rhododendron or azalea?
Rhododendrons are amongst the most popular of garden plants - I challenge you to find a garden in the area that doesn’t have one squashed into a corner somewhere! There popularity is well deserved. Very few other evergreen shrubs offer such a spectacular display in early spring and the majority of deciduous azaleas deliver a double whammy of stunning spring flowers followed later in the year by fiery autumn colour.
But did you know the name ‘azalea’ is a bit of a misnomer? You may see a plant labelled, for example, Azalea ‘Harvest Moon’ but strictly speaking, azalea is not a true genus. Taxonomically, all azaleas and rhododendrons are classified as belonging to the same genus, Rhododendron. Broadly speaking, the name azalea is used to distinguish deciduous rhododendrons with funnel shaped flowers and 5 stamens while most people know rhododendrons as larger, evergreen shrubs with bell shaped flowers and 10+ stamens. To confuse matters further, some azaleas can hang onto their leaves over the winter depending on the growing conditions.
Most naturally occurring species of rhododendron are native to West and Central China and southeast Asia. They are mostly woodland and alpine plants that thrive in cool, humid conditions in partial shade - hence the reason they do exceptionally well in these parts. Deciduous rhododendrons can take significantly more sun than their evergreen counterparts but both need well drained, acidic soil to thrive. They grow best in a soil pH range of 5.0 - 6.0. Around here, the soil tends to be on the acidic side of neutral but you’ll want to add plenty of acidic organic matter to the planting hole (and as a mulch in subsequent years) to ensure they’re at their happiest. Composted pine needles, well rotted tree bark and composted bracken are good sources of ericaceous materials. Failing that a bag of Ericaceous compost from the garden centre will do the trick.
Rhododendrons don’t need much pruning. Evergreen species will come back after a hard prune but this is normally only needed to tame a plant that has outgrown its spot (not truly the fault of the plant - right plant, right place and all that jazz). Occasionally, they may need some light (and I mean light) pruning to correct form and remove a wayward branch or broken/damaged stem. If this is the case, prune only after flowering has finished and don't get too carried away with the secateurs otherwise you may affect next years flowers. Like all flowering plants, a little deadheading of spent flowers will tidy things up and encourage the production of a few more flowers.
So the next time someone refers to a deciduous rhododendron as an azalea, you can politely correct them though they may carry on regardless - I’ve been arguing the point for years. I guess its harmless but botanical correctness is an obsession of mine. Don’t get me started on geraniums that are actually pelargoniums!