Climbing Hydrangea

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.

The trap is that a moisture-loving vine still needs air at the roots. Downspout discharge and the splash line under a roof edge are the two spots that catch people out - both keep the soil against a wall saturated all winter. Direct the runoff elsewhere, amend heavy clay generously, and plant a foot out from the footing.

Leaf scorch is not a disease and there is nothing to spray for it. It is what happens when a leaf loses water faster than the roots can replace it: the tissue farthest from the veins - the margins and the tips - dries out first and turns brown and papery, and the browning works inward while the rest of the leaf stays green. Hot sun, dry soil, drying wind, heat reflected off paving or a wall, a small or damaged root system, and a plant sited somewhere sunnier or drier than it wants are the usual causes, singly or together. It also happens in winter on evergreens, when bright sun and wind pull water out of the leaves while the ground is frozen and the roots cannot resupply. Shade and woodland plants, shallow-rooted plants, and anything recently planted scorch most easily.

Watch for: Browning that starts at the leaf edges and tips and spreads inward, with a fairly sharp line between the crisp brown tissue and the green that is still healthy. Leaves and fronds going dry, papery, and crisp rather than soft, yellow, or spotted - that is what separates this from a fungal problem. Damage worst on the side of the plant facing the sun or the prevailing wind and on the most exposed upper leaves, while the shaded interior stays fine. Symptoms appearing sharply after a heat wave, a dry spell, or a bright windy week in winter. Whole leaves or fronds shed early as the plant cuts its losses.

Prevent: Site the plant where it actually wants to be. This is a placement problem far more often than a watering problem, and a shade plant in hot afternoon sun will scorch every summer however much you water it. Give shade and woodland plants part-to-full shade and shelter from hot afternoon sun and drying wind. Keep the root zone consistently moist and mulch it well with leaf litter or another organic mulch, which holds water and keeps the roots cool - the single most useful routine step. Water deeply and thoroughly during dry spells rather than little and often, so moisture reaches the whole root zone. Pay particular attention through the first year after planting, when the root system is small and cannot keep up with the leaves. On evergreens in cold regions, make sure the plant goes into winter well watered, and keep it out of bright, windy, exposed positions.

Treat: Water deeply, mulch, and improve the shade - that is the whole treatment, because there is nothing here to kill. Leaves that are already scorched will not recover, so trim off badly browned foliage or fronds for appearance if you want to; the crown and roots are usually unharmed and push out fresh growth once conditions improve. On a plant that scorches badly every year the answer is to move it rather than to keep watering harder, because the siting is what is wrong. Some plants respond well to being cut back hard, which brings a clean flush of new foliage. And on plants that naturally die back or brown off late in the season, scorching at the end of a dry summer is normal and needs nothing at all.

A wall makes this worse than an open border does: masonry radiates stored heat into the evening and the strip of soil along a footing is the driest ground on the property. A hot west or south wall in the South scorches this vine every summer regardless of watering - the fix is a north or east aspect, not more water.

Climbing hydrangea climbs by aerial rootlets - short adhesive holdfasts that grip a surface directly rather than twining around a support. On brick, stone, block, concrete and mature tree bark that is harmless and remarkably strong. On painted or stained wood siding, shingles and trim it is not: the holdfasts grip the paint film rather than the wood, they hold a permanent damp layer against the boards, and they work into any gap or lap joint. Old, soft or already-failing mortar can be loosened where rootlets penetrate the joints, though the vine does not attack sound mortar. The other half of the problem is weight. A mature vine is genuinely heavy, with side branches standing two to three feet out from the wall, and over time it will pull down gutters, downspouts, shutters, lattice and light trellis. It does not strangle a tree it climbs, because it never twines around the trunk.

Watch for: Paint lifting or blistering behind the vine, and bare wood where a stem has been pulled away. Rootlet residue - a permanent pattern of small dark stubs - left on any surface the vine has been removed from. Damp, dark wood behind the growth, and rot at lap joints and around trim. Mortar crumbling out of the joints of an old wall where stems have worked in. Gutters, downspouts, shutters or a light trellis pulling away from the wall under the load. Stems reaching up under siding, roof shingles or soffits, or wandering into window frames. Side branches standing further out from the wall each year - normal growth, but it is where the weight comes from.

Prevent: Choose the surface before you plant. Solid masonry, brick, stone, block, a concrete retaining wall, a stone chimney or the trunk of a large mature tree are all fine, and are what this vine is for. Painted or stained wood siding, shingles and anything with lap joints are not - if that is the wall you have, build a sturdy freestanding frame a foot clear of it and grow the vine on that instead, so air moves behind. Keep the vine well below gutters, soffits and the roof line from the start, and prune it back to stay there every year after flowering; letting it reach the roof and then reversing that is a far bigger job. Never start it on lightweight lattice or a thin trellis, which the mature weight will pull apart. And site it where you can still reach the top of it with a ladder in ten years.

Treat: Cut the stems through at the base first and let the top growth die and dry for several weeks - dead holdfasts release far more easily than living ones, and you will do much less damage to the surface. Then work the vine off gently from the top down rather than hauling from the bottom. Expect rootlet residue to remain: a stiff brush and repainting is the usual finish on wood, while on masonry the stubs weather off over a year or two. Where a vine has reached the roof line or is loading a gutter, cut it back hard - climbing hydrangea takes hard renovation well - but do it in the weeks right after flowering, and accept that it costs a season or two of bloom because the plant flowers on old wood. If the structure itself is soft or failing, remove the vine rather than trying to manage it in place.

