Gardening in Dorchester: Caring for azaleas after they’ve flowered

By Laetitia Sands, Special to Dorchester Banner
Posted 5/12/22

Do your azaleas look particularly gorgeous this spring? I imagine it has something to do with the inordinate amount of rain we've had in the past few months.

Azaleas like constant moisture, but …

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Gardening in Dorchester: Caring for azaleas after they’ve flowered


Do your azaleas look particularly gorgeous this spring? I imagine it has something to do with the inordinate amount of rain we've had in the past few months.

Azaleas like constant moisture, but well-drained, acidic, humusy soil and filtered sunlight, if possible. I read a description of the shrub which called it “a lazy gardener's dream plant, if only... (the gardener) will cooperate with nature.”

Insects and disease rarely do serious damage to a healthy azalea. Any ailments it may have stem mainly from poor nutrition or the wrong location. And the plant doesn't need regular pruning, apart from occasionally removing dead, puny or overgrown branches. But if you want to prune your azaleas to keep them well-shaped, vigorous and full of flowers, the time to do it is just after they've flowered, meaning quite soon.

Most flowering shrubs should be pruned, if at all, right after they've flowered. In the case of azaleas, most of which are broadleaf evergreens, pinch or cut back the end buds of the new sprouts to get a bushier, more flower-filled shrub. Doing so will force the so-called latent buds along the sides of the branches to develop.

But take care not to trim off the large buds that will develop into flowers next year. And, whatever happens, don't pinch them back after early August or you may damage the growing flower buds and cause winter injury to the tender new shoots.

On the other hand, if you want to renovate an overgrown, leggy azalea completely, which involves more drastic pruning – even cutting it to the ground – do it next year, in early spring, while the plant is still dormant. An important point: If you prune an azalea severely, do not fertilize or water it until the new growth is well established.

Looking ahead to summer, you can create new azalea plants then, or in early spring, either from softwood cuttings of young growth or by layering. With inflation boosting the price of so many things, you can save quite a bit of money by propagating your own plants. It will take four to six years before they flower, however, and the blossom may not be identical to the original azalea's.

Another thing to do in summer, specifically late June or July: Mulch your azaleas with an inch or so of compost, which will give them nitrogen and other nutrients they need to grow well. Do it every summer. But don't mulch them with bark, which contains almost no nutrients.

Do your azaleas look bereft of leaves in fall, except at the very top of their branches? Do some, or many, of the leaves turn yellow and red? This is not normal fall coloring. It means either the soil is not acidic enough or the plants need food, particularly nitrogen.

Azaleas do not stop growing in fall and winter until the temperature drops below freezing. If their leaves drop or change color, they're likely starving because they've sent whatever nutrients they can get up to the flower buds that are forming at the tips of the branches.

If you prefer to give them fertilizer, rather than compost, wait until after the first frost of winter, then apply it under the drip line of the plants. This will stimulate better growth in the spring.

The late horticulturalist Dr. Francis Gouin, in his book “Enough Said!” advised using a 50% organic fertilizer such as 10-6-4 or ammonium sulfate, applied at a ratio of one cup for every three feet of an azalea's height and spread. If you use ammonium nitrate or urea, the ratio should be one-third to half a cup for every three feet, and if urea form or uramite, half a cup. 

If you have bark mulch around your azaleas, make sure to water the plants well after fertilizing them. And never dig in the fertilizer because azaleas have shallow roots and cultivation will damage them.

By the way, never fertilize azaleas more than once a year. Over-feed them or fertilize them too late in winter, and they won't tolerate the cold well.   

Do your azaleas produce too few flowers? This may result from the plants getting baked by the summer sun. I remember the horror of seeing the leaves of my two beloved azaleas droop dramatically in mid-summer. The only answer seemed to be watering them every morning, before the day heated up.

Azaleas need some sunshine to bloom well, but the direct summer sun can hurt them. Where azaleas really thrive is at the edge of woods, where they get filtered sunlight, or in some other sheltered spot where they get only partial sun.

Their buds, which form in summer and fall for the following spring, need lots of moisture to grow as they should. The whole plant will wilt quickly, if not kept moist. Even after one such experience, they're slow to recover. As a result, mulching is extremely important, especially in summer and preferably with organic materials such as pine needles, oak leaves and decayed sawdust from oak, cypress, hemlock or a mix of all three.

Put a layer of this natural mulch at least four inches deep around your azaleas. It will keep the roots moist in summer and protect them from the cold in winter. Also, it will reduce the number of weeds and provide a home for lizards and frogs, who eat undesirable (to the gardener) insects.  

An azalea's roots are very shallow. Most lie within three to four inches of the surface, so they need to be protected from the heat of summer and the frigid temperatures of winter. A mixture of pine needles and oak leaves work particularly well. The needles, laid on top of the leaves, should prevent the leaves from blowing away. Pine needles are high in acidity and slow to decay, while oak leaves break down more quickly and have more food value, but less acidity. 

Adding seaweed to the mulch will furnish trace minerals. But never use manure because of its alkaline reaction.

Now, what is it I read about azaleas being “a lazy gardener's dream plant?” In the meantime, happy gardening!

Laetitia Sands is a master gardener in Dorchester County.