Garden Azalea

Deer are the largest garden problem across much of the country, and where pressure is high they set the limit on what you can grow at all. They browse at night and around dawn and dusk, taking tender shoots, leaves, buds, flowers, and fruit within about five feet of the ground, and they come back night after night to anything they have found and liked. Because they have no upper incisors they tear rather than cut, leaving ragged stem ends - that is how you tell deer damage from a rabbit's clean angled cut. In fall, bucks rub their antlers on young trunks and can strip the bark right around a stem, which kills a young tree outright. Palatability varies enormously between plants and between seasons: a herd short of food in late winter eats things it ignores in June, and no plant is truly deer-proof.

Watch for: Growth cleanly missing overnight, with the plant browsed back to a level line about as high as a deer can comfortably reach. Ragged, torn stem ends rather than the clean angled cut a rabbit leaves - the single most reliable identifier. Buds and flowers gone while the foliage below is untouched, since deer often take the best part first. Hoof prints and droppings in soft ground near the damage. Repeat visits, with fresh damage each morning once a planting has been found. On young trees, shredded and stripped bark and broken low branches in autumn - that is antler rubbing rather than feeding.

Prevent: Fencing is the only thing that reliably works. Eight feet is the standard for excluding deer, or two parallel four-foot fences a few feet apart, which they will not jump because they cannot judge the landing. Short of that, cage individual plants: a sturdy wire cage or trunk guard around every young tree, left on until the trunk is thick and the canopy is above browse height, prevents both browsing and antler rubbing and is the single highest-value thing you can do for a young tree. Repellent sprays do help at moderate pressure, but they wash off and deer habituate, so reapply after rain and rotate between different types through the season. Motion-activated sprinklers, scent deterrents, and noise devices work for a while and then stop. Siting matters too: plants close to the house, in daily traffic, and screened behind other planting get browsed less than the same plant out at the boundary.

Treat: There is no chemical fix, only exclusion and recovery. Get physical protection up immediately after the first damage, because deer return to a known meal, and reinforce or rotate whatever you were relying on before. Most plants regrow from browsing if the crown and roots are intact - feed and water a grazed plant and protect the regrowth while it comes back. What does not recover in the same season is anything whose buds or flowers have been taken, and a young tree whose bark has been rubbed right around the trunk is usually lost. Where deer pressure is genuinely heavy, the honest answer is to fence properly or to grow the plants deer leave alone, rather than to keep replacing losses.

Do not count on the grayanotoxins to protect it - evergreen azaleas are among the most heavily browsed shrubs in suburbia, and a hungry herd in late winter will strip a foundation planting of leaves and flower buds in a night. Fence, cage, or rotate repellents from autumn onward, not in spring when the buds are already gone.

Root rot is not one organism but a group of soil fungi and water molds - Pythium, Phytophthora, Fusarium, Rhizoctonia and others - that sit harmlessly in most soils and only turn destructive when the ground stays saturated. Waterlogged soil drives the air out, the roots suffocate, and the weakened tissue is invaded and goes soft, brown, and stringy. Because the damage is underground you usually see it first as something that looks like drought: wilting, yellowing, stunting, a plant that does not respond to being watered. Overwatering, heavy compacted ground, a low spot that collects runoff, a pot with no drainage or a saucer left standing full, and cold wet soil in winter are the usual causes. Once roots have actually rotted there is no cure - this is a problem you prevent rather than treat.

Watch for: Wilting in the middle of the day on a plant whose soil is damp - the classic tell, and the reason people water a rotting plant and finish it off. Leaves yellowing from the bottom up, dull off-color foliage, and growth that stalls for no visible reason. Whole shoots, or one side of the plant, collapsing while the rest still looks fine. Soft, dark, or mushy tissue at the base of the stem or at the crown, sometimes with a sour smell. Lift a failing plant and look at the roots: healthy ones are firm and pale, rotted ones are brown or black and slimy, and the outer layer slips off between your fingers leaving a thread of core behind. Seedlings that topple over at soil level are the same problem, called damping-off.

