Watering and Feeding Leucadendron: No Phosphorus, Dry Between Waterings, No Wet Summers

Watering through the year

Conebushes tolerate drought and resent wet feet. The rule is to water thoroughly once the surface has dried, until it drains from the holes, and then wait for it to dry again. Empty any saucer at once. That said, letting the pot go bone dry for long periods browns the leaf tips, so lean dry is not the same as no water.

How to tell when it is dry

The surface color lies: it can look dry while the root zone is still damp. Use three checks together: the weight of the pot, a chopstick pushed down the side, and the look of the leaves. Memorize the weight right after a deep watering so you have something to compare against.

1. Lift the pot Noticeably lighter than just after watering means dry. If it still feels heavy, wait.
2. Probe with a chopstick Slide a chopstick down the inside of the pot and pull it out. No damp film on the wood means it is time to water.
3. Read the leaves Leaves curl inward slightly and lose their firmness when dry. If the leaves wilt but the mix is still wet, that is root rot, and the answer is to stop watering.

Why phosphorus fertilizer kills it

Members of the protea family grow dense clusters of fine roots that scavenge the trace of phosphorus in poor soils. The system has no off switch: in phosphorus-rich soil it keeps pulling it in until roots and leaves are damaged. That is why a dose of ordinary fertilizer that would perk up most shrubs turns a conebush brown and kills it back.

Standard granular fertilizers, liquid feeds, bone meal, blood and bone, and manures all carry phosphorus and are off limits. So is the starter fertilizer in most bagged potting soils.

1. Read the three numbers The label lists nitrogen, phosphorus and potassium. If the middle number is anything but zero, do not use it.
2. If you feed, use a protea or native formula Only fertilizers sold for proteas or for Australian natives, with no phosphorus, are safe. Use half the labeled rate in spring and fall.
3. You can skip feeding entirely The plant is adapted to poor soil and grows for years in a pot with no fertilizer. Poor color is almost always light or wet soil, not hunger.

Getting through a hot, humid summer

What troubles a conebush in a monsoon-type climate is not heat but heat plus humidity. Weeks of rain keep the root zone airless, and then high temperatures finish the roots. A gardener in Japan who kept one in the ground noted that the rainy-season damp was more dangerous than winter frost. A pot can be moved, so move it before the rains arrive.

1. Under cover before the rainy season Shift it beneath an eave or to the inner side of a balcony where rain cannot reach but air moves. Airflow matters more than full sun now.
2. Shade from hot afternoon sun Intense late-day sun scorches leaves and overheats the pot. An east-facing spot or 30 percent shade cloth in the afternoon is enough.
3. Raise the pot off the floor A pot sitting on concrete heats up and drains poorly. Set it on feet or a slatted stand so air moves underneath.
4. Water fully dry, in the morning Evening watering leaves the mix wet through a hot night and invites rot. Check that the pot is light in the morning, then soak.

Winter watering and placement

Growth slows in cold weather and water use drops. Wait two or three days after the surface dries, water in the morning, and let the surface dry before night. This is also when the bracts color, so give it full sun and keep it out of frost and drying wind. Indoors, use a bright window away from heater drafts.

Browning leaves: finding the cause

Brown leaf tips, dropping lower leaves and wilting shoot tips call for opposite remedies depending on the cause. Underwatering and overwatering look alike, so always check the pot weight and the mix before acting. If you fertilized recently, suspect the fertilizer first.

In every case, resist unpotting a struggling plant to look at the roots. Every minute of root disturbance delays recovery.