What composts can I use for propagation?
How do I propagate heathers by seed?
How do I propagate by layering?
How do I propagate using cuttings?
What composts can I use for growing heathers?
What is the best way to arrange a heather garden?
How do I select heathers for a particular soil type?
How and when should I prune my heathers?
What are the best places in which to plant heathers?
How do I take care of Cape heaths?
What are “painted” heathers?
A compost into which rooting can take place can be prepared from 3 parts sphagnum moss peat (do NOT use sedge peat as this can often have a high pH) and one part of horticultural perlite. An acid gritty sand can be used instead of perlite where available but it must be acid. This applies even for the propagation of heathers which would normally grow in any soil, as an acid medium will improve the rooting yield. There is no need to add fertiliser at this stage, in fact, the yield is likely to be higher if none is added.
If horticultural perlite is being used add water to the perlite as instructed by the manufacturer, otherwise for easy mixing and subsequent handling, there is no need to add extra water at this stage.
Heathers can be propagated by layering, cuttings, or by seed.
To increase your stock of heathers, they must be propagated vegetatively to remain true to the parent plant. Heathers produced from seed, even from foliage cultivars, will vary considerably, from ones indistinguishable from moorland plants to perhaps a new find unlike any available commercially. However, there is more chance of winning the lottery than obtaining a truly different plant!
Propagation from seed is often used where heather is needed for restoration work or for such areas as golf courses. Heather seed can be triggered by fire and light, so germination is increased if the seed is heated to 120ºC for 30 seconds before sowing in the propagation compost. Recently it has been discovered that in addition to the more obvious effect of heat, the smoke from fires is responsible for stimulating the germination of seed of many Erica species in South Africa. It is thought that this effect would hold true for hardy heather species as well.
1. Seed is sown in conventional plastic trays and is covered by a thin layer of soil.
2. The trays are placed in a polythene tent and smoke is pumped into the tent by means of a plastic pipe from a large metal drum.
3. The smoke is generated in the drum by burning a mixture of dry and green leaf and stem material which should resemble as closely as possible the vegetation found on heathland.
4. The trays are left in the smoke for 1 to 2 hours.
5. The seed trays are then placed under cover in the shade until the seeds have germinated. Germination can take as long as six months.
6. The best time to sow and treat seed is in the late sumnmer and early autumn when day /night temperature fluctuations are at their maximum.
It is now possible to obtain a primer solution containing a combination of natural substances which have been found to overcome dormancy and stimulate seed germination. It takes the form of an impregnated paper disc which can be obtained from Kirstenbosch National Botanical Garden, Claremont 7735, South Africa.
1. Place a primed paper disc in a cup. Add 50ml of water and wash the primer from the paper.
2. Seed is sown in conventional plastic trays and covered with a thin layer of soil.
3. Add 950ml of water to the primer.
4. Water seed trays carefully with primer solution using a fine hand spray.
5. Keep wet with solution for at least 24 hours. Water thereafter as normal.
This is the simplest and most reliable method for the gardener who wants just a few plants of a particular variety.
1. Select a branch or number of branches on the outside of the plant.
2. Make a shallow trench with a trowel into which the selected branch can be drawn.
3. Fill the trench with a mixture of sphagnum moss peat and grit sand.
4. Draw the selected branch down into the trench, taking care not to break it.
5. Peg it down firmly with a wire hook about 15cm (6 in) long, making sure that the tip of the branch is turned upwards.
6. Cover the branch with the peat/sand mixture and mound up around the now upright tip.
7. Water well.
A layer can be made at any time of year. Nine to ten months later a root system will have formed at the bend in the stem where it was pegged, and the new plantlet can then be severed from its parent and planted in its final growing position. Several such layers can be made around the plant without affecting its appearance.
A development of this technique is to dig the plant up, make the hole considerably deeper and re-plant so that only the growing tips show above the soil. These will produce new roots and can be severed from the old plant after about 6 months.
The most common method of producing heathers is from cuttings. Many gardeners have trouble rooting heathers from cuttings but if a number of simple rules are followed, a high success rate can be achieved.
Choice and preparation of cutting material – species by species
What happens when a cutting roots? Why do some species root easier than others? Why do cuttings root easier at certain times of the year? These questions and many others like them arise irrespective of what form of propagation is used.
