It has been an exceptionally poor spring and many garden plants have been delayed in their development and readiness to flower.

Plants take their cue from the weather and the return of warmer conditions, and they hold back on progress if things do not suit them.

The photograph shown was taken on 4 April 2017, but azaleas had no sign of colour 10 days later than that this year. However, azaleas are robust plants and they just mark time and explode into growth when the air and soil warms up

The azaleas in question are the deciduous azaleas, part of the larger rhododendron genus.

Years ago these used to be treated under the name of azalea and, despite being correctly included in the rhododendrons, they are still called azaleas and few people call them rhododendrons.

They have very similar flowers and all their botanical names start with rhododendron. Most of the rhododendrons that we grow are evergreen, so it is bit of a leap to see these wonderful plants as such, and no harm to keep their old name as a commonly used one.

Whatever about the name, it is useful to know that these are rhododendrons and will have broadly the same needs as the rhododendrons.

This means they like acidic soil, well drained but capable of holding moisture in summer and well supplied with humus.

They also like reasonably good shelter and plenty of sunshine, but not dry soil. Although they like sunshine, and flower best in full sunshine, they are happy in some light shade, but not in constant shade.

Sunshine part of the day or light shade is satisfactory. They do not like to have big tree roots underneath as these dry out the soil too much.

Distinctive colour

The deciduous azaleas have a very distinctive colour range, tending towards yellow, and are generally very bright and vivid.

The colours are blazing hot red, candy pink, yellow, flame orange, marmalade and salmon.

Even though the colours vary greatly, they seem to blend with each other easily, often the mixture heightening the effect of the others.

The colour range is different to most rhododendrons which tend to heavier red, purplish and pink flowers, the colours veering towards blue or purple shades.

The azaleas are much more bright, with a range of citrus-like colours.

These colours go very well with spring shades. Being deciduous, they have new leaves that emerge at the same time as the flowers, expanding during flowering and just afterwards.

The leaves have lovely shades of bronze, copper and apple green, and they follow the colour of the flowers, dark for red colours, bronze for orange and green for yellow.

They also have the bonus of autumn colour by contrast, with the evergreen rhododendrons which do not change. Deciduous species are in general less prone to frost damage and these certainly are very hardy.

There are hundreds of named azalea cultivars, and many sold just as azalea mollis types. Nurseries find these plants very easy to raise from seeds that can be collected from mature plants.

These are open-pollinated and very varied, but can be an interesting mixture. They can be separated to some degree by the leaf colours even before they flower.

But there are the named varieties which are reliable. Golden Flare is a lovely yellow to deep ochre colour.

Balzac is a strong red, Christopher Wren is orange-yellow, Homebush is rose red, Strawberry Ice is a pretty pale red, Klondyke is golden-yellow, Gibraltar is orange-red. They are best chosen in flower.

Sparkling candytuft

The perennial candytuft, or iberis, is just coming into flower in the last week, a bit delayed. This is a most valuable little plant.

It looks a bit like a clump of little snowballs in flower. The flower clumps are clusters of tiny, white flowers. The colour is sparkling white, set off perfectly by the darker green leaves.

Sparkling candytuft.

It is part of the cabbage family and lasts for many weeks, the white often turning a bit pink or purplish as the flowers age.

It is easy to grow in any sunny spot with well-drained soil and the little rounded clump of stems is largely evergreen, so it looks great on a rockery or a bank. And it is remarkably weed-proof when established.

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