How to grow ericaceous plants » Ashwood Nurseries:
Ericaceous plants include Rhododendrons, Azaleas, Camellias, Heathers, Pieris, Blueberry, Cassiope, Eucryphia, Enkianthus, Fothergilla, Gaultheria, Leucothoe, Nyassa, Kalmia, Pseudowintera, Styrax and Vaccinum.
Ericaceous plants require acidic to neutral soils (pH7 or lower) and generally will not thrive in more alkaline conditions (i.e. high in lime, pH7.5 or higher). They are mostly plants of woodland, heath or mountain-side so require moist but well drained soils that are rich in organic matter.
Most ericaceous plants prefer the dappled shade and shelter of other trees and shrubs and are also useful subjects for a sheltered North facing border. They are tolerant of more sunny exposures as long as the soil remains moist. Smaller leaved rhododendrons, most azaleas as well as blueberries and heathers prefer a slightly sunnier position, perhaps shaded from the sun when it is at its strongest in the early afternoon. Rhododendron yakushimanum and its cultivars are very tolerant of cooler, more exposed positions.
Our ericaceous plants are generally completely hardy, tolerating temperatures down to -15 ° F (-25 °C). Those plants marked slightly tender should be given a very sheltered position. Some care is needed in the siting of early flowering subjects to avoid their blooms becoming marked by late spring frosts and for these it is best to avoid an east-facing site. Likewise, plants that produce spring foliage colour (e.g. pieris) are probably better placed in a southerly or westerly aspect, sheltered from sun and cold winds by surrounding evergreen shrubs.
All ericaceous plants are surface rooting with very fine roots so extra care is needed when planting. Plants grown in containers can be planted out at any time of year; provided that the ground is not frozen.
Prepare an area 5-6 times larger than the pot size: work organic matter (such as leaf mould, peat or good quality ericaceous compost) into this area to form a nice friable mixture. Mushroom compost and manure are not suitable because of their lime content, nor should fertiliser be applied at this stage.
Water the plant in its pot thoroughly, leaving to soak for a few minutes. The correct planting depth is very important as ericaceous plants will not thrive if planted too deeply: plant to the same depth as the compost in the container, barely covering this with the lightest layer of soil.
Place the plant in its planting hole and then firm in lightly with the fists. If necessary, particularly with a larger plant, drive in a stout stake away from the root ball and tie the plant to it.
Finally, water the plant by giving it a thorough soaking at the roots. A light sprinkling of water is a waste of time, has no benefit to the plant and in fact can be detrimental to the roots
Continue to water during the first growing season and subsequently during very dry weather otherwise the fine roots will suffer. All weeds are best removed by hand whilst still young as hoeing and forking too close to the plants may damage the roots.
An annual mulch of peat, leaf-mould, pine needles or composted bark is beneficial. Spread this material in a 1-2 inch (2.5-5cm) band 6 inches (15cm) from the base of the plant. Never mulch too close to the stem of the plant as this may cause the bark to rot. Avoid using fertilisers other than a very light application of blood, fish and bone in May only.
After flowering, the larger flowers of rhododendrons, azaleas and camellias can be dead headed by carefully breaking out the truss of seed heads before the leaf buds start into growth, but take great care not to damage these new buds.
How to grow Ericaceous Plants on Alkaline Soil
If your soil is alkaline, we would suggest planting into large containers or purpose-built raised beds.
Containers should have a drainage hole, filled with good quality ericaceous compost and their position in the garden chosen carefully to take into account their cultural requirements. You must be prepared to be diligent with watering.
Raised beds should be raised at least 6 inches (15cm) above surrounding soil to prevent any alkaline water flowing into them. The walls can be built of most materials although we would discourage the use of limestone or concrete blocks. Some materials that harmonise particularly well with this form of plantings include old railway sleepers or half round timber edging. The beds should be filled with an ericaceous mix either a good ericaceous potting compost, or a mixture or two parts acid loam (shredded Mendip Loam being ideal) six parts peat of leaf-mould and one part sharp flint or quartz grit (not limestone chippings) of between ¼ and 1/8 inch. (3-6mm)
Pests and Diseases
Ericaceous plants are rarely troubled by pests and diseases except for aphids (green fly) which distort the young growths: these should be controlled either with a systemic insecticide or regular treatments with a proprietary soap treatment. Mildew, if it occurs, is best controlled using a systemic fungicide.
Sometimes, the roots and underground stems may be nibbled by vine weevil grubs. The adult weevils leave irregular-shaped notches in the leaf margins during the summer while the white legless grubs are likely to be found among the roots which they eat, causing the plants to wilt in severe cases. “Provado Vine Weevil Killer” is an effective control for plants in containers.
More! Make an Ericaceous Soil Bed for Acid-Loving Fruits:
Espoma's "Soil Acidifier."
It contains sulfur, derived from elemental sulfur and gypsum.
You can find this organic goodness at any respectable garden center. Application is a breeze: First, grab a measuring cup...
And fill it with the acidifying granules.
Then pour the granules in a circle around the drip line of each shrub.
The drip line is the outermost edge from which water would naturally drip from the plant.
Feeder roots are concentrated there.
Rates. For young shrubs, use about 1 1/4 cups acidifier. For larger shrubs, use 2 1/2 cups.
Repeat the procedure every 60 days or so, or until you achieve the correct pH for your blueberries -- 4.6 to 5.5. Watering-in.
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