Do you love your acid loving plants?
By Sarah Wilson
Visitors to Kingswood love the sheer exuberance of the prolific Rhododendron ponticum that line our roads. Most gardeners will know that Rhododenrons – which incudes the evergreen Azaleas and the deciduous yellow Azaleas, are acid loving (or lime hating) plants and as such flourish in the acid soils of Kingswood gardens.
The soil in most Kingswood gardens is an acid loam – made over the centuries by the inclusion of leaf mould and pine needles from the oaks, Scots pine and larches. We know that our soil is acid as the main growth in uncultivated (and some neglected garden) areas is bracken and brambles.
The good health of our Rhododendrons is due to the fact that these plants only grow well in acid soils as they need to absorb iron to maintain the chlorophyll (green colour) in their leaves, and in an alkaline or chalky soil, the lime in the soil blocks the absorption of iron. They cannot thrive, the leaves go yellow (chlorosis) and eventually the plants die. Plants are similar to humans, who need to absorb iron from their food in order to make haemoglobin (the red colour in blood which carries oxygen around the body), plants need chlorophyll in order to make energy to feed their cells.
In areas with acid soil we can also grow other acid loving plants – Camellia, Pieris, Dogwoods, Witch Hazels, Holly, Magnolia, Acers, Viburnum and the summer flowering heathers. Heathers are in the same family as Rhododendron – the family Ericaceae. Of course we can also grow wonderful Hydrangea – more in the next newsletter.
On the whole acid loving plants are easy to look after but they do have a few needs –
In a dry summer and autumn they need water to ensure the buds set, as they have very shallow roots and will suffer from longstanding drought.
They may need to be hard pruned to reduce size – to preserve flowers for the next year you must prune your Rhododendron just after they have flowered – or you will have lots of green leaves but no flowers in June. All the rough barked Rhododendron and deciduous Azaleas can be pruned very “hard ” – back to the ground, and will regrow – and then be capable of control. Camellia can also be cut back to the ground and flourish. The “Species ” Rhododendrons are not so amenable to cutting back.
If you have a boundary of Rhododendron why not cut them back hard and see if you can rejuvenate them – they are so much more attractive than the native or Portuguese laurel that grow quickly but are quite rampant and do poison the soil and produce toxic berries.
As with all successful gardening the “right plant ” will always thrive in the “right place ” – here in Kingswood we have soil with a pH of 5-6 and acid-loving plants will thrive – why try to grow others?
Dr Sarah Wilson, a long time resident in The Warren, regularly opens her garden in the summer months with the National Garden Scheme.
To contact Sarah please click here