Rooting depends upon many inter-related factors, some beyond our control, but other aspects are helpful in determining the type of material we should select. In general, cuttings should be taken from healthy, vigorous plants, preferably not more than three years old, but other aspects are more species-dependent. There is no need to use rooting hormones for hardy heathers.
Calluna vulgaris cuttings can be taken in April using the leafy growth appearing above last year’s flowers. In this case, select stems where the leafy growth is at least 1cm long. Cut the stem with a sharp knife 2cm below the leafy growth. Remove any dead flowers by rubbing your finger and thumb down the stem.
Preparation of Calluna vulgaris cuttings in April
Calluna vulgaris cuttings can also be taken during July and August from the growth just below the flowering stem. Select stems which are firm and just turning straw brown. Discard stems where the leaf nodes are more than 2mm apart as these will be more difficult to root and make a less shapely plant. Cut the stem with a sharp knife immediately below the flowers and then cut again to create a cutting 4 to 5cm long. Remove the leaves from the lower 2cm of the cutting by rubbing your finger and thumb down the stem.
Preparation of Calluna vulgaris cuttings in July
Daboecia cantabrica and Daboecia x scotica cuttings are best taken in July. Select side shoots which are firm and just turning to straw brown about 4 to 5cm long. Pull down carefully to tear the cutting from the main stem so as to leave a small ‘heel’ at the base of the cutting. Remove the leaves from the lower half of the cutting by pulling downwards. Sometimes this type of cutting is not readily available, in which case prepare in a similar way to a July Calluna cutting.
Erica carnea cuttings are best taken in July or August by selecting stems which do not have buds forming on them. Ideally heel cuttings about 4 to 5cm long are best but if in short supply a tip cutting can be prepared but cut off the top 5cm of growth with a sharp knife. Avoid stems where the leaf nodes are more than 2mm apart. The lower half of the leaves should be removed by rubbing a finger and thumb downwards along the stem.
In the case of the heel cutting, nip out the growing tip. As Erica carnea flowers profusely, it may be difficult to find cutting material without buds, in which case these will have to be used. Prepare as above but remove all flower buds by rubbing a finger and thumb upwards along the stem.
Erica carnea cuttings can also be taken in March and April. At this time of year use the top 5cm of growth but do not pinch out the growing tip. Nature has already provided a number of embryo shoots, more in fact than you can create by pinching out the tip.
Preparation of Erica carnea cuttings
About two weeks after the cuttings are taken, a gradual swelling of the whole stem is observed. After three to four weeks roots always start to form above a leaf nodule. After about ten weeks, more roots can be observed coming through the callus formed over the nodules. These tend to be rather weak compared to the other roots which are well developed by this time.
Erica cinerea cuttings are best taken during July and August, using non-flowering heel cuttings. If available, these are likely to be quite small, 1 to 2cm long. Remove the leaves from the lower half of the cutting by rubbing finger and thumb down the stem. Often heel cuttings of this type are difficult to find, in which case the stems below flowering shoots can be used, provided the spacing between the tufts of leaves does not exceed 2mm.
Cut these from the plant in a similar way to that described for July Calluna cuttings, but as roots usually only appear from the base of the cutting, make sure the lower cut is made immediately below a tuft of leaves. Remove the leaves from the lower half of the cutting.
Preparation of Erica cinerea cuttings
This species roots by producing a large swelling at the base of the cutting (it does not seem to matter whether it is a tip or heel cutting). The time it takes to do this varies considerably. Roots appear two to three weeks later. It only rarely roots around nodules, which may account for the increased difficulty most propagators have with this species.
Erica ciliaris, Erica mackayana and Erica tetralix
These species root in a similar manner to Erica cinerea.
Erica ciliaris, Erica mackayana and Erica tetralix cuttings are best taken during July and August using non-flowering heel cuttings about 1 to 2cm long, which are usually plentiful. Remove the leaves from the lower half of the cutting as described above.
Erica x darleyensis, Erica erigena and Erica vagans
These species root in a similar way to Erica carnea. Interestingly, Erica x williamsii behaves in a similar manner to Erica tetralix despite the leaf attachment being closer to Erica vagans.
Erica x darleyensis, Erica erigena and Erica vagans cuttings are best taken in August, making particularly sure in the case of Erica erigena that the stem is semi-ripe, i.e. firm and turning to straw brown. Take and prepare heel cuttings 3 to 5cm long as described for Erica ciliaris.
