Gadenin日本語Get the appThe shape of the hibiscus year
Almost every hibiscus problem comes from doing the right thing in the wrong season. The plant swings between two completely different states: a fast-growing, thirsty, hungry shrub through the warm months, and a nearly dormant houseplant through the cold ones. Water and feed suited to one are actively harmful in the other.
The turning points are set by temperature and light rather than by dates, which is convenient because it works the same wherever you garden. The plant goes outside when nights stay above about 50F (10C) and comes in before they drop back below that. Everything else follows from those two moves.
The big jobs are front-loaded into spring. Pruning and repotting both belong there, because that is when the plant can recover fastest and when there is still a whole season ahead for the regrowth to flower. Leave those jobs until summer and you spend the flowering season paying for them.
Autumn and winter are mostly about restraint. The instinct to keep feeding a plant that looks less happy indoors is the wrong one, and so is keeping the compost as wet as it was at the height of summer.
| Season | Main job | Water | Feed |
|---|---|---|---|
| Early spring | Prune, repot, start into growth | Sparing until new growth shows | None until shoots appear |
| Late spring | Harden off and move outdoors | Increasing with growth | Balanced feed, weekly |
| Summer | Flowering, pest checks, watering | Daily, twice in heat | High-potassium feed, every second watering |
| Early autumn | Wind down, tidy, check for pests | Reducing as growth slows | Stop by mid-autumn |
| Late autumn | Bring indoors before cold nights | Much less, let surface dry | None |
| Winter | Keep cool and bright, hold steady | Only when the top inch is dry | None, or a quarter-strength monthly |
Spring: the season that decides the summer
As light returns and the plant starts pushing new shoots indoors, do the structural work. Prune first, taking about a third off each main stem to an outward-facing bud, and repot if the plant has filled its pot or has been in the same compost for two years. Doing both in the same week is