The most important thing to realise about all types of azaleas is that they are members of the Ericaceous group of plants, which means that the soil for azaleas needs to be an acidic soil. Azaleas do not grow well – if at all - in lime soils. A ph level of 6 or below is what you will be aiming for if you want to grow healthy azaleas.
Azaleas are many and varied, but the growing conditions for all – except the houseplant types (Azalea indica) – are the same. Whether you have evergreen or deciduous azaleas, follow these general guidelines.
They can be planted as isolated specimen shrubs; grown for groundcover; in semi woodland conditions; open aspect as long as they are not subject to harsh midday sun. Once planted and established, azaleas require very little attention and will give years of pleasure – growing slowly and rarely outgrowing or outstaying their original position.
The planting position is important as with other shrubs, though being slow growing there is scope to move other plants out of the way if they crowd in on the space allotted to your azalea plants. A semi shaded position is by far the best situation, though dappled shade – especially at midday sun time is another possibility.
Avoid heavy frost areas, or be prepared to bemoan the spoiled flowers resulting from frost damage to the developing buds in late winter.
Overhead cover from deciduous trees and shrubs normally goes a long way to abate this problem. You will soon notice if they have suffered from the frost, as the buds will start to lose their firmness and eventually turn brown concluding in the loss of flowers.
If planted in an area prone to frost, damage can be prevented with a covering of horticultural fleece. This is preventative and of no use once the damage has been done.
Azaleas and their big-brother counterparts the rhododendrons are generally surface rooting with main feeding roots just below the soil surface. It is important not to plant your new azalea too deep. If possible, no deeper than the existing soil surface of the pot.
Plant azaleas in early spring; just before the new growth starts begins. Avoid planting in winter, though mid autumn can be an option in areas where there is adequate shelter from drying or unsettling wind. Deciduous Azaleas may be planted in Fall, but evergreen azaleas in spring at bud stage - or after flowering, which will be late spring.
Don’t dig the planting hole to deep, or subsequent settling of the soil will mean that the root ball could possibly sink lower into the ground with accumulating debris and leaf litter or mulches covering to roots too deep.
Young pot-grown azaleas will often have a shrub canopy much larger than is normal for the root area. Find a different means of support than simply planting a bit deeper to help stabilize things. A thin stake driven down through the root ball, but not to near as to damage the main roots near the stem would be the best option. The top of the stake can be cut off level with the foliage canopy.
All ericaceous plant – of which the azaleas and rhododendrons are – will need an acid soil – under a ph level of ph 6. Azaleas can be grown for a short time in neutral ph level soil – with the help of an applied dressing of chelated iron – normally sold as ‘Sequestrene’. This effectively counters the problem of locked-up iron in the soil.
Raised peat or acid soil beds are a possibility for a while, but eventually, existing soil water will be drawn up into the beds. If the soil water contains lime, this will affect the health of the azalea plants.
The same is true about the advice given about plunging potted azaleas into the ground. There will inevitable be drainage holes in the container, and this will allow the existing soil water to percolate into the pot.
Provide plenty of peat or other organic material in the planting hole, with a dressing of bonemeal. Do not use any chemical fertiliser during planting in order to prevent scorching the fine delicate root system.
Firm the plant into the ground but not to the extent of ramming your boots around the root zone. Water well after pruning and that will help to settle the soil around the roots.
Azaleas can be grown in all manner of containers, and make a splendid temporary floral display near the house on a patio or deck. They can also be taken indoors in alight airy room for a short time, normally no longer than a week. (We are talking now of outdoor azaleas and not the florist’s indoor Azalea indica types.) All of the above information is pertinent with additions.
It is possible to by special ericaceous compost in which to pot your azalea. These are normally peat based and will retain their acidic properties for many years – providing that any watering is done with a non-lime water. Rain water is normally best, but tap water is acceptable if from a non-lime area.
If the leaved gradually turn light green through to yellow it will either be lack of food – or probably lime in the water.
Azaleas and rhododendrons have fine fibrous root systems with the feeding roots normally at or just below soil surface level. These are prone to damage if fed with chemical fertliisers. Bonemeal, Fish Blood and Bone (sparingly) are the best of the fertilisers for this use, but it is also possible to use slow release fertilisers such as Osmocote. Reduce the dose by half for any proprietary fertiliser – if necessary feeding in small doses during the growing period after the flowering has finished.
Providing your Azaleas are grown in an acid soil, well shaded, and away from frost pockets, there are not too many problems when growing Azalea bushes. If the cultural aspects are taken into account and heeded, you should have relatively trouble free pleasure.