I WAS watching the Masters golf tournament a couple of weeks ago and was marvelling at the magnificent landscape that has been created at the course in Augusta, Georgia. Apparently it was built on the site of an old plant nursery hence the plant names that are given to each hole. With Azaleas, American flowering dogwoods, Camellias and Magnolias growing on the course it would suggest that the soil there is on the acid or ericaceous side. This means it has a low soil pH reading, probably below 6.5. With a neutral soil being 7.0, anything below 6.5 makes it suitable for growing these acid loving plants. A pH of over 7.0 means the soil contains lime which can render some nutrients unavailable to ericaceous plants causing yellowing - lime induced chlorosis- on the leaves. This can be remedied by careful planting and applying sulphur or iron.
I have never gardened in an area that is totally suitable for growing ericaceous plants but with so many of this type being so desirable I have tried to create localised conditions that enable me to do so. This year has been particularly tempting as the Camellias, Magnolias and Pieris have been particularly spectacular in flower.
The first step to attempting to grow these plants is to get some idea of what the pH of your soil is. You can send samples away for analysis but this seems to be a little overkill for the average garden. You can also buy simple kits from garden centres that will give you a ballpark reading. They work on a colour chart and only show increments of whole units, 4.0, 5.0, 6.0 etc. I think this is adequate for the home gardener, to be honest. Also look around at what is growing in other peoples' gardens, this will give you an idea of what is doing well in your own locality.
I'm working on the basis of between 6.5 and 7.0 at home which means I have to put a little effort into planting ericaceous species which would prefer 5.0 to 6.5 although anything below 7.0 and you are on the right side of the chart. When planting any acid loving plant I always go to the effort of creating an extra large planting pit, one metre across. I then dig out thirty centimetres depth of soil and dig over the bottom of the hole another fork depth incorporating two buckets of ericaceous compost, a slow release ericaceous fertiliser and a handful of sulphate of iron. I then mix the same again into the excavated soil and backfill the hole. Once planted, I mulch with a fine bark, this helps stop weather compaction of the soil which ericaceous plants dislike. These plants like their roots in moist cool so this also does the trick.Top dressong annually with a handful of each fertiliser again each April will keep the ph down.
Lime hating plants fall into a varied spectrum of lime tolerance even within their genera. Camellias tend to be quite lime tolerant compared with many other acid loving plants. Good choices are C. 'Spring Festival' semi double flower, shell pink and C. japonica 'Adolphe Audusson which is an excellent red.
Magnolia's lime tolerance varies a lot. M. stellata [Star Magnolia] with its starry white flowers seems happy everywhere as does the omnipresent M. x soulangiana, with its candle flame shaped flowers in white or pinks. This is the plant I most get asked for in my garden designs. The awe-inspiring M. macrophylla is more choosy but with leaves at 60 centimetres in length and large white flowers it is worth the effort for the enthusiast. It needs a very sheltered spot to do the leaves justice. Magnolia x grandiflora is a favourite of mine. It was traditionally grown against a warm wall, it is evergreen and has large fragrant cream flowers in October.
Rhododendrons and Azaleas are another reason I try my best to accommodate some ericaceous plants in my garden designs. They are so stunning in flower. R. 'Cunnigham White' is doing well for me in my own garden too. There are new varieties of Rhododendrons that claim to be lime tolerant. I would take that with a pinch of salt or should I say sulphate of iron. I tried some a few years ago without great success so unless they have improved I would plant them as lime hating to be honest.
Other magnificent acid loving plants that are worthy of the effort include the Eucryphias. E. cordifolia which is the most lime tolerant and one of the loveliest. Also our very own E. x nymanensis ' Mount Usher' raised in the famous Wicklow gardens. Pieris
“With a little bit of care and attention these lovely plants will repay you for years to come.”
are very popular as well- P. 'Forest Flame' with its disinctive red young growth and clusters of drooping white flowers is deservedly much planted. Variegated cultivars like P. 'Flaming Silver' are equally beautiful.
Finally getting back to Augusta and the flowering dogwoods, while they are not strictly ericaceous they don't like very limey soils but don't mind the acid loving treatments. Of these, Cornus kousa is a lovely species from Japan with creamy bracts and C. florida 'Cherokee Chief' is of American origin with pink bracts. Both have good autumn colour. If you are in the market for something adventurous look out for C. capitata which is evergreen and has yellow green bracts and comes from the Himalayas.
With a little bit of care and attention these lovely plants will repay you for years to come.
The wonderful golf course at Augusta, Georgia. Inset: Flowering dog wood, Cornus kousa