The Acid Garden
Customers are often concerned that acid-loving (ericaceous) plants require lots of expertise to grow and look after. So this month we thought we’d look at how easy these wonderful plants actually are, particularly those which bring early Spring colour and year-round interest to the garden.
What is Acidic Soil?
Acidity and alkalinity is measured using the scale of pH ranging from 0 to 14, with 7 being neutral and lower than 7 being acidic. The pH level is important because it affects the nutrients available to a plant from the soil. Ericaceous plants have adapted their mechanisms to be able to take up nutrients in acidic conditions and don’t do well when the pH is too high. In general, East Lothian soil is not naturally acidic but it’s quite easy to create an ericaceous planter or border simply by adjusting the pH with ericaceous compost and fertiliser.
In caring for ericaceous plants, bear in mind that naturally occurring acidic soils develop in areas of high rainfall or where there is much decomposition of organic matter such as in forests so you should try to mimic their native conditions by providing plenty organic matter and keeping the compost moist. It’s also advisable to monitor the pH levels as these can change over time and this can be done using an inexpensive pH kit or meter.
What’s your favourite?
Amongst the best-known acid-loving plants are Rhododendrons, Azaleas, Camellias and Pieris and this week we’re highlighting these ericaceous plants because they are particularly attractive in planters and borders in winter and the early part of the year.
Rhododendron & Azalea
There’s often confusion between Azaleas and Rhododendron – unsurprisingly because they have a great deal in common. Azaleas are actually a sub-group within the larger Rhododendron group and because of this you may find an Azalea labelled as Rhododendron, which is technically correct but of course can be very confusing for gardeners!
Azaleas can be either evergreen or deciduous and it’s believed that there are over 10,000 different cultivars. They’re shade tolerant and happy living under or near trees.
The deciduous Azalea mollis varieties flower on bare stems before the foliage appears. Being deciduous, many have striking foliage in autumn as the leaves turn before they drop.
The popular Azalea japonica (Japanese Azalea) is evergreen, hardy and compact with small dainty leaves and masses of small flowers in spring. They’re ideal for the front of borders or in rockeries and although they do well in containers, it’s important not to let them dry out! Rhododendrons are almost all evergreen and although there are a couple of deciduous Rhododendrons, these are not garden varieties. Although generally regarded as larger than Azalea, the Dwarf Rhododendron varieties are small-leaved, compact plants that can be difficult to tell apart from Azalaea japonica. Both Dwarf and Yakushimanum Rhododendron can be planted in containers, whilst the larger hardy hybrids are more suited to borders.
These are evergreen shrubs or small trees with glossy green leaves, and produce fabulous white, pink or red flowers in winter or early spring depending on variety. Native to Asia from the Himalayas eastwards to Japan, there’s thought to be some 3,000 hybrids. Common names include the Tea Rose or the Japan Rose. Ornamental Camellias were grown in Chinese and Japanese gardens for many centuries before being introduced to the UK in 1739 and became something of a fashion statement with high society in the 1800’s.
The Camellia sinensis is not a garden variety but it’s worth a mention because of its enormous economic significance. This plant produces the world’s tea leaves, and since tea is the most widely consumed drink globally other than water, it’s certainly of importance!
Although Pieris produce beautiful little flowers in spring similar to the Lily of the Valley, these small to medium sized evergreen shrubs are primarily grown for their attractive foliage, particularly in spring when new growth forms. Pieris japonica has dark green foliage and the new spring foliage starts as bronze in colour before maturing to green.
The cultivar Pieris ‘Forest Flame’ produces particularly vibrant, eye-catching bright red foliage in spring, hence the name.
Pieris ‘Mountain Fire’ also produces striking new spring foliage with the added attraction of its variegated leaves which provide interest all year round.
Hopefully this brief introduction to ericaceous plants has given you some ideas for your own acid garden, and as always if you have any questions, our plant team are happy to chat gardening.