Rhododendron Horizon Monarch
Rhododendron Horizon Monarch
Rhododendron Horizon Monarch
Rhododendron
Magnificent plant. I had the pleasure of seeing it bloom this spring.
René , 02/11/2025
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This plant carries a 24 months recovery warranty
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Description
Rhododendron 'Horizon Monarch' is a bush of medium size with an impressive flowering: huge clusters of straw yellow flowers that emerge from peach-orange buds and create a very warm harmony! Despite its almost exotic appearance, this is a hardy and robust young plant.
The bush is dense and abundantly covered with beautiful dark green glossy foliage. It will reach a height and spread of 1.5 to 1.8m, and will be slightly wider than tall once fully grown. It is a vigorous and easy plant with beautiful growth, and we highly recommend it to all gardeners looking for a rhododendron "like no other"! This heathland bush will thrive in partial shade in a cool, humus-rich, and well-drained acidic soil. Like all yellow rhododendrons, it does not tolerate excessive watering, so it must be planted in a well-drained spot. The 'Horizon Monarch' rhododendron is hardy across a wide climatic range.
In April-May, its spectacular flowering consists of corymbs of 15 beautiful large flowers or more! The buds are reddish-orange with salmon undertones, and the inside of the flowers is straw yellow with a tiny bright red mark at the centre. The slightly fringed edges of the petals add extra relief. Thanks to the work of an American hybridizer from the Seattle area in the early 80s, we can now enjoy this magnificent variety, which brings a soft and warm colour harmony to the garden!
Rhododendron 'Horizon Monarch' can be used as a standalone or in mass plantings, especially with other heathland plants. It can be paired with Chinese azaleas, which share its warm tones, magnolias, Andromedas (Pieris), mountain laurels (Kalmia), Japanese maples with green or purple foliage...
Rhododendron Horizon Monarch in pictures
Plant habit
Flowering
Foliage
Botanical data
Rhododendron
Horizon Monarch
Ericaceae
Rhododendron
Cultivar or hybrid
Planting and care
Plant Rhododendron 'Horizon Monarch' in a partially shaded position, protected from cold and drying winds, in a fresh, humus-bearing and light soil with an acidic tendency. Like all plants that prefer acidic soil, it does not tolerate calcareous or heavy soils that become waterlogged in winter. Dig a hole three times larger than the pot. Soak the root ball in non-calcareous water and plant the bush at the level of the collar, in a mixture composed of 1/4 turf, leaf compost, gravel or pumice, and loam. Water generously and keep the soil moist in summer. Azaleas and Rhododendrons have a shallow root system, so they are susceptible to long periods of drought. Therefore, it is recommended to enrich the soil with humus and provide abundant watering during dry periods. Additionally, their root system is not very strong, which is why it is essential to lighten heavy soils with draining materials (gravel, pumice, clay pellets) at planting. Apply a mulch of shredded pine bark around the base of the bush every spring to maintain soil moisture while keeping an acidic pH. Maintenance involves removing faded flowers in summer and cleaning dead branches. Azaleas and Rhododendrons can sometimes be attacked by weevils that eat the edges of leaves and rootlets, as well as the infamous "rhododendron beetle" which rarely causes significant damage. You can use carbofuran as a treatment. Yellowing of the leaves (chlorosis) in Rhododendron indicates poor assimilation of iron in the soil and can lead to premature plant death. While limestone is often the cause, poorly drained soil or a deeply planted root ball can also explain the phenomenon.
Planting period
Intended location
Care
Planting & care advice
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Hardiness is the lowest winter temperature a plant can endure without suffering serious damage or even dying. However, hardiness is affected by location (a sheltered area, such as a patio), protection (winter cover) and soil type (hardiness is improved by well-drained soil).
The flowering period indicated on our website applies to countries and regions located in USDA zone 8 (France, the United Kingdom, Ireland, the Netherlands, etc.)
It will vary according to where you live:- In zones 9 to 10 (Italy, Spain, Greece, etc.), flowering will occur about 2 to 4 weeks earlier.
- In zones 6 to 7 (Germany, Poland, Slovenia, and lower mountainous regions), flowering will be delayed by 2 to 3 weeks.
- In zone 5 (Central Europe, Scandinavia), blooming will be delayed by 3 to 5 weeks.
In temperate climates, pruning of spring-flowering shrubs (forsythia, spireas, etc.) should be done just after flowering.
Pruning of summer-flowering shrubs (Indian Lilac, Perovskia, etc.) can be done in winter or spring.
In cold regions as well as with frost-sensitive plants, avoid pruning too early when severe frosts may still occur.
The planting period indicated on our website applies to countries and regions located in USDA zone 8 (France, United Kingdom, Ireland, Netherlands).
It will vary according to where you live:
- In Mediterranean zones (Marseille, Madrid, Milan, etc.), autumn and winter are the best planting periods.
- In continental zones (Strasbourg, Munich, Vienna, etc.), delay planting by 2 to 3 weeks in spring and bring it forward by 2 to 4 weeks in autumn.
- In mountainous regions (the Alps, Pyrenees, Carpathians, etc.), it is best to plant in late spring (May-June) or late summer (August-September).
The harvesting period indicated on our website applies to countries and regions in USDA zone 8 (France, England, Ireland, the Netherlands).
In colder areas (Scandinavia, Poland, Austria...) fruit and vegetable harvests are likely to be delayed by 3-4 weeks.
In warmer areas (Italy, Spain, Greece, etc.), harvesting will probably take place earlier, depending on weather conditions.
The sowing periods indicated on our website apply to countries and regions within USDA Zone 8 (France, UK, Ireland, Netherlands).
In colder areas (Scandinavia, Poland, Austria...), delay any outdoor sowing by 3-4 weeks, or sow under glass.
In warmer climes (Italy, Spain, Greece, etc.), bring outdoor sowing forward by a few weeks.
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