Gadenin日本語Get the appSuspect the roots before anything else
A sage that wilts, goes dull gray-green and does not recover overnight is nearly always rotting at the root, not thirsty. The confusion is deadly, because the natural response is to water it and that finishes the job within days. Root and crown rots take hold in soil that stays wet, especially over winter or after a run of heavy summer storms on heavy ground.
Check before you water. Scrape two inches down beside the plant: if the soil there is damp and the plant is still wilting, the problem is the roots. Pull a small plant and look at them. Healthy sage roots are firm and pale; rotted ones are brown, soft and pull away from the core with a smell of stagnant water. A plant that far gone does not recover, so take cuttings from any clean top growth immediately and replace it, in a different, better-drained spot.
| Symptom | Root rot | Genuine drought |
|---|---|---|
| Soil two inches down | Damp or wet | Dry and crumbling |
| Recovery by evening | None | Full recovery once it cools |
| Leaf color | Dull gray, then brown from the base up | Green but folded and limp |
| Base of stem | Dark, soft, sometimes sunken | Firm and normal |
| What to do | Do not water; take cuttings and replace | Soak thoroughly once |
Rot organisms persist in the soil. Do not replant sage or any other Mediterranean herb in the same spot without raising the bed or forking in a lot of grit first.
Powdery mildew in still, crowded plants
White dusty patches on the upper leaf surface, spreading until whole shoots look floured, is powdery mildew. On sage it is a disease of stagnant air and of plants that have grown too dense in the middle, and it is worst in the warm days and cool, damp nights of late summer. Dry roots make it worse rather than better, which is why it often shows on a container plant that has been allowed to go bone dry between waterings.
- Cut out the affected shoots straight away Remove infected growth back to clean wood, above a live shoot, and bin it rather than composting it. Half an hour of cutting in the first week saves the plant; leaving it a fortnight rarely does.
- Open the middle of the plant up Thin crossing and inward-facing stems so air moves through the center. Mildew almost never takes hold on a plant that is properly pruned and correctly spaced.
- Water the soil, never the leaves Overhead watering leaves the foliage damp into the night. Water at the base, in the morning, so any splash has dried by dusk.
- Stop feeding Soft, nitrogen-fed growth is the tissue mildew colonises first. If you have been feeding a container plant, stop for the rest of the season.
Sap feeders: what to ignore and what to act on
Sage carries a small cast of sap-sucking insects, and most of them do less harm than the treatment would. The exception is anything that arrives in numbers on a young plant, or anything that leaves the leaves distorted rather than merely marked. Look under the leaves, because that is where nearly all of them sit.
| What you see | Cause | What to do |
|---|---|---|
| Blobs of white froth on stems in early summer | Spittlebug nymphs | Cosmetic. Hose off if you dislike it; no treatment needed |
| Small ragged holes and puckered, distorted young leaves | Capsid bugs | Cut off distorted tips; damage stops as the season goes on |
| Pale mottled stippling on the upper surface | Leafhoppers | Tolerate on established plants; wash off on young ones |
| Clouds of tiny white insects under the leaves | Whitefly, mainly on plants brought indoors | Rinse the undersides; improve ventilation and light |
| Sticky leaves with fine webbing in hot dry spells | Spider mite | Raise humidity, hose the plant down, cut out the worst shoots |
A healthy sage in full sun on poor soil is rarely troubled by any of these. Repeated pest problems usually point back to too much shade, too much feed or too little air.
Chewed leaves: beetles, caterpillars and slugs
Metallic green and purple striped beetles feeding on the shoot tips of sage, rosemary and lavender are rosemary beetles, and both the adults and the gray grub-like larvae eat foliage. They are slow and easy to see. Shake the plant over a sheet of paper or an upturned lid on a warm afternoon and collect what falls, and repeat weekly through late summer and autumn when they are most active. On one or two garden plants, hand collecting is genuinely enough.
Slugs and snails matter only on seedlings and freshly rooted cuttings, where they can clear a tray in a night. Once a plant is woody at the base they largely leave it alone. Ragged holes in mature leaves with green droppings nearby are caterpillars: find and remove them, and expect no further trouble.
- Check the shoot tips weekly in late summer Beetles feed at the tips where the new growth is. A weekly look at the top few inches of each plant catches an infestation while it is still a handful of insects.
- Protect seedlings, not mature plants Keep young plants off the ground on a bench or ring them with grit. Spending effort on slug control around an established sage is wasted.
- Clear fallen debris under the plant Beetle larvae drop to the ground to pupate and slugs shelter in leaf litter. A gravel mulch kept clear of fallen leaves removes both hiding places at once.
Knowing when a plant is finished
Not every sick sage is worth saving, and the commonest mistake is nursing a plant for two seasons that should have been replaced in an afternoon. If the base is bare woody stems with no shoots low down, if the center has collapsed outwards, or if the roots are brown and soft, the plant is done. Sage does not reliably regrow from old wood, so there is no rescue prune that will bring it back.
The right response is always the same: take healthy cuttings from whatever clean growth remains, root them, and dig the old plant out. A cutting taken in summer is a usable plant by the following spring, which is faster than any recovery you could coax out of a failing three-year-old.
Record the date and the symptom each time a plant fails, along with where it was growing. Two or three entries usually reveal a single cause, and it is nearly always the wettest position in the garden.