Camellia

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 root rot kills more camellias than cold does, and planting too deep is usually how it starts. Set the top of the root ball an inch or two ABOVE grade, mound soil up to meet it, and never let the trunk flare be buried or mulched over. Heavy clay and a low spot are both fatal - build a raised bed instead. A shrub that wilts, yellows and dies back on one side in wet ground is telling you this.

Scale insects are sap-suckers that spend most of their lives immobile, fixed to a stem, twig, or leaf underside beneath a waxy or shell-like cover. They look far more like bumps, blisters, or crusty encrustations than like insects, which is why an infestation is usually well established before anyone notices it. Soft scales excrete large amounts of sticky honeydew that drips onto everything below and grows a black sooty mold - and those blackened leaves are often the first thing a gardener actually sees. Armored scales produce no honeydew but sit under a hard shield that protects them from most sprays. They spread as tiny mobile crawlers in the weeks after hatching, which is the only stage that moves and the only stage that is easy to kill. Populations build on stressed plants, on crowded shaded growth, and above all on plants kept indoors in dry, still air over winter.

Watch for: Rows of small brown, tan, black, white, or waxy bumps along stems, twigs, leaf midribs, and leaf undersides that do not brush off but can be scraped loose with a fingernail. A sticky shine on the leaves - and on the floor, table, or path beneath the plant - that later turns black with sooty mold. Ants running steadily up and down the stems, since they farm and defend scale for that honeydew; often the first sign anything is wrong. Yellowing leaves, weak thin growth, and dieback of individual branches or canes that are heavily encrusted. On fruit crops, scale covers and sooty mold directly on the fruit. Check the leaf undersides and the shaded inner wood, which is where colonies build up unseen.

Prevent: Inspect. Look over leaf undersides and stems regularly - on a crop you pick, every harvest is a scouting chance - and check every new plant thoroughly before you buy it, plant it, or set it beside anything else, because scale almost always arrives on a plant rather than flying in. Quarantine new houseplants for a few weeks. Keep plants unstressed and not over-fertilized, since soft, forced growth is what populations build on. Prune for airflow and light to open up the shaded inner growth where scale hides, and prune out heavily infested wood as routine maintenance - on anything that gets a hard annual pruning, that alone removes most of any buildup. Leave the lady beetles, lacewings, and parasitic wasps alone, since they normally keep scale down to nothing, and keep ants off the plant where you can, because ants protect the colonies from those predators. Indoors, avoid hot, dry, still winter air.

Treat: Horticultural oil is the main control: it works by smothering, so it has to coat the insects thoroughly - stems, twigs, and leaf undersides - and it usually needs repeating, because the waxy covering shields them and no single pass reaches everything. On deciduous woody plants a dormant-season oil smothers the overwintering stage while the leaves are out of the way, and timing a growing-season spray to the crawler stage, when the young are mobile and uncovered, is far more effective than spraying settled adults. On a small plant or a light infestation, scrub or wipe the scales off by hand, or dab them with a cotton swab of rubbing alcohol. Prune out and destroy badly encrusted wood rather than trying to save it. Wash off the sooty mold once the scale is gone - it lives on the honeydew, not on the plant, and stops once the supply does. Anything you spray must be labeled for the plant, and oils can burn delicate foliage, so test first.

Tea scale is THE camellia pest across the South. It packs the leaf UNDERSIDES with white and brown specks, so the first thing most people see is yellow mottling on the upper surface and sooty black film on the leaves below. Turn a mottled leaf over before doing anything else. Thorough oil coverage of the undersides timed to the crawlers, plus thinning the shrub for light and air, is the control; a badly encrusted interior branch is better pruned out.

Camellia petal blight is caused by the fungus Ciborinia camelliae, and it attacks the flowers only - the shrub itself stays perfectly healthy while every bloom rots. Small brown specks appear on the petals and enlarge into blotches that spread from the base of the flower outward, until the whole bloom goes leathery brown and drops, often within a day or two of opening. The petal veins stay noticeably darker than the tissue between them, which is what separates blight from ordinary freeze damage. The fungus overwinters as hard black bodies called sclerotia in the fallen flowers and the top inch of soil under the bush, and releases its spores in late winter and spring, exactly when the flowers open. It travels on the wind and arrives in bought plants, and once it is loose in a garden it is very difficult to be rid of.

