Gypsophila Problems: Root Rot, Wet Acid Soil, Aphids and Mildew

Root and crown rot, the one that actually kills

A plant that was fine last week and is gray, limp and collapsed today has rotted at the base. Pull it and look: the crown will be brown and soft where it meets the soil, and the taproot will be dark, mushy and easily broken instead of firm and pale. There is no treatment and no recovery, and it is the way most gypsophila dies.

The cause is soil that stayed wet, and it is worse in winter than in summer because the plant is dormant and using no water. Heavy ground, a compost mulch pushed against the collar, a low spot where water sits, a plastic pot with a blocked drainage hole and a peat based compost are all the same problem. Acid soil compounds it, which is why the plant that fails is so often in ordinary, well meaning, improved border soil.

Prevention is all there is. Grit in the soil, a raised crown, a gravel collar rather than a soft mulch, no overhead watering onto the base, and lime to keep the pH at 7.0 to 7.5. Do not replant gypsophila into the exact spot where one has rotted without first fixing the drainage, or the replacement goes the same way.

Before you water a limp gypsophila, push a finger two inches into the soil. If it is damp there, the plant has rot rather than thirst, and watering it finishes it off faster. This one check saves plants every summer.

Aphids, leafhoppers and thrips

Aphids cluster on the soft growing tips and around unopened flower sprays in early summer, and on a fine stemmed plant like this they distort the sprays noticeably as they open. Squash the first colonies between finger and thumb and leave it a week before doing anything else. The open flowers pull in hoverflies and ladybirds in numbers, and their larvae usually finish the job.

Leafhoppers matter less for the feeding damage, which is a fine pale stippling on the leaves, than for what they carry. They spread a disease that turns flowers green and leafy and stunts the whole plant, and there is no cure for an infected plant. Pull and bin anything showing green, distorted, leafy flowers instead of composting it, and keep weedy grass down around the bed, which is where the insects overwinter.

Thrips rasp at the petals and leave the open flowers flecked and browned at the edges, worst in hot dry spells. On gypsophila the damage is cosmetic but it ruins cut material. Cutting the affected sprays off and removing them from the bed breaks the build up, and a plant that is not drought stressed shrugs the damage off.

1. Check the tips weekly in early summer Turn a growing tip over and look at the underside before the sprays open. Aphid colonies caught at the size of a fingernail are dealt with by squashing; caught at the size of a coin they have already spoiled the sprays.
2. Pull anything with green leafy flowers Flowers that come out green and distorted, on a stunted plant, mean an incurable infection spread by leafhoppers. Bin the plant that day rather than leaving it as a source for the rest of the bed.
3. Keep the surrounding grass short Rough grass and weeds at the edge of the bed shelter leafhoppers over winter. A cut strip around the bed does more than any spray.
4. Leave predators a week to work Gypsophila in flower is a magnet for hoverflies. Spraying in the first week of an aphid outbreak removes them along with the pest and the aphids come back faster.

Powdery mildew, botrytis and rust

Powdery mildew shows as a white dusty film on the leaves, starting low in the plant in late summer, driven by warm days, cool humid nights and still air. A plant crowded in at less than its full spacing gets it every year in the same place. Strip the affected lower growth and take it out of the bed, thin crossing stems to open the middle, and stop watering over the top. Spacing at the full two to three feet is the real preventative.

Botrytis, seen as a fuzzy gray mold on dying flowers and stems, appears in wet summers and in dense sprays that have been left to go over on the plant. It is the reason to keep cutting and to shear the plant back after its main flush rather than leaving spent flowers standing. It also ruins bunches hung too tightly for drying, so tie loose bundles no thicker than your fist.

Rust appears as small reddish brown pustules on the undersides of leaves in humid conditions. It is uncommon and rarely serious. Pick off affected leaves as you see them, remove all dead material from around the plant in autumn so spores do not overwinter there, and improve air movement by thinning rather than reaching for anything else.

Slugs, and the problems that are not problems

Slugs and snails will clear a newly thinned row of seedlings overnight, and the giveaway is a clean cut at soil level with a silvery trail nearby. The vulnerable window is short: once the plants have a firm woody base and stand six inches (15 cm) tall, nothing much bothers them. Water in the morning rather than the evening for that fortnight, keep mulch and weeds a hand's width back from the stems, and go out with a torch an hour after dark on the first two nights.

Several things that look alarming are normal. A perennial that comes up very late in spring, weeks after everything around it, is behaving correctly. A first year plant that makes only foliage and no flowers is doing the right thing. A midday droop in heat that is gone by evening needs no action. And the musty smell of freshly cut stems fades within a day and means nothing.

The genuine emergency is only ever the sudden collapse. If a gypsophila goes gray and limp over a couple of days, check the soil moisture and then the crown before you do anything else, because the wrong response to that symptom is more water.

Write down the date of the first aphid colony, the first mildew and any losses, with the bed they happened in. All three recur in the same places at roughly the same point in the season, and a year of dates lets you act a week ahead of the problem instead of a week behind it.