Azalea mollis - Azalea molle - are a wide ranging group of deciduous azaleas that originated from Belgian and Dutch sources, being hybrids between the Azalea molle and A. m subsp. japonicum.
Thereafter there have been many other hybridizations - notably the English hybrids as typified by the Knap Hill hybrids and also the Exbury hybrid deciduous azaleas. Ghent hybrids will also fall into this group.
We make no apologies for listing these as Azaleas - rather than the botanically correct Rhododendrons - for they are universally known amongst gardeners as Azaleas.
These deciduous Azaleas have complex hybrid ancestry. Ghent Hybrids - were bred in Belgium for which we give thanks. Further hybridization was carried out at Knap Hill, and those are naturally classified as Knap Hill or Exbury Hybrids.
In my close encounters of both types, I have always found the Knap Hill or Exbury hybrids to have the better scent - especially in the yellows and lighter colours.
All of the images on this page are from deciduous Azaleas raised from a single packet of Azalea Knap Hill/Exbury hybrids many years ago, at Great Comp Garden in Kent UK. Many of the Knap Hill hybrids have gorgeous scent, unlike the true Azalea mollis, which seem to have no or little fragrance. That from the experience of being up close to take photographs!
The image on the left shows the wide range of autumn foliage colour that is to be seen on mass plantings of the deciduous Azalea. So we get two good seasons of colour - early summer for the flowers and autumn for the foliage.
The flowers are typically funnel shaped, and long lasting. The lighter coloured flowers seem to generally have the best scent - especially the yellows. As well as having a huge range of flower colours, Azalea mollis hybrids have a fantastic range of autumn - Fall - colours as the leaves prepare for winter. ( All the above Azaleas were growing on the edge of woodland paths, with access to good light and sunshine.)
Like all members of the Azalea family, Azalea mollis are best grown in acid soils. Either naturally humus rich soils, such as would be the case in semi woodland situations or with an added organic mulch every autumn. They are not happy in waterlogged conditions, and fare best if in well drained soil.
Deciduous Azaleas are tolerant of semi shaded positions, but are at their best if planted in full sun. This probably allows the wood to ripen for producing the best flowering display for the following spring season.
Frosts are not so damaging to Azalea mollis types as with the evergreen azaleas. This is largely due to the fact that they are later flowering - normally May or even June. Thus the opening buds are not normally affected by late frosts. Togther with that, this group is fully hardy for garden use.
Container Growing This group of Azaleas are well suited to being grown in patio pot situations. Keep the pot shaded from the hottest of suns, and give sheltered situation in severe winter to avoid the possibility of the pot compost freezing.
Azalea mollis varieties can easily reach 8ft (2.4m height). Advice on Pruning Azaleas The most important thing being the dead-heading of the faded flowers to allow for good growth of next season's flower buds. It takes a lot of plant energy to set seed, so the dead heading will help to maintain a healthy and vigorous plant.
Seed Propagation Azalea mollis and related hybrids readily set seed which should be collected as soon as ripe - just before the seed pod open/burst. The seed con be sown on the surface of a peat compost - or just peat will a little sand added - as soon as the seed is collected. If you have a solitary plant, then there is a reasonable chance that the new seedlings will resemble the parent. In practice, there will be many different forms as to flower and growth habit.
Cuttings of Deciduous Azaleas are best done with semi ripe cuttings in mid summer. Whilst they are relatively easy to root, they will need cold house or cold frame protection through the first winter - potting them up in early spring. Alternatively these Azaleas can be propagated from layers - either by pegging a supple low growth onto the ground, or by air layers.
Insect Pests Azalea molle types are relatively trouble free as far as insect pests are concerned, though you might find signs of vine weevil damage on the foliage. Container grown plants might fail if there are vine weevil larvae in the compost. Whitefly is sometimes (rarely) a minor problem.
Diseases include Honey Fungus (rarely) Powdery Mildew on the foliage which can severely affect the flowering capabilities for the following spring, and sometimes rust on the leaves. The latter is rarely a problem of any magnitude.
In open ground situations, with regular mulches, the only feed normally required would be a dressing of bonemeal in early spring - or blood fish and bone. Osmocote could be the alternative for a slow release fertiliser throughout the growing season. Osmocote would be the preferred choice for container grown plants.
This is usually a sign of lime in the soil - it only needs to be slightly alkaline to bring about this chlorosis. An annual dressing of iron based feed/treatment will usually do the trick. It may be that if the azalea is growing in pot container, the tap water used for watering may be from a limestone area!
By David Hughes