Prevent: Drainage is the whole defense. Match the plant to the site first - something that wants sharp drainage will not survive heavy clay or a low, water-collecting spot however well you tend it. Where the ground is heavy, plant on a raised bed, berm, or slope, or grow in a container. Set plants at the depth they were already growing, since burying the crown or the root flare is a common cause of rot, and keep mulch pulled back a few inches from the stem base instead of piled against it. Water the soil rather than the calendar: check that the top inch or two is dry before watering again, cut back hard in cool weather and winter dormancy, and never leave a pot standing in a full saucer. Do not plant or dig in soggy ground, and go easy on rich amendments for plants that want it lean. Rotate annual crops, and start with clean healthy plants and fresh mix.

Treat: There is no cure for tissue that has already rotted, so act on the conditions rather than looking for a spray. Stop watering at once and fix the drainage - open up compacted soil, or move the plant to a raised, sharply drained position or a container. Lift a badly affected plant, cut away every soft dark root and rotted section with a clean blade back to firm pale tissue, and replant only the healthy parts into fresh free-draining soil or mix. Often the better move is to give up on the plant and save its offspring instead: cuttings, offsets, or divisions taken from firm healthy growth root readily and give you a clean start. Bin the rotted material rather than composting it, and correct the drainage before you replant, because the rot comes straight back in the same wet spot.

Phytophthora is the specific killer of azaleas and the commonest cause of a shrub that simply dies for no visible reason. Almost every case traces back to planting too deep or in ground that does not drain: set the root ball an inch or two above grade, build a raised bed on clay, and never plant one in a low spot.

Not an infection but a nutrient lockout caused by soil chemistry. Iron is abundant in almost every soil, but as pH rises it converts to forms roots cannot take up, so a plant that needs acid ground slowly starves for iron while standing in soil full of it. The symptom is unmistakable: new leaves go pale yellow or cream while the veins stay green, giving a fine green net over a yellow leaf. It shows first and worst on the newest growth, because iron does not move around inside a plant to be recycled. It does not spread between plants, does not respond to fungicides, and does not resolve on its own - left uncorrected the plant grows less each year, leaves get smaller and paler, shoot tips die back, crops fall away, and it eventually dies. Worst near concrete, mortar, paths and limed ground, and in cold, wet, compacted soil.

Watch for: Yellow leaves with a distinct network of green veins, worst on the NEWEST growth at the shoot tips - that vein pattern is what separates it from a nitrogen shortage, which yellows the oldest leaves uniformly. Whole plants going progressively paler over a season rather than suddenly. Brown scorched leaf margins and shoot-tip dieback in advanced cases. Symptoms concentrated on the side of a plant nearest a foundation, wall, path, driveway, or a stretch of limed lawn. One plant affected while a neighbor that does not need acid soil looks perfect.

Prevent: Test the soil pH before you plant, not after, and match the plant to the ground - an acid-loving plant in limy soil will never be truly healthy however it is fed. Where the pH is too high, acidify with elemental sulfur worked in the season BEFORE planting, since sulfur takes months of soil biology to work and cannot be rushed, and retest before you commit plants. On genuinely alkaline ground the honest answer is often a raised bed of acidic mix, or a container, rather than fighting the native soil forever. Keep an acidic organic mulch topped up - pine bark, pine straw, sawdust - and site acid-lovers away from concrete foundations and mortared walls, which leach lime for decades. Never apply lime, wood ash or mushroom compost where the roots reach, use acid-forming fertilizers such as ammonium sulfate, and improve drainage, because cold waterlogged soil hurts uptake even at the right pH.

Treat: Correct the soil, and use iron only to buy time. Chelated iron sprayed on the leaves or drenched into the root zone greens a plant up within a week or two, but it wears off in a season and has to be repeated indefinitely - it fixes nothing. The real fix is lowering pH with elemental sulfur applied to the surface and watered in, retesting each season until you are in range, then holding it there with acidic mulch and acid fertilizer. Expect one to two years; there is no fast route. Note that other shortages look identical - manganese deficiency produces the same yellow-with-green-veins pattern on some plants - so a plant that does not green up from iron should be tested rather than dosed again. Where the pH is high because of nearby concrete or genuinely calcareous subsoil, the plant is in the wrong place, and moving it into a properly built acidic bed or container will succeed where years of amendment will not.