Methods of propagation
Once a cutting has been severed from the parent plant, it will continue to loose moisture via the leaves until such time as it produces roots. The two basic ways of rooting heather cuttings attempt to keep this transpiration loss to a minimum. The first, open to all amateur growers and described below, relies on keeping the cuttings humid, the second is more sophisticated; mist propagation.
“Close polythene” method
This method relies on keeping cuttings humid to minimise transpiration and is suitable for rooting most of the widely grown hardy species of heather. There are many adaptations of this method, depending on whether small or large quantities of rooted cuttings are being produced.
The main danger with this approach is the risk of fungal attack. If small numbers are required, the following method minimises that risk
1. Place some sand into a 100mm (4″) clay pot.
2. Place a small amount of compost at the base of a 150mm (6″) plastic pot.
3. Place the clay pot inside the plastic pot and lightly firm more compost in the ring between the two pots.
4. Dib holes with a nail about 2cm apart close to both edges.
5. Place the cuttings in the prepared holes but do not firm them in.
6. Once the pot has been filled, water heavily so that compost seals the holes.
7. Leave for 20 minutes and seal the plastic pot in a polythene bag (one with no holes in it), ensuring that the polythene is kept clear of the cuttings.
8. Place the pot against a north wall or in light shade under a bush or a place where the sun cannot play on the polythene bag. NEVER PLACE THE POT IN A GREENHOUSE as the temperature variation is too great, nor in a propagator unless you are prepared to spray the cuttings five or six times a day.
9. Leave for several months, checking occasionally that the polythene bag is fogged. If not, heavily water the sand in the centre pot, and re-seal. Any cuttings that die should be removed to minimise disease.
10. To check that rooting is taking place, lightly pull the cutting. If resistance is felt, you can be sure that rooting is taking place. Those not rooting will come out easily and can be replaced just as easily.
If slightly larger numbers required, the twin pot approach can be replaced by a plastic seed tray. Lightly firm compost into the tray and dib holes 2cm apart. Follow steps 5 to 8 above.
Leave for several months, checking occasionally that the polythene bag is fogged. If not, simply heavily water again, leave 20 minutes and re-seal. Any cuttings that die should be removed to minimise disease.
This method is slightly more prone to fungal attack and therefore is most effective if propagation is delayed until September.
Many large heather producers use this approach on a commercial scale, placing plug trays on heated beds with shallow sides. Polythene sheet is stretched across the bed and is turned every 3 or 4 days to minimise fungal attack. The cuttings are routinely sprayed with a non-systemic imidazole fungicide.
Care has to be taken to wean the cuttings from the humid atmosphere once rooted. On dull days, the polythene cover should be lifted slightly for an hour to start with, gradually increasing the period until the cover can be completely removed.
The rooted cuttings can either be potted on or planted out in a nursery bed.
Transplanting is best done in early spring, but if the cuttings are sufficiently well rooted by September, they can be potted on and over-wintered in a cold-frame.
Knock the cuttings out of the seed tray in a similar manner as one would a plant from a pot. Divide the cuttings from each other using an old knife.
Place the relatively dry compost into a 9cm pot (smaller sizes are more prone to drying out) and lightly firm. Make a hole in the centre of the pot and plant the cuttings deeply, burying any bare stems so that the lower foliage rests on the soil surface. Make sure that the cuttings have been firmed in well. Water heavily and place the pots outside in a well drained, not too exposed area.
If the nursery bed approach is adopted, prepare the ground well, removing all weeds and adding sufficient grit, acid sand and sphagnum moss peat to create a fine tilth. A dressing of general fertiliser such as John Innes base at 55 grams per square metre will help to produce strong healthy plants.
Water regularly throughout the spring and summer. Rapid growth will be made, so, to ensure a shapely plant, prune all Erica carnea back to 3cm to 5 cm at least once during the growing on period.
For most cultivars, rooted cuttings transplanted in spring should be ready to be planted out in their final positions by the following autumn but some Erica carnea cultivars may need another growing season.
Use a proprietary ericaceous compost mixed 2:1 with horticultural perlite. The important feature to look for when purchasing compost is to ensure that it is suitable for ericaceous plants.
Alternatively, the compost made up for propagation of cuttings can be used (this time there is no need to sieve the peat). If this approach is taken, a weekly supplementary feed will be required using a proprietary liquid tomato fertilizer.
