White Sage

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.

For white sage the trigger is SUMMER irrigation, not winter wet - warm soil plus water is exactly what Phytophthora needs, and this is the single most common way an established plant is killed. Give it nothing between the last spring rain and the first fall rain, keep it off shared sprinkler valves and away from lawn spray and downspouts, plant it high on a slope or raised ground, and never amend the planting hole.

White sage is adapted to a climate with no summer rain and dry summer air, and outside that climate it usually fails within a season or two no matter how carefully it is watered. The problem is not only wet soil but humid, still air: the white hairs that make the foliage so effective at reflecting sun also hold moisture against the leaf surface, and in muggy weather that becomes a fungal nursery. Plants in the humid Southeast, the Midwest, the Gulf, and much of the East Coast typically rot at the crown, mildew, or simply thin away over their first or second summer. This is a climate mismatch rather than a disease to fight, and it is worth knowing before buying rather than after - most white sage sold as a mail-order plant goes to places where it cannot live in the ground.

Watch for: A plant that grows well through spring and then collapses, thins, or blackens with the first muggy weather. Leaves going dark, limp, or spotted rather than silver and firm. Grey mold or fuzzy growth in the crown after a run of warm rain. Persistent mildew that keeps returning after every humid spell rather than clearing in dry weather. Stems dying back one at a time from the base upward through a wet summer.

Prevent: The reliable prevention is the site. In a dry-summer climate, plant on a slope, berm, or raised bed in full sun with wide spacing and free air movement, and give it nothing to drink in summer. In a summer-rainfall climate, do not plant it in the ground: grow it in a gritty, fast-draining pot under an eave or overhang where you control what reaches it, keep it in as much sun and moving air as possible, water only when the mix is dry right through, and move it under cover for a wet winter. Never crowd it, never mulch against the crown, and never water the foliage.

Treat: There is little to do once a plant is failing from humidity, and nothing that changes the climate. Cut out dead and blackened stems back to firm green growth, thin the plant to open it up, and stop all watering. Move a container plant somewhere sunnier, airier, and more sheltered from rain. In the ground in a humid region, treat the plant as an annual, take cuttings or save seed while it is healthy, and be realistic that a replacement will do the same thing. Where the fragrant silver sage is the point rather than the species, a Mediterranean sage or a hardier salvia will give you the effect without the annual funeral.

This is the honest answer to why a mail-ordered white sage died in Georgia or Ohio, and the reason the file's zone band stops where it does. In its own range the plant is close to indestructible; outside a dry-summer climate it is a container specimen at best.

Powdery mildew is a fungal disease that coats leaves - and often stems, buds, and fruit - in a white-to-gray powder that looks like spilled talcum. It is not one fungus but a large family of them, each fairly specialised to its own group of plants, which is why mildew on one crop rarely jumps to an unrelated one beside it. Unlike most leaf diseases it does not need wet leaves: it thrives on warm dry days followed by humid nights, and it takes hold fastest where plants stand crowded in still air or in shade. The coating blocks light, so heavily covered leaves yellow, brown, and drop early. On many plants that is mostly disfiguring and arrives late enough not to matter; where it strips away the leaves a crop still needed to finish, it costs you size, sweetness, and quality.

Watch for: Round white powdery spots on the upper leaf surfaces that spread and merge until whole leaves look dusted. It usually starts on the oldest, lowest, most shaded leaves and works upward, so check there first. Look at the undersides too, and at stems, buds, and flower stalks, which get coated as it advances. Leaves that yellow, brown, curl, or go crisp and drop early under the coating. New growth that opens small, crumpled, or twisted where the fungus has reached the shoot tips. On plants where it gets onto the fruit, a dull gray film, russeted or scarred skin, and cracking. Late in the season, tiny dark specks scattered through the white felt - that is the fungus setting up to overwinter on the debris.

