Gadenin日本語Get the appCrown and basal rot: the one that kills fastest
Bacterial rot is the main killer of paphiopedilums indoors, and it enters through the funnel at the center of a fan where water collects. The first sign is a soft, water-soaked, slightly translucent patch at the base of the newest leaf, often with a foul smell if you put your nose to it. It spreads downward through the growing point within days, and a fan that is affected at the base is usually beyond saving.
Act the moment you see it. Take the plant somewhere dry and airy, cut away every soft leaf and all discolored tissue with a sterilized blade until you reach firm, clean, white or green material, and sterilize the blade again between cuts. Leave the wounds open to dry rather than dressing them, and dust the cut surfaces with cinnamon or a powdered fungicide if you have one. Withhold water from the crown entirely and water only at the pot edge afterwards.
If one fan is lost but the plant has others, cut the affected fan away at the base and keep the rest. Then fix the cause: water at the pot edge, water in the morning, and put some air movement into the room. Rot that recurs is nearly always a watering habit rather than bad luck.
Cold plus wet is the combination that starts most rot. A plant watered in the evening in a room that drops to 55F (13C) overnight, with still air, is at real risk even if the crown looks dry. Move watering to the morning through the cool months.
Insects: mealybugs and scale, mostly hidden
Mealybugs are the pest you will actually meet. They look like small white specks of cotton wool and they hide in exactly the places you do not look: deep between the leaf bases, in the crown, and down among the roots. A plant that seems clean from above can be heavily infested at the base, and sticky residue or sooty black mold on the leaves is often the first clue.
Scale insects appear as flat brown or tan discs stuck to the leaf undersides and along the midribs, and they do not move. Both are dealt with the same way: wipe every accessible insect off with a cotton bud dipped in rubbing alcohol, then treat the whole plant with insecticidal soap or a horticultural oil, and repeat every seven days for at least four cycles to catch newly hatched crawlers. One treatment never works.
Fungus gnats, small dark flies drifting up from the pot, are a sign the mix is staying too wet or has broken down rather than a pest of the plant itself. The adults do nothing; the larvae chew fine roots. The answer is to repot into fresh open mix, not to reach for a spray. Slugs and snails, which chew the edges of leaves and eat flower buds overnight, come indoors on plants that have summered outside and need finding by torchlight.
| Symptom | Likely cause | What to do |
|---|---|---|
| Soft translucent patch at the base of the newest leaf | Bacterial crown rot | Cut back to firm tissue at once, dry the crown, water at the pot edge only |
| White cottony specks between leaf bases | Mealybugs | Alcohol on a cotton bud, then insecticidal soap weekly for four weeks |
| Flat brown discs on leaf undersides | Scale insects | Scrape off, then horticultural oil at weekly intervals |
| Dry brown leaf tips on healthy foliage | Salt build-up from hard water or feed | Flush the pot with plain water monthly and change water source |
| Small sunken black spots with yellow haloes | Fungal leaf spot | Cut out the spotted area, improve air movement, keep foliage dry |
| Leaves streaked or blotched with pale mosaic | Virus | Isolate and discard; there is no treatment |
Brown tips, black tips and other marks that are not disease
Dry brown leaf tips with a clean edge, on foliage that is otherwise firm and green, are almost never a pathogen. They are salt damage, caused by hard water, softened water or too much fertilizer accumulating in a mix that is kept constantly damp. The fix is a thorough monthly flush with plain water and, if you can, a change to rainwater or filtered water. Trim the dead tissue back to just inside the green if the look bothers you, using sterilized scissors.
Blackened root tips found at a repot are the same story underground, and they are the earlier warning. If you see them, tighten up the flushing routine before the leaf tips start to go.
Bleached, papery patches in the middle of a leaf are sunburn from direct light, and they will not heal but do no further harm. Pleated or accordion-shaped new leaves mean the plant was short of water while that leaf was expanding. Neither is contagious and neither needs cutting out.
Virus, and knowing when to give up
Orchid viruses show as pale or dark mosaic streaking, ring patterns, or sunken necrotic flecks that follow the length of the leaf rather than sitting as discrete round spots. There is no cure. A virused plant will decline slowly and, more importantly, will pass the infection to every other orchid you cut with the same blade or handle with sap on your fingers.
This is why sterilizing tools between plants matters so much. Use a fresh disposable razor blade for each plant, or flame a knife until it glows, and wash your hands after handling any plant you are unsure about. Do not reuse pots or stakes between plants without sterilizing them either.
Give up on a plant when the crown has rotted through on a single-fan plant, when virus is confirmed, or when there are no living roots and no firm growing point left. Everything else is worth attempting, because a paphiopedilum with even one sound fan and a few live roots will rebuild given a fresh open mix and steady conditions.
A weekly look and a written note
Once a week, when you water, spend thirty seconds actually inspecting: run a finger into the crown to check it is dry, turn a couple of leaves over to look at the undersides, and check the base of the newest fan. Almost every problem in this list is trivial to fix in the first week and serious by the fourth.
Write down what you find and when. Note the date you first see a pest, the dates of each treatment so you keep to the seven-day cycle, and the date any rot appeared alongside what the watering and temperature had been. Pests come back at the same time of year, and a note from last winter tells you when to start looking rather than when to start reacting.