Watch for: Brown blotches spreading from the base of the flower outward, with the petal veins staying darker than the tissue between them - unlike frost, which browns the outer petal edges first and hits only the blooms that were open during the freeze. Flowers going leathery brown and dropping whole within a day or two of opening. A ring of collapsed brown blooms on the ground under the shrub. Small hard black lumps about the size of a lentil in last year's fallen flowers and in the litter underneath. Bloom after bloom affected while the leaves, stems and buds stay entirely healthy - that is the signature of this disease and rules out root or scale problems.

Prevent: Sanitation is the whole defense. Pick up every fallen flower every few days through the entire bloom season and bin or burn them - never compost them and never leave them lying under the shrub, because that is precisely where next year's infection is made. Pick the spent flowers off the plant too, since japonicas hold on to them. Each fall, rake off and replace the top few inches of mulch and litter, then mulch 3 to 4 inches deep, which buries any sclerotia too far down to shoot. Avoid overhead watering while the shrub is in bloom. Sasanquas, which flower earlier and shatter their petals, escape much of the damage, so they are the better choice in a badly affected garden. Inspect any new camellia and remove its flowers and the surface of its potting mix before planting.

Treat: No spray cures an infected flower, and fungicide programs are impractical at home - the blooms open over months and each one would need protecting individually. What works is relentless removal: strip and bin blighted blooms as they appear, keep the ground under the shrub clear, and refresh the mulch every autumn. Do not move soil, mulch or fallen flowers from an affected shrub to another part of the garden, and do not give away rooted cuttings in that soil. Expect improvement over several seasons rather than a fix in one, and understand that where the disease is widespread, spores blowing in from neighboring gardens make this something you manage rather than eliminate.

The commonest serious camellia problem across the Southeast and the Pacific Northwest. Japonicas suffer most because they hold their spent flowers; sasanquas shatter and escape much of it. The disease never harms the shrub, only the display.

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.

Camellias want soil around pH 5.0 to 6.5, and yellow leaves with green veins on the newest growth are the usual sign the ground is too sweet - most often beside a concrete foundation, a mortared wall or a limed lawn. Test before planting rather than after. Chelated iron greens the shrub for a season; elemental sulfur plus a pine bark or pine straw mulch is what actually fixes it.

Bud drop is the commonest camellia complaint and it is a disorder rather than an infection: the shrub sets a heavy crop of flower buds in late summer and then sheds them whole and unopened over the following weeks. The usual cause is water. Camellias form their buds in July, August and September, and a dry spell in that window leaves the plant unable to carry what it made. Sudden hard cold, a plant standing in soggy ground, too much nitrogen, root disturbance, and simply setting more buds than the shrub can finish all produce the same result. Some varieties, particularly the very large formal doubles, drop routinely. It is disappointing rather than dangerous, and a shrub that drops one year usually flowers normally the next once the summer watering is corrected.

Watch for: Fat, well-formed flower buds falling off whole and unopened, often with a short piece of stem attached, from late fall through winter. Buds browning at the tip and drying without ever opening. A heavy set visible in September followed by a bare shrub in January. Damage worst after a dry late summer, on a plant in a container, or on one planted where roof runoff soaks the ground. Leaves that look entirely healthy throughout - if the foliage is yellowing or whole branches are dying back, the problem is at the roots instead and this is not what you are looking at.

Prevent: Water through late summer. The single most useful thing you can do for next winter's flowers is keep the soil evenly moist in July, August and September while the buds are forming - a slow soaking once a week and a 2 to 3 inch mulch of pine bark or pine straw covers most of it. Feed lightly with an acid fertilizer after bloom and stop by midsummer, since late nitrogen pushes growth at the expense of flowers. Make sure the drainage is genuinely good, because wet feet cause bud drop as reliably as drought does. Shelter the shrub from wind and from sudden hard freezes. And disbud the heavy setters: pinching off all but the strongest bud in each cluster, once they are pea-sized, gives fewer but far more reliable flowers.

Treat: There is nothing to apply once the buds are falling - the cause was months earlier. Do not respond by fertilizing, which makes matters worse. Check the drainage and the mulch, correct next summer's watering, and thin the buds on varieties that habitually over-set. If buds are browning at the tips after a freeze rather than dropping green and intact, that is cold damage rather than this disorder, and the answer is siting: out of direct early-morning sun so frozen tissue thaws slowly, out of the wind, and at the cold edge of the range under the shelter of a wall or evergreens.

Very large formal doubles and any shrub in a container are the habitual offenders. If your camellia dropped its buds this winter, the fix belongs to next August, not to this week.