How to plant a Rhododendron
Site selection: Most rhododendrons will take sun or shade, but semi shade is best. Select a position with moist acidic soil (pH 3.0-6.0), and avoid planting close to large trees, hedges and shrubs which will steal all the soil moisture. Choose a position with enough room for the plant to grow – the height we give at 10 years is also a guide for your plant spacing. Most Rhododendrons need to be planted at least 2m from a tree. Dry banks and disturbed soils can be particularly inhospitable. Avoid open lawn situations or too close to walls and fences. Also ensure there is good winter drainage, as Rhododendrons can not survive with their feet in saturated soils. Yellow varieties in particular need good drainage.
Site preparation: Always clear any perennial weeds and grasses from the site, and dig a wide hole, at least 2-3 times the width of the rootball. Do mix in plenty of good Ericaceous compost or your own well rotted leaf mould, pine needles or compost. Never use animal manures which are too strong for sensitive Rhododendrons, or mushroom compost which is too limey. Even on good soils we recommend at least 10 litres of compost for a dwarf plant, and 20 litres for a larger hybrid. Remember, the better you plant, the more you will be rewarded.
Planting: Do not plant too deep (see diagram). Rhododendrons hate being planted deeper than the top of the pot. The number one reason for failure is when the lower stems have been buried below soil level. Also avoid mulches around the stem. Give your plant a dose of slow release ericaceous plant food (we recommend Miracle Gro Slow Release Rhododendron Plant Food). We do not recommend weed suppressing matting; Rhododendrons are surface rooting and any matting can spoil soil aeration and drainage.
Feeding: Just like we all need regular meals, so do young Rhododendrons! Give your plants a dose of slow release ericaceous plant food which should be applied once a year in March. We do not recommend bone-meal which has too much calcium. When planting in the autumn, (the best time) a small dose of super-phosphate will encourage good root growth.
Maintenance: Ensure that your plant has plenty of water during the summer, especially on dry sandy soils. Rhododendrons are shallow rooting, and will not compete with nearby deep rooted trees and shrubs without additional water. Avoid perennial weeds and grasses growing around the plant. Straight after flowering, pinch out the old flower heads to encourage healthy new growth and energy for next year’s flowers, and to nicely ‘groom’ your plant for the summer. In the autumn consider a light mulch (around 3cm) to prevent weeds, conserve moisture and feed the plant. Enjoy!