A heather bed should be positioned in full sun, away from deciduous trees, and if possible, sited so that the main view is from the south, as foliage heathers always colour better on their southern side. The bed should be informal in shape and preferably, contain no straight lines.
Clear the site of all weeds, particular care being given to perennial weeds such as bindweed and ground elder.
On heavy clay soils, break up any panned subsoils and incorporate copious amounts of well soaked sphagnum moss peat or any other fibrous soil conditioner. Sand, pea grit, or perlite can also be added to improve soil texture but avoid the use of sedge peat and spent mushroom compost unless you are planning to plant lime tolerant species.
Estimate the planting area in square metres (square yards), deducting one square metre (square yard) for each conifer included. Then multiply by five (four) to obtain the number of heathers required. Use no more than one conifer per five (four) square metres (square yards) and use those attaining a height of one to three metres (yards) in ten years. Plan to use about ten different heather varieties but reduce this number if necessary to ensure that the minimum number of plants of a particular cultivar is three.
Some species of heather require acid soil conditions to thrive, whereas others will grow in most soils. Therefore, before you can decide which heathers to grow you do need to know the alkalinity of your soil. The degree of alkalinity or acidity of your soil is measured on a scale of 0 to 14 known as the pH scale. Soils vary from very acid with a pH scale of 3.5 to very alkaline with a pH just over 8. Ericaceous plants require significant quantities of iron, which in soils with a pH above 6.5 is rendered virtually insoluble and hence iron deficiency sets in, causing the plant to yellow and then die.
If you do not know your soil pH, purchase a soil testing kit. Kits are available at most Garden Centres. Try to obtain the type containing test tubes already filled with the testing liquid. Dry the soil very slowly (overnight) before testing, to get the most accurate result. Avoid using pH probes which require no battery, also widely available in Garden Centres, as these do not produce sufficiently accurate results.
The species chosen, therefore, will depend, to some extent, on whether the soil is acid or alkaline (see also "Choosing heathers". If your soil is acid, you can grow any heather cultivars.
For those whose pH is greater than 6.5, the best advice is to restrict your choice to Erica carnea, Erica x darleyensis, Erica erigena, Erica manipuliflora, Erica vagans and any of the tree heaths with the exception of Erica arborea. For those keen on hard work, the other species may be grown with difficulty by adopting one of the methods outlined below.
Normally the best method is to import acid soil and create a 60cm deep bed on top of your existing soil. Acid soil is usually cheap, as it often cannot be sold as good topsoil. Edge the bed with peat blocks or allow the bed to drop to normal soil level, in which case, plant lime tolerant plants around the edge, such as Erica carnea.
The next approach is watering twice a year with an iron compound which remains soluble in the presence of calcium. Such a compound is chelated iron or sequestered iron sometimes sold under the trade name Sequestrene. Heavy soils will still need conditioning by the addition of humus such as sphagnum moss peat or fine bark.
The third approach is to dig flowers of sulphur into the bed, which has the effect of tying up calcium, allowing the iron which is already in the soil, to become more soluble. In clay soils, use 4oz per square metre (square yard ) for every one pH drop required and add peat or fine bark to improve the condition of the soil. In sandy soils, reduce the rate to 1oz per square metre (square yard).
© The Heather Society, 11 November 2009