Azaleas need a pH around 4.5-6.0 and go chlorotic quickly above it - which is why they fail so consistently in alkaline-soil regions and next to concrete foundations and paths that leach lime. Test before planting; a raised bed of composted pine bark is a better answer than years of chelated iron.

Lace bugs are small flat sap-suckers with clear, intricately veined wings that sit on the undersides of leaves and drain them one cell at a time. You almost never notice the insect first - what you see is the leaf going pale and stippled from above, as though the colour had been lifted out of it in fine dots, while the underside carries scattered hard black specks of varnish-like excrement along with the shed skins of the nymphs. Several generations run through a single season, so damage accumulates from late spring onward and a badly attacked plant looks bleached and exhausted by August. Damaged leaves never re-green. Above all this is a pest of plants growing in more sun, heat, and drought than they want: the same shrub in cool part shade with steady moisture often carries almost none.

Watch for: Pale stippling or fine white speckling across the upper leaf surface, worst on the leaves most exposed to sun. Hard shiny black specks and rusty cast skins on the leaf undersides - the confirming sign, and what separates lace bugs from spider mites, which leave fine webbing instead. Small flat insects with lacy transparent wings on the undersides when you turn a leaf over. Whole plants looking bleached, grey-green, and tired by midsummer, with the worst of it on the sunny, dry side. Early leaf drop and thin, weak growth on plants attacked hard several years running.

Prevent: Siting does most of the work. Plants grown in cool part shade with steady moisture and a good mulch carry a fraction of the lace bugs that the same plants carry in hot afternoon sun and dry soil, so move a chronically infested shrub rather than spraying it every year. Keep the root zone mulched and evenly watered right through summer. Avoid broad-spectrum insecticides, which remove the lacewings, predatory bugs, and spiders that hold lace bug numbers down. And turn a few leaves over in late spring, when the first generation is small and easy to deal with, rather than waiting until the plant has gone pale.

Treat: Treat early, and treat from below. Insecticidal soap or horticultural oil kills lace bugs on contact but only where it lands, so the spray has to reach the leaf undersides; go after the first generation in late spring rather than the bleached plant in August, and repeat after seven to ten days. A strong jet of water on the undersides knocks nymphs off and helps. Foliage that is already stippled will not recover its colour - it stays that way until it drops, so judge success on the new growth, not the old. Anything you spray must be labeled for the plant you are treating. Where a shrub is hit badly every single year, the honest fix is more shade and more water, or a different plant in that spot.

The defining azalea pest, and effectively a siting diagnosis: azalea lace bug populations explode on shrubs planted in full afternoon sun and dry soil, and collapse on the same cultivar grown in moist part shade. Check the undersides in late May before the plant goes pale.

Petal blight is a fungal disease of the flowers alone - leaves, stems, and roots are untouched - which makes it particularly galling on a shrub grown for two weeks of bloom. Spores landing on open petals during warm, wet, humid spring weather produce small pale spots that within a day or two swell into limp brown blotches, and the whole truss collapses into a slimy brown mass that then hangs on the plant for weeks instead of dropping cleanly. A blighted petal rubbed between the fingers feels slippery and tissue-like, quite unlike the dry papery brown of frost damage or ordinary fading. The fungus overwinters as hard black resting bodies in the fallen flowers and the top of the mulch beneath the plant, which is why it returns to the same shrub year after year - and why the litter under the plant is the whole story.

Watch for: Small pale or watery spots on open petals - white spots on coloured flowers, rust-brown on white ones - appearing during a warm wet spell at peak bloom. Flowers going limp, brown, and slimy within a day or two rather than drying papery at the edges the way frost or age leaves them. Collapsed trusses clinging to the shrub instead of dropping. Leaves and shoots completely unaffected while the flowers are ruined: that contrast is the identifying feature. A plant that does the same thing at the same point every spring, especially in a still, shaded, crowded corner.

