Gadenin日本語Get the appRed blotch, the one to catch early
Red blotch, also called leaf scorch, is the characteristic amaryllis disease and it is a fungus rather than damage. It shows as bright red or reddish-brown streaks and sunken spots on the outer bulb scales, on the base of the leaves, and on the flower stalk. Badly affected stalks bend and crack at the marked point, often collapsing with the buds still closed, and leaves come up distorted with red-edged lesions.
Do not confuse it with normal pigment. Many amaryllis, particularly red-flowered ones, carry a natural reddish flush on the neck and the outer scales, and on new leaves as they emerge. The difference is that natural pigment is smooth and even, while red blotch is raised or sunken, has a defined edge and gets worse as the tissue underneath dies.
There is no cure once it is inside a bulb, but it can be controlled. Peel off every affected outer scale until you reach clean white tissue, cut out any lesion on the basal plate with a sterile blade, and let the bulb dry for a day. A soak of the bulb in a systemic fungicide before replanting knocks it back further. Repot into fresh compost and a clean pot, never back into the old compost.
It spreads in water, so the practical prevention is to water around the rim rather than over the crown, keep the leaves dry, space plants so air moves between them, and never let water stand in the neck. Bulbs bought with red streaking already present should be cleaned before they are ever potted.
| Symptom | Likely cause | What to do now | Prevention |
|---|---|---|---|
| Red streaks on scales and stalk | Red blotch fungus | Peel affected scales, cut lesions, repot | Water at the rim, keep foliage dry |
| Bulb soft and brown at the base | Basal rot from standing water | Cut out to clean tissue or discard | Gritty potting mix, snug pot, empty saucers |
| White cottony fluff in the scales | Mealybugs | Swab with alcohol, repeat weekly | Inspect the neck at every watering |
| Leaves only, no stalk | Under-fed or no rest period | Nothing this season; feed all summer | Full sun, feed, eight-week dry rest |
| Stalk grows but buds abort | Cold draft or dry bulb | Move to steady 65F (18C), water evenly | Avoid cold windowsills at night |
| Notched, sticky leaves | Narcissus bulb fly larvae in bulb | Cut the bulb open and discard if hollow | Cover pots outdoors in early summer |
Rot: what it looks like and when to cut
Soft rot kills more amaryllis than everything else combined, and it is almost always self-inflicted through watering. It starts at the basal plate in a pot that stays wet, or in the crown when water is poured into the neck. The bulb gives under thumb pressure, the outer scales go brown and slimy rather than papery, there is a sour smell, and the leaves yellow and pull away far too easily.
A bulb caught early is usually saveable. Tip it out, wash the compost off, and cut away every brown or discolored part with a sterile blade until you are into firm white tissue. Do not be timid; a bulb reduced by a third that is entirely clean will recover, while one left with a brown patch to be safe will be mush within a month.
Let the cut surfaces dry in the air for twenty-four hours, dust them with sulfur or cinnamon, then repot into fresh gritty potting mix in a clean pot of the same size, with the top third of the bulb clear as usual. Water once lightly and then keep it almost dry until new roots and a shoot appear, which can take several weeks.
A bulb that has gone soft right through the basal plate, or that is hollow and stinking, is finished. Bin it rather than composting it, and do not reuse the compost for anything. If it was standing among other pots, check the neighbors by feel at the same time.
Never leave an amaryllis standing in a saucer of water or in a decorative pot without a drainage hole. More bulbs are lost to a forgotten inch of water in the bottom of a cachepot than to any pest.
Pests: mealybugs, mites and the bulb fly
Mealybugs are the main indoor pest and they exploit exactly the place you cannot see. They lodge between the outer scales at the neck of the bulb and in the tight fold where the leaves emerge, appearing as small white cottony blobs. Left alone they build into a colony that weakens the bulb and coats the leaves in sticky honeydew that turns black with sooty mold.
Deal with them by physical removal first. A cotton bud dipped in rubbing alcohol touched onto each insect kills it on contact, and repeating weekly for a month catches the ones that hatch afterwards. Peel back and discard any loose dry outer scale, which is where they hide. Insecticidal soap sprayed into the neck helps but does not reach deep into the scales, so it is a supplement rather than the treatment.
Red spider mite turns up on plants kept in hot dry indoor air, showing as fine speckling on the leaves and, when it is bad, a webbing across the leaf axils. Raising humidity and wiping both sides of the leaves with a damp cloth checks it. Thrips cause silvery streaks and distorted flowers, and are worth spotting because they get into buds before they open.
The narcissus bulb fly is the outdoor risk, and it matters for any amaryllis that summers outside. The adult lays at the neck of the bulb in early summer and the single fat grub eats the inside out, leaving a bulb that feels light and hollow and either fails to grow or produces a few thin grass-like leaves. There is no rescue for an infested bulb. Prevent it by covering the compost surface with grit or row cover over the laying period, and by keeping the pot rim in the ground rather than leaving the bulb neck exposed.
Handle the bulb and sap with care
Every part of an amaryllis is toxic if eaten. The bulb holds the highest concentration of the alkaloids responsible, and it is a genuine hazard to dogs and cats, which will chew a bulb left on a shelf or dig one out of a pot. Vomiting, drooling and diarrhoea are the usual result, and a large dose is more serious than that. Keep spare bulbs in a closed box rather than an open tray.
The sap can also irritate skin on prolonged contact, particularly when you are cutting a bulb into wedges for propagation or trimming out rot, which puts a lot of fresh sap on your hands. Wear gloves for those jobs, avoid touching your face, and wash afterwards.
Do not leave cut flower stalks or trimmed bulb pieces where a pet can reach them. The hollow stalk in particular is attractive to a chewing dog. Bag the waste rather than leaving it on the compost pile if pets have access.
Write down what happened and where
Note the date and the exact symptom whenever something goes wrong, along with which bulb it was, how long since it was repotted, and the compost you used. Red blotch in particular recurs on the same bulb over years, and a record of which bulbs have had it tells you which ones to keep isolated from the rest of the collection.
Record your watering as well: not every watering, but roughly how often, and where the pot was standing. Nearly every rot case traces back to a specific combination of a pot too large, a cachepot with no drainage, or a spell of cool weather when watering carried on unchanged. Writing down the position and the interval is what makes that connection visible next time.