Prevent: Give plants room. Crowding and still air are the biggest single driver, so space at the full recommended distance, thin seedlings properly, and divide or prune out congested growth until air moves through the plant. Full sun and an open position help; deep shade and a still corner against a wall are where it always starts. Water at the base rather than overhead, and water early in the day so nothing stays damp overnight. Keep plants evenly watered - drought stress at the roots leaves them far more susceptible, even though the fungus itself likes dry air. Go easy on nitrogen, since soft lush growth is the most vulnerable. Where resistant varieties exist for what you are growing, choosing one is the single most effective thing you can do on a plant that mildews every year. Clear infected leaves and stems away at the end of the season rather than composting them.

Treat: Start early: sprays protect healthy tissue, they do not clean up leaves that are already coated. Pick off and bin the worst leaves as soon as you see them, and open the plant up by thinning or pruning so air moves through. On anything that regrows quickly, shearing the whole plant back forces a clean flush and beats spraying. If it keeps spreading, potassium bicarbonate, horticultural oil, or neem applied weekly will hold it - cover both leaf surfaces. Sulfur also works, but it burns the foliage of some plants, should never go on in heat, and must not be mixed with or applied close behind an oil spray. Whatever you use must be labeled for the plant you are treating: follow that label and observe its pre-harvest interval on anything you eat. Do not compost badly infected material. Late-season mildew on a plant that is finishing anyway is usually cosmetic; on a crop still filling out it is worth acting on.

Turns up on soft spring growth in a cool damp spring, in a crowded planting, or in shade, and the dry season normally ends it. Note that the shearing remedy does NOT apply here: white sage cannot resprout from bare wood, so open it up by thinning and spacing rather than cutting it back. A plant in full sun on lean ground with air moving through it rarely shows mildew at all.

White sage, like most California chaparral and coastal-sage subshrubs, does not reliably resprout from bare, leafless old wood. Any cut placed below the lowest green leaves usually kills that stem outright, and a plant sheared hard all over often dies with it. This catches out two kinds of gardener: the one applying the hard renewal cut that works on lavender or butterfly bush, and the one harvesting leaves too enthusiastically or too young. Because the plant is naturally short-lived and goes woody and open with age, the temptation to cut it hard arrives exactly when it is least able to survive it. Light, high, well-spread cuts on an established plant are safe; low ones are not.

Watch for: Cut stubs of bare gray wood still bare weeks later, with no shoots breaking anywhere along them. Whole branches browning and dying back to the base in the weeks after a harvest or a shearing. A plant that looked fine when cut and is dead by the following spring. A bald flank where one side was harvested repeatedly. An old, woody, open plant with green only at the branch tips - the state in which hard renovation pruning looks like the obvious fix and is fatal.

Prevent: Keep every cut above green leafy growth, without exception - this applies to harvesting, deadheading, and tidying alike. Do not cut from a plant under about three years old, take no more than roughly a third of an established plant in a season, and spread the cuts around the shrub rather than working one side. Pinch young plants a couple of times in their first year so they branch low and full, which removes the reason to renovate later. Give the plant three to five feet of room so you are never pruning to control size, and keep it lean and unwatered so growth stays firm rather than soft and leggy.

Treat: Nothing brings back a stem cut into bare wood. Remove the dead stubs cleanly at their base and let the remaining growth fill in. If a whole plant was cut hard, leave it strictly alone - and in particular do not water it to encourage recovery, which finishes off a stressed chaparral plant faster than the pruning did - then wait a full season before writing it off. Once a plant is genuinely spent, replace it: seed sown in fall is easy, self-sown volunteers are better still, and a young plant reaches cutting size in about three years.

Nearly every 'my white sage died after I harvested it' story is this. The rule is short enough to remember at the shears: never cut where there are no green leaves below the cut.

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.

Almost always a container or nursery problem here rather than a garden one, and worst on dusty plants in still air. Hose the leaf undersides down in a heat wave. Two of the shared remedies do not apply to a white sage in the ground: do not shear it back, since it cannot resprout from bare wood, and do not start summer irrigation to cure drought stress - a dry-looking August plant is resting, not thirsty.