Prevent: Clean up the litter. The fungus survives in fallen petals and the surface of the mulch, so rake out and bin every blighted flower and the old mulch beneath affected plants after bloom and lay a fresh layer - that alone breaks most of the cycle in a home garden. Water at the base rather than over the flowers and keep sprinklers off anything in bloom. Thin crowded plantings so air moves through, and avoid planting new shrubs tight against an old, chronically affected one. Where the disease shows up every year, planting later-blooming varieties that flower after the wettest weather has passed is a genuine fix rather than a workaround.

Treat: Nothing sprayed onto a blighted flower will bring it back, so treatment is really about next spring. Pick off collapsed trusses as they appear and bin them rather than composting them, then strip and replace the mulch once bloom is over. Where a valued plant is ruined annually, protective fungicides do work, but only preventively - they have to go onto the flower buds as colour first shows and be repeated through bloom, which is a demanding schedule for an ornamental. Follow the label for the plant you are treating. For most gardens the honest answer is sanitation, better airflow, watering at the base, and accepting that a warm wet spring will cost you some flowers.

Ovulinia azaleae is the azalea specialist, and it is worst in the humid Southeast where a warm wet spell lands on peak bloom. The single most effective home measure is stripping the fallen petals and the old mulch out from under the shrub after flowering.

Spider mites are not insects but tiny sap-feeding arachnids, smaller than a grain of salt, and you almost always notice the damage before you notice them. They live on the undersides of leaves and drain the cells one at a time, which is why the leaf goes finely stippled with pale dots before it bronzes and dries. They breed explosively in hot, dry, dusty, still air - a generation can pass in a week at high temperature - so a barely visible population becomes a webbed, bronzed plant within a fortnight. Drought-stressed plants and plants wintered indoors in dry heated air are the classic hosts. Broad-spectrum insecticides make matters worse rather than better, because they kill the predatory mites and lady beetles that normally hold mites in check.

Watch for: Fine pale stippling or speckling across the upper leaf surface, as though the color had been sandblasted out of it, and later a dull bronze or rusty cast over the whole leaf. Delicate webbing across leaf joints, shoot tips, and undersides - that comes with a heavy infestation and means you caught it late. Leaves that dry, curl, and drop early while the plant looks thirsty no matter how much you water it. Hold a leaf over a sheet of white paper and tap it: the specks that fall and then start walking are mites. With a hand lens, look on the undersides for the mites themselves, pale or reddish, and their round translucent eggs. Damage that shows up first on the hottest, dustiest, most sheltered side of a plant, or on a pot sitting near a radiator indoors.

Prevent: Do not let plants get drought-stressed - that is the single strongest trigger, and a plant watered steadily through heat is far less likely to have a mite problem at all. Hose the foliage down, undersides included, during hot dry spells: it knocks mites off, washes away the dust they thrive in, and raises the humidity around the plant for a while. Indoors and under cover, keep the air from going hot, dry, and stagnant, wipe or rinse the leaves occasionally, and keep pots away from radiators and heating vents. Inspect any plant carefully before you bring it indoors for winter or set it among others, since mites almost always arrive on something else. Avoid broad-spectrum insecticides: they wipe out the predatory mites, lacewings, and lady beetles that do most of this work for you, and reliably leave you with a worse outbreak than you started with.

Treat: Start with water. A strong jet aimed at the leaf undersides, repeated every few days for a couple of weeks, knocks populations down and breaks the cycle - on many plants that alone ends it. On anything that regrows quickly, shearing back badly infested growth resets the plant to clean foliage. If it keeps building, spray insecticidal soap or horticultural oil directly onto the undersides where the mites actually live, and repeat every five to seven days for three rounds: contact sprays do not kill the eggs, so a single application always fails. Anything you spray must be labeled for the plant you are treating - follow the label and observe its pre-harvest interval on anything you eat. Predatory mites are an effective release in a greenhouse or on an indoor plant. Above all, correct the heat, dust, and drought stress that caused it, or the mites simply come back.

Southern red mite is the azalea species, and unusually it peaks in the cool of spring and autumn rather than midsummer. The stippling looks much like lace bug damage - check the undersides, because lace bugs leave hard black specks and mites leave fine webbing.