Azalea

Azaleas are in the genus rhododendron, with evergreen azaleas in the subgenus tsutsusi and deciduous azaleas in the subgenus pentanthera.

The difference between azaleas and rhododendrons is in their leaves;

Azalea leaves tend to have long straight hairs parallel to the leaf surface, and along the midrib on the underside of the leaf.

They also tend to be thinner, softer, and more pointed than rhododendron leaves.

Another (but less reliable) distinguishing characteristic is in the number of stamens, i.e. most azaleas have 5 or 6 stamens, whereas most rhododendrons have 10 stamens.

These deciduous or evergreen shrubs flower in a multitude of colours.

They prefer an ericaceous (acid) soil meaning in areas of alkaline soil it is better to grow these plants in containers filled with ericaceous soil.

If planted in the border they require humus rich free draining soil.

Generally they only require sufficient pruning to keep the plants confined to a given area and shape.

If pruning is required, it should be done before mid-summer to allow the plant to produce the flower buds for the following year.

To do it later will result in fewer flowers the following year.

Container culture:

As with outdoor varieties, flowers are generally produced in May, although some variations may occur.

They will not tolerate chalky or limy soil; therefore they must be grown in ericaceous compost.

Week 1>: Avoid dryness at the roots by keeping the plants well watered.

Allowing them to dry out will lead to sudden leaf-drop so keep compost permanently moist.

Check this regularly, or stand the pot on damp gravel.

Alternatively: you can keep the root ball moist by dunking the whole pot in a bucket of water.

How often you do this will depend on how quickly the compost is drying.

Keep pots in a bright but cool position away from radiators and fires.

Week 8: Sow seeds thinly in pots/trays of moist, finely sifted horticultural peat.

Cover seed with a sprinkling of silver sand or fine vermiculite, and cover the pot/tray with a piece of glass until they germinate, and maintain a minimum temperature of 16°C (60°F)

Place the pots/trays in a heated propagator and cover them with glass.

Alternatively in Week 15, sow them in a cold frame or unheated greenhouse.

Keep the seedlings well shaded and the compost surface moist.

Prick out when they make their first two true leaves 25-50mm (1"-2") apart in boxes /trays or 75mm (3") pots of ericaceous compost.

Protect the seedlings from strong sun and keep the compost moist but not soggy.

Week 21: (The following year) plant out the seedlings into a coldframe or nursery bed.

Week 26: Take 50-75mm (2"-3") long semi-hardwood cuttings and insert them in boxes/trays of equal parts (by volume) peat and river sand.

Place pots/trays on a hot bed and maintain a soil temperature of 16°C (60°F)

Mist spray cuttings regularly to prevent dehydration prior to rooting.

When rooted, pot the cuttings up into 75mm (3") pots of ericaceous compost.

Grow on potted on cuttings in a cold frame or cool greenhouse until the following April.

Week 26: Plunge the plants in an outdoor bed or place in a sheltered spot until September.

If possible use soft water (rainwater) for both watering and spraying.

Week 40: Pot up Indian Azalea (rhododendron simsii) plants in 250mm (10") pots filled with ericaceous (lime free) compost.

You can make up your own ericaceous compost by mixing, three parts (by volume) moss peat, one part sharp lime-free sand or perlite, and add Chempak ericaceous base mix as per the instructions on the packaging.

Alternatively use equal measures (by volume) of fibrous loam, leaf-mould, moss peat, and river sand.

Before re-potting check that the root ball is moist, if not, immerse in water to soak.

Trim back dead or straggly shoots then carefully tease away some of the old compost, from the outside of the root ball.

Re-pot the root ball into a clean pot of similar or slightly larger dimensions.

Grow on in a cool, but frost free place.

Week 50: Fetch pots in to a warmer environment and maintain a minimum temperature of 16°C (60°F) until the blooms open.

Control the humidity around the plant/s by spraying them from above.

This should be done at least once per day until the flower buds show colour.

Outdoor cultivation:

Azalea need a position sheltered from cold winds and early morning sun.

They grow to around 900-1200mm high with a similar spread.

Flowers are produced in May.

They will not tolerate chalky or limy soil, the ideal is a sheltered, semi-shaded positions with well-drained sandy loam.

Other types of soil should be enriched with liberal amounts of farmyard manure, peat, or leaf-mould prior to planting out.

Avoid dryness at the roots by keeping the plant/s well watered and mulched.

Generally the large leafed varieties require more shade than the small leafed varieties.

Varieties that flower prior to May require protection from early morning sunshine, to avoid damage to flower buds caused by rapid thawing after frost.

Culture notes:

Week 8: Sow seeds thinly in pots/trays of moist, finely sifted horticultural peat.

Cover the seed with a sprinkling of silver sand or fine vermiculite and cover the pot/tray with a piece of glass until they germinate, and maintain a minimum temperature of 16°C (60°F)

Alternatively, sow week 15 in a cold frame or unheated greenhouse.

Keep the seedlings well shaded and the compost surface moist.

Prick out when they make their first two true leaves 25-50mm (1"-2") apart in boxes /trays or 75mm (3") pots of ericaceous compost.

Protect the seedlings from strong sun and keep the compost moist but not soggy.

Week 15: Apply 100-150 gm (4-6oz) of balanced fertiliser per square metre over an area equal to the spread of the plant.

Alternatively use with a solution of iron sequestrene.

Week 20: Layering can be done at any time of the year, but now is as good a time as any now that the soil is warming up.

Select young stems that are low enough to bend down to ground level.

Cut a small lengthways slit on the underside of the selected stem, anchor the stem down with a 'U' piece of wire and cover the section with 50mm (2") of ericaceous compost.

Keep the end of the stem vertical by attaching it to a short cane.

Allow a couple of years for the layer to root before severing it from the parent plant.

Week 21: (The following year) plant out the seedlings into a coldframe or nursery bed.

Circa Week 23: the leaves on evergreen azalea may start swelling and distorting, and turning from their usual deep green to a pale, washed-out colour this is a sign that the plant/s have been affected by azalea gall.

This is a fungal disease so pick off the swollen leaves to prevent the spores spreading, and spray with a fungicide.

Week 24: Take 50-75mm (2"-3") long semi ripe cuttings and insert them in boxes/trays of equal parts (by volume) peat and river sand.

Place pots/trays on a hot bed and maintain a soil temperature of 16°C (60°F)

Mist spray cuttings regularly to prevent dehydration prior to rooting.

When rooted, pot the cuttings into 75mm (3") pots of ericaceous compost.

Grow on potted up cuttings in a coldframe or cool greenhouse until the following April.

Week 36: If required, transplant established plants to new locations.

Prepare the ground as mentioned above, and plant them in firmly with the top of the root-ball level with, or slightly below, the surface of the new b

It is advisable to mulch with peat or leaf-mould after planting.





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