Ravishing rhododendrons

We are now in the thick of the rhododendron season and it lasts for months. Although each variety is only in bloom for a few weeks, with careful selection you can have flowers from before April, through the crescendo in May and early June even into July and beyond.

The best time to plant most evergreens is in April so this is a perfect excuse to buy a rhododendron in bud or even starting to bloom.

Recent changes in classification mean that the plants we know as azaleas are strictly rhododendrons but, as gardeners, there are differences that mean it is easier to call the small-flowered deciduous and evergreen rhododendrons azaleas as we are used to doing.

Japanese azaleas such as ‘Matsugiri’ are attractive, evergreen shrubs that are dazzling when in bloom

What they all have in common is that they hate lime in the soil. They need acidic soil. So if your hydrangeas turn pink instead of blue you will have problems growing most rhododendrons in your soil.

But you can grow them in pots. To be honest, this is not the easiest way to grow rhododendrons and azaleas, but it can be done. You will need a pot (not concrete, which contains lime) and some ericaceous (acid) compost. The other thing you must remember is that you will have to monitor watering carefully. Rhododendrons have thick, waxy leaves that will not wilt when the compost is drying out and it is too easy to forget to water them in summer. The results of your neglect will only show many months later when the leaves droop and the plant slowly dies.

Dappled shade suits most azaleas and rhododendrons best

in the garden, rhododendrons prefer a light soil (sandy) with the addition of plenty of organic matter. Once they are established they will tolerate some dryness in summer but they will not survive in wet, heavy clay soil.

They vary hugely in size and, if just starting out, the Japanese azaleas are probably the best because they are low and spreading and none get too big. They also spread to form good ground cover. If planted under the canopy of tall trees it can help prevent frost damage to any early flowers.

Deciduous azaleas have dazzling flowers and brilliant autumn colour. Some are scented

The deciduous azaleas, which lose their leaves autumn, are generally upright when young and flower prolifically in May and June. They like a sunny spot and are perfect companions to hostas and bluebells.

The more traditional rhododendrons also vary a lot in size and form. In small gardens the ‘Yakushimanum’ or ‘Yak’ hybrids are a good choice, growing slowly into dense domes. Their flowers are in dense clusters too, usually in shades of pink.

Yakushimanum’rhodos have a compact habit and showy flowers

The big, hardy hybrid rhododendrons vary in size but some can become large and more than 3m (10ft) high and wide. It is these that have the largest and most spectacular flowers and make a real show in the garden. Most will cope with full sun in the garden provided they do not dry out in summer. They will flower more abundantly in sun and have a looser habit, with fewer flowers in shade.

Rhododendron ‘Tequila Sunrise’

When buying and planting now you will need to water them in any dry weather for the first season.

Soak the plant well before planting. Dig out a large hole, at least twice as wide as the pot. Mix in some compost, or acid (ericaceous) compost with the soil in the hole and the excavated soil. Place the pot in the hole to check depth, then remove it and water the hole well. Plant, gently firming the soil around the roots, level the soil and water well. You can the mulch with compost or composted bark to help conserve soil moisture but you will still need to water.

Weekly reminders

Lots of vegetables can be sown now, outside in the garden or in raised beds. Sow turnips, radish, rocket, peas, spinach, lettuce and other salads, beetroot and more.

Sow French and runner beans, sweetcorn and squash in pots inside to plant out next month.

Sow hardy annuals outside where they are to bloom.

Keep weeds under control. Hoe off annual weeds but dig up perennials like dandelions, ground elder and bindweed.

Weed and feed your lawn if it is warm and the soil is moist

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