Gadenin日本語Get the appDiagnose from the symptom
Conebushes are fairly pest-resistant; what kills them is care. Brown leaf tips, dropping lower leaves and wilting shoots come from overwatering, phosphorus fertilizer or roots damaged at repotting. Because the remedies pull in opposite directions, narrow the cause using the weight of the pot and whatever you did most recently.
| Symptom | What you did recently | Likely cause |
|---|---|---|
| Leaf margins and tips brown | Fertilized | Phosphorus burn |
| Wilting in wet mix, lower leaves drop | Left it in rain, watered daily | Root rot |
| Whole plant weak after repotting | Broke up the root ball | Root damage |
| Pale stippling on leaves | Dry air indoors or under cover | Spider mites |
| White or brown bumps on stems, sticky leaves | Dense, crowded growth | Scale insects |
| Curled new shoots covered in insects | Spring or fall flush | Aphids |
Root rot: stop watering and wait
This is the most common way to lose one. Weeks of rain, a saucer full of water or a heavy mix suffocate the roots and the lower leaves yellow and drop. Because the plant is drought tolerant, reading the wilt as thirst and adding water makes it collapse fast. If the pot is heavy and the mix is wet under a wilting plant, think rot.
- Move it to dry shade Get it under cover in an airy, shaded spot and stop watering. Remove any saucer.
- Dry the mix Wait until the pot feels light. If it is slow, tilt the pot to drain the base and raise it on feet for airflow underneath.
- Do not repot You will want to look at the roots. Breaking up the root ball kills the healthy roots that remain. Cut dead stems only and judge recovery by new growth in spring.
- Fix mix and position next year Once it recovers, repot into a kanuma-and-pumice mix at the next opportunity and plan to move it under cover before the rains.
Phosphorus burn: flush it out
Days to weeks after a dose of ordinary granular or liquid fertilizer, bone meal or manure, the leaf tips and margins brown, new growth stalls and whole leaves turn brown and drop. Protea-family roots take up phosphorus without limit, so amounts harmless to other plants injure this one. If you remember feeding, suspect this first.
- Remove what you can Pick granules off the surface. Fertilizer mixed into the soil cannot be removed, so flush it as described next.
- Flush with water Water heavily until it pours from the drainage holes and repeat two or three times a few days apart. Keep the plant in bright shade out of the rain meanwhile.
- Stop feeding Nothing until new shoots appear. After recovery, if you feed at all, use a trace of a phosphorus-free protea fertilizer.
Brown tips: burn, scorch, wind or drought?
Brown leaf tips also come from hot afternoon sun, dry winter wind and severe drought. Sun scorch bleaches then browns only the leaves facing the sun; fertilizer burn browns tips evenly across the whole plant. The fix differs, so note which side of the plant went first.
| Appearance | Cause | Remedy |
|---|---|---|
| Sun-facing leaves bleach then brown | Afternoon sun scorch | Shade the afternoon side; move east-facing |
| Tips brown evenly on all sides | Phosphorus burn | Remove fertilizer and flush |
| Windward tips dry and brown | Cold, dry winter wind | Pull against a wall or under an eave |
| Leaves curl, plant wilts, pot is light | Drought | Soak in the morning |
Scale, spider mites and aphids
Insects are few, but scale settles on crowded, airless stems, spider mites thrive in the dry air under an eave or indoors, and aphids cluster on spring and fall flushes. All are easy if caught early, so look over the stem joints and leaf undersides once a week.
- Scrub off scale Brush white or brown bumps off stems and leaf bases with an old toothbrush. Cut out heavily infested stems; sprays do little against armored adults.
- Hose off spider mites At the first pale stippling, blast the undersides of the leaves with water. Mist the undersides regularly where the air is dry.
- Catch aphids early Wash or tape them off new shoots. Not fertilizing keeps growth firm and less attractive to them.
- Check for grubs at repotting Beetle larvae in the mix sometimes chew the roots. When you slide the plant out to pot up, look at the surface of the root ball and remove any you see, without breaking the ball apart.
Rules for nursing a weak plant
Whatever the cause, three well-meant moves make a struggling conebush worse: feeding it to perk it up, unpotting it to check the roots, and watering it more often. Correct the position and the watering interval, remove dead stems, and wait for new growth.
- No fertilizer Damaged roots tolerate phosphorus even less. Stop all feeding until new shoots are extending.
- No root disturbance Repotting or inspecting roots damages the healthy ones. Leave it in its pot and adjust only light and water.
- Water only when dry Wait for a light pot, soak, then wait again. A wilted plant in wet mix gets no water.
- Back into the sun once it sprouts New growth means recovery. Return it to full sun gradually and resume normal care. Note the cause and the fix for next year.