This is the one genuinely consequential decision about growing this plant, and it is made once, at planting. Masonry, stone and big trees: yes. Painted wood siding, shingles and light trellis: no.

Aphids are small soft-bodied sap-suckers - green, black, gray, pink, or waxy white, and mostly wingless - that gather in dense colonies on the tenderest new growth: shoot tips, buds, and the undersides of young leaves. They breed extremely fast in mild weather, so a few can become hundreds inside a week. Their feeding curls and distorts soft growth, and the sticky honeydew they excrete coats everything below and turns black with sooty mold. Ants often farm and defend the colonies for that honeydew. A few aphids are normal on almost any plant and a healthy plant shrugs them off; only dense, persistent colonies do real damage, and some aphids also spread plant viruses as they feed.

Watch for: Dense clusters of tiny insects packed onto shoot tips, flower buds, and the undersides of young leaves. Curled, cupped, or distorted new growth that never opens properly. A sticky shine on the leaves - and on whatever sits under the plant - that later goes black with sooty mold. Tiny white cast skins left behind where a colony has been feeding. Ants running steadily up and down the stems, which is often the first thing you notice. Mottled, streaked, or misshapen leaves that do not grow out can mean a virus the aphids brought with them rather than the feeding itself.

Prevent: Go easy on nitrogen: the soft, lush growth that heavy feeding produces is exactly what aphids breed on. Check new growth once a week through spring and early summer so you catch colonies while they are still small, and rub the first few out with your fingers. Leave flowering plants nearby and skip broad-spectrum sprays - ladybugs, lacewings, hoverflies, and parasitic wasps do most of this work for free, and they only stay if there is something for them to eat. Keep ants off the plant where you can, since they protect aphids from those predators. Water steadily so plants are not stressed, and check any new plant over before you bring it home or move it indoors, since aphids usually arrive on something else.

Treat: Knock the colonies off with a hard jet of water and repeat every few days - on most plants that alone ends it. Pinch out or prune off the worst-infested tips rather than treating the whole plant. If colonies keep rebuilding, spray insecticidal soap or horticultural oil directly onto the insects, covering leaf undersides, and repeat weekly until they are gone; treat early or late in the day, and never spray a wilted or heat-stressed plant. Avoid broad-spectrum insecticides - they kill the ladybugs, lacewings, and parasitic wasps that were about to solve the problem for you, and aphid numbers usually come back worse afterward. Anything you spray must be labeled for the plant you are treating; follow that label and observe its pre-harvest interval. On anything you eat, wash leaves, heads, and buds well before use, since aphids hide down in crowns, folds, and tight growth.

Almost the only insect that bothers this vine, and rarely worth acting on: colonies build on the soft spring shoot tips and collapse under predators by early summer. A hard hose jet is usually the entire treatment, and a vine on a wall is easiest to reach before it gets tall.

This is the commonest complaint about climbing hydrangea, and it is not a fault: the plant is simply slow to start. A young vine spends its first several years building roots and making very little top growth, then begins to climb, and only then begins to flower. Three years is typical before it moves, four to five before the first real bloom, and a plant set into poor or dry ground takes longer still. Gardeners routinely conclude it is dead or defective and dig it up in the second season, which is the single biggest reason people fail with this plant. It cannot be hurried into being a fast screen. What it is instead is a fifty-year vine that flowers in shade where almost nothing else will, and the wait is the price of that.

Watch for: A newly planted vine making a few inches of growth in its first and second seasons and appearing to do nothing at all. Shoots that flop and creep along the ground instead of climbing - normal until the plant finds a surface and starts putting out holdfasts. No flowers for the first three to five years, and only a few in the first flowering season. A vine that has climbed but still does not bloom, which usually means too little light or old wood removed by ill-timed pruning rather than youth. Growth restarting from the base after a hard winter, which resets the clock on an established plant.

Prevent: Buy the largest plant you can and plant it well, because everything here comes down to getting roots down. Rich, moist, well-drained soil improved with compost, a 2 to 3 inch mulch kept clear of the stems, and consistent deep watering through the first three summers do more than anything else. Plant a foot out from the wall rather than tight against the footing, which is the driest soil on the property. Guide the first shoots onto the surface and tie them in loosely until the holdfasts take, since a stem lying on the ground will not start climbing by itself. Do not feed heavily - nitrogen buys leaves, not roots or flower wood. And give it enough light: it does flower in shade, but a vine in deep, dry shade under a dense canopy takes far longer and blooms far less.

Treat: There is nothing to fix here, only to wait out. If a vine has been in three years and is still creeping, check three things: water, whether the shoots are actually in contact with a surface, and whether spring or fall pruning has been removing the wood the flowers come on. Correct those, mulch, and give it two more seasons. Moving an established plant restarts the whole process, so be sure of the position before planting rather than relocating later. If you need cover in the meantime, run an annual vine up the same wall for the first few years and let the hydrangea come through behind it - which is what experienced gardeners do rather than replacing the plant.

Worth saying out loud at purchase: this is a four-year plant. If you want a shaded wall covered next summer, this is the wrong vine and no amount of feeding or watering will change that.