With peat becoming a diminishing resource, a considerable amount of research is being conducted to find an alternative to peat. Peat-based composts have been optimized over a number of years and a complex science has developed describing how nutrient and water holding capacity are determined in such media. Several alternatives are being pursued and no doubt more will be investigated, but at present, composts based on coconut fibre or wood fibre are unsatisfactory.
By careful planning, a new heather garden can give a colourful display in 3 to 4 years, which will require little maintenance and will last 15 to 25 years. Heathers are best planted in beds totally devoted to themselves, except for the addition of a few conifers to provide contrast in height and form.
The first decision that has to be made is whether to have a heather bed designed to peak at a particular time of year or whether to have a bed which has something in flower for most of the year. The “peaked” bed will give a spectacular display for 6 to 10 weeks and then by judicious use of foliage varieties will give a subdued but still colourful display for the rest of the year. If space permits, using several beds peaked for different seasons overcomes any doubts about this approach.
Alternatively, “all-year-round” beds give a near continual display without ever being spectacular and have the advantage where only a few heathers can be grown.
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. 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.
Heathers benefit from an annual pruning and the following schedule may be of assistance.
Each February or March, prune long flowering spikes back to plant. Trim off all flower heads.
Each February or March, trim off dead flowers and seed pods, to make bushy growth.
Every other April or May, trim flower heads with shears. Trim the more vigorous cultivars hard to stop the centre going bare.
Each April or May, trim off dead flowers.
Each February or March, trim off dead flowers particularly long flowering spikes.
Erica tetralix, Erica x stuartii
Each April or May, trim off dead flowers.
Erica arborea, Erica australis, Erica erigena, Erica scoparia, Erica terminalis, Erica x veitchii
After flowering, trim half of previous year’s growth for the first four years to encourage bushy growth; trim off broken branches. Stake for support.
Erica x darleyensis, Erica x oldenburgensis
Trim each June. Do not be afraid of limiting growth.
Erica manipuliflora, Erica x griffithsii, Erica multiflora, Erica vagans
Leave flower heads on for russet colours during winter. Trim every March. Do not be afraid of limiting growth.
Each February or March, trim off dead flowers.
Erica x watsonii, Erica x williamsii
Trim hard, every other year in March.
In general, trimming retards the flowering by two to three weeks.
A heather garden should be planted in a position where it will be unshaded for all or most of the day and, if possible, facing south. Planting on dry sites or under trees should be avoided. Bold plantings of groups of 5 or more of each cultivar give a good overall effect, but single cultivars, chosen to contrast or complement each other can look attractive in a small garden.
Where possible beds should be of informal shape with no straight edges. Plan on using 5 plants per square metre (4 plants per sq. yard) making allowances for other small leaved shrubs planted with the heathers.
Plant deeply with the lower foliage resting on the soil surface.
It is safer to assume that Cape heaths must not receive a frost, although certain species are known to survive about 5 degrees Celsius of frost. As a result they are best regarded as a cool greenhouse plant, although they can be grown indoors under certain conditions. They are invariably grown in pots.
Despite enduring long hot and dry summers in South Africa most cultivated heathers hate being dry and this is the greatest danger. So keep pots or planters on a bed of pebbles which are kept wet at all times. Water the foliage from time to time as well, particularly in summer. Heathers rarely show sign of wilting so it is already too late if significant leaf drop occurs.
If heathers are kept indoors, they require a cool and well-lit moist atmosphere. The best places are usually a kitchen, bathroom, conservatory or even a sheltered porch.
When purchased most plants will be already pot-bound. Knock the plant out of its present pot, if the roots are brown (rather than white) then it needs potting on in a lime-free compost. Tear open the base of the root-ball as this will encourage new root growth. Repeat this operation annually. The earlier this is done after purchase, the greater the chance of survival.??Prune immediately after the flowers have faded by simply trimming off the dead flowers. They should not be pruned too hard i.e. into old wood as most heathers will not sprout new foliage from old wood.
Place the pots outside when risk of severe frosts has passed, keeping them WELL IRRIGATED DAILY. Feed with a liquid tomato fertiliser as directed by the manufacturer. Provide protection once again when severe frosts are likely.
Most Cape heaths form tall shrubs and it is advisable to prune strong leading shoots for the first year to produce a compact plant. However, the plant usually flowers on these long spikes and, therefore, a choice has to be made between flowers and the shape of the plant in the early years.
text to come