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The first thing that worries new hibiscus owners is that a flower opens in the morning, glows all day, and by the following morning has rolled itself into a soggy tube and dropped. Nothing is wrong. Individual hibiscus flowers are built to last a single day, occasionally two in cool weather, and the plant replaces them from a queue of buds sitting further down the same shoot. A healthy plant in summer is losing spent flowers and opening new ones on the same day, every day, for weeks.
Because of that, the number to watch is not how long a flower lasts but how many buds are in the pipeline. Run your eye along the newest six inches (15 cm) of each shoot. On a plant that is growing well you should see a bud in almost every leaf axil, at several different sizes, from pinhead to fat and coloring up. That staggered queue is what turns into continuous flowering. If the tips are producing leaves and no buds at all, the plant is telling you about light or feeding, not about flower life.
Deadheading is optional and does not make the next flower come sooner, because the next flower was already committed weeks ago. Pick the spent flowers off anyway if the plant is indoors, since they stick to leaves and to furniture and go moldy in still air. Do it by pinching the flower off just behind the swollen base and leaving the small green stub, which will drop by itself.
What does shorten the display is heat plus dry air. In a hot, dry spell a flower may look finished by mid-afternoon rather than evening. That is a water and humidity signal, not a fault in the plant, and it is one of the clearest cues that the pot is drying faster than you are refilling it.
| What you see | What it means | What to do |
|---|---|---|
| Flower opens and drops the next day | Normal flower life | Nothing |
| Flower finished by mid-afternoon | Heat and dry root zone | Water more often, move out of reflected heat |
| Buds form then yellow and drop unopened | A sudden change: move, draft or drying out | Fix the cause, hold the plant still |
| No buds at all on new shoots | Too little light or too little feed | More sun, start a regular liquid feed |
| Buds only at the very tips, none lower | Plant is stretching for light | Brighter position, prune in spring |
Bud drop: the plant reacting to a change, not a disease
Buds that swell to the size of a pea or larger, turn pale yellow at the join and fall off untouched are the classic hibiscus complaint. There is no pathogen involved in the great majority of cases. A tropical hibiscus aborts buds when its conditions change abruptly, because carrying buds is expensive and the plant will drop them before it drops leaves.
Three changes cause almost all of it. Moving the plant is first: bringing it indoors in autumn, taking it out in spring, or even turning it to face the room can shed a whole flush of buds within a week. Second is a draft, which means cold air from an open door, a window left ajar behind the plant, or the blast from a heating or air-conditioning vent. Third is drying out, even once, at the point when the buds are swelling fastest.
The fix is prevention rather than cure, since a dropped bud never comes back. When you have to move the plant, do it in stages over one to two weeks rather than in one step, and keep the light level as close to the old position as you can. Once it is settled, leave it alone. A hibiscus that stands in one place with steady water and light will hold its buds through to opening.
If buds drop and none of those three explanations fits, look underneath the leaves before assuming anything else. A heavy whitefly or aphid population feeding on the growing tips will also cause bud loss, and it is the one bud-drop cause that does need treating.
Write down the date you move the plant in or out, and the date buds start dropping. After one season the gap between the two is usually four to ten days, and seeing that gap in your own notes is what stops you blaming the wrong thing next year.
Summer water: more than feels reasonable
In full growth outdoors a hibiscus in a pot is one of the thirstiest container plants you will grow. It is a large, thin-leaved shrub in a small volume of compost, and in hot weather a plant in a ten-inch (25 cm) pot can empty that pot in a single day. Watering every second or third day, which is fine for most container shrubs, will give you wilting by midday and a steady trickle of dropped buds.
Judge it by weight and by finger rather than by schedule. Push a finger an inch (2.5 cm) into the compost in the morning; if it is dry at that depth, water until it runs freely from the drainage holes. In the hottest part of summer that will often mean once a day and sometimes twice, morning and late afternoon. In spring and autumn the same pot may go three or four days between waterings, so the routine has to follow the weather rather than the calendar.
Do not let the pot stand permanently in a full saucer. Hibiscus roots want to be wet and then drained, not sitting in water, and a saucer that never empties in cool weather is the fastest route to root rot and yellow leaves. In peak summer a saucer is useful as a buffer for a few hours; tip out what is left by evening.
One deep soak is worth several splashes. If the compost has dried to the point where water runs straight down the gap at the side of the pot, stand the whole pot in a bucket of water for twenty minutes until the bubbles stop, then let it drain. That rewets the root ball properly, which surface watering will not do once it has shrunk away from the sides.
Feeding hard in growth, and almost not at all in winter
A hibiscus flowering continuously is spending a lot, and in an open potting mix that is watered every day the feed washes straight out. Through the whole growing season, from the first strong new shoots in spring until growth slows in autumn, give a balanced liquid feed at every second or third watering, or use it at half strength every time you water, which is easier to remember and gentler on the roots.
Potassium is what supports flowering, so a feed sold for tomatoes or for flowering container plants suits a hibiscus well once it is in bud. Earlier in spring, when you want the plant to build the new shoots that will carry the flowers, a balanced feed with more nitrogen is the better choice. Alternating the two through the season works better than sticking to one.
Then stop. Once the plant is indoors for winter and the light is short, it can barely use what it is given, and unused fertilizer salts build up in the compost and burn the fine roots. Feed no more than once a month at quarter strength through the dark months, and in a dim room stop completely until the days lengthen.
Yellow leaves in the middle of the plant during summer, with green veins standing out against pale tissue, usually mean the feed has run out or the compost has been leached by constant watering rather than anything more exotic. Two feeds a week for a fortnight normally brings the color back on the new growth, though the old leaves stay pale.
Flush the pot once in midsummer by watering with about twice the pot's volume of plain water, letting it all run out. That washes accumulated fertilizer salts out of a compost that has been fed heavily for months.
The record that makes next year easier
Hibiscus problems are almost all about timing, and timing is exactly what memory gets wrong. Note four things each season and the plant becomes far easier to manage: the date you moved it outside and back in, the date the first flower opened, roughly how many buds were on the plant when you brought it in, and when you last repotted it.
The first-flower date is the most useful of the four. It tells you whether your spring pruning was early enough, since flowering follows the new growth by a fairly fixed number of weeks in your own conditions. If pruning late one year pushed first flower back by a month, you will see it plainly in two years of notes and you will prune earlier next time.
Note the position too, especially if you have more than one plant or move them around a patio. Which corner produced the most flowers is not obvious by memory at the end of a season, and it is the cheapest improvement available to you.