Millais Nurseries
Rhododendron Catawbiense Boursault INKARHO
Item: ICATB
In stock
May
Purple
Below -20 °C
175-200cm
Not Scented
No
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(H7) Long lasting lilac purple flowers with few markings. Late May flowering in a dense truss. A vigorous, very tough old variety, dating from before 1850, and hardy to -30C. Height 175-200cm in 10 years.
Plant with plenty of good ericaceous compost to aid establishment.
- Recommended for: Hedging/screening.
- Easy to grow.
- Ideal position: Most garden situations.
- Habit: Dense.
- Group: Hardy Hybrid.
- Tolerant of some wind.
- Ideal soil: pH 4.5 to 6, and up to pH 7.5.
- RHS Hardiness Rating: H7.
Good to know
These are the plants which we have featured in our recent RHS Chelsea Flower Show exhibits, with extensive reporting on the BBC Chelsea TV programme. Interest from new customers around the country has been exceptional, and gardeners have been delighted to learn that they can now grow their favourite plants on most garden soils.
The revolutionary new ‘Inkarho’ lime tolerant rootstock is particularly recommended for growing rhododendrons on neutral clay soils, up to pH7. This patented rootstock was developed from a rhododendron growing in a German lime quarry, and has been the subject of an extensive 20 year breeding and testing programme. They are grown under licence in Germany, and are some of the few plants that we have to buy in. Choice tall hybrids and compact yakushimanum varieties are grafted on the rootstock enabling them to be grown in a much wider range of soil types than ever before. They are hungry plants and require more feeding than other Rhododendrons to keep their foliage a healthy dark green. We recommend our own recipe Millais Nurseries Slow Release Fertilizer and plenty of good Ericaceous compost for best performance. Failures are rare, but occur when there is insufficient soil preparation, and insufficient feed. Without feed, the plants will start to wither and the foliage will go yellow.
The varieties selected are all tough and will flower from a young age. For a guide to plant spacing, use the height we give in 10 years as a guide to the distance between each plant. Plant no deeper than the top of the rootball, and dig in plenty of good ericaceous compost around the sides. Feed at the rate of a teaspoon of ericaceous slow release fertilizer per plant at the 4 litre size, rising to a tablespoon per plant for a 12 litre plant, and a small handful for a more mature specimen. For growing in pots, please select the lower growing yakushimanum hybrids, and use good Ericaceous compost
Please note: Some varieties are wider than their height, especially yakushimanum hybrids. Specimen size plants (eg 80-90cm) will be measured by their largest measurement which could be the spread of the plant.
For further advice, For further advice, see here
The Basics
Ideal soil
Acidic soil, good organic content, pH 4.5-6.0. Inkarho range of rhododendrons will tolerate soils up to pH7.5
Sun or Shade
Light dappled shade is best for most varieties.
Shelter
Refer to hardiness rating. Give young plants protection.
Avoid close to trees, roots, invasive weeds, walls, hot patios, dry banks and waterlogged soils. Do not use weed matting or stone mulch
Plant spacing
Use the height shown in 10 years as a guide to the distance between each plant. Allow room for plant to fill out. If planting closer for instant impact, be prepared to move plants after a few years.
Compost
- 3 litre pot, dig in 10-20 litres of ericaceous compost.
- 7.5 litre pot, dig in 20-30 litres of ericaceous compost.
- 70-80cm specimen, dig in 60 litres of ericaceous compost.
- 100-120cm specimen, dig in 120 litres of ericaceous compost.
Planting depth
Plant high in the ground, with the top of the rootball visible.
Feeding
Slow-release ericaceous feed recommended in March and straight after flowering.
Mulch
Recommended every few years.
Water
The key ingredient! Keep moist all season, especially the critical time at end of June for flower bud initiation. Tap water is better than no water. Heavy dose at least once per week in dry weather.
Drainage
Ensure good drainage in winter, especially with yellow varieties. Avoid waterlogged sites.
Pruning
Not normally required. Tidy wayward shoots after flowering. Evergreen azaleas and Bloombux can be clipped into a low hedge.
Deadheading
Remove old flower-heads, particularly on young or weak plants.
For further advice see here
Size Guide
