and highly sought-after warm yellow colouring, creates a floral spectacle at the height of the spring season that is genuinely difficult to surpass in the rhododendron world. The large, handsome, evergreen leaves are a deep, lustrous dark green with an attractive leathery texture and a distinctive pale fawn indumentum on their undersides, providing a bold and polished year-round structural presence of considerable garden value. 'Horizon Monarch' develops over time into a large, broadly spreading, and imposing specimen of real grandeur that is most at home in a generous woodland garden setting, a large ericaceous border, or as a bold and statement-making specimen in any garden with the space to accommodate and appreciate its eventual stature. A rhododendron of the very highest order, suited to the gardener who seeks something truly exceptional.

Other benefits: exceptional large pale yellow flower trusses of outstanding size and beauty; unusual warm yellow colouring rare amongst fully hardy rhododendrons; attractive peachy-pink petal margins and reddish-orange throat markings; handsome large evergreen foliage with attractive pale indumentum on the leaf reverse; bold and imposing specimen value in larger woodland and garden settings; a collector's rhododendron of the very first rank

Wildlife attraction: bumblebees and other large-bodied pollinators

Height & spread (approx.) at 10 years: 2.5m x 2.5m

Position: partial shade preferred; dappled woodland light is ideal, providing shelter from strong midday sun which can scorch the large leaves and fade the delicate flower colouring; shelter from cold, drying winds is important; avoid frost pockets where late frosts may damage the large and particularly vulnerable flower trusses

Soil pH: requires acid soil; pH 4.5–6.0; will not tolerate alkaline or chalky conditions; benefits greatly from the incorporation of generous quantities of ericaceous compost and composted bark at planting; water with collected rainwater in hard water areas

Moisture: regular watering required, particularly when establishing and during dry spells; prefers consistently moist but well-drained, humus-rich, acid soil; a deep and generous mulch of composted bark helps retain moisture, suppress weeds, and maintain soil acidity; avoid waterlogging

Winter hardiness: hardy to approximately -15°C; thoroughly reliable throughout most of the UK in a sheltered position; the large flower trusses are particularly susceptible to damage from late spring frosts and a sheltered, frost-free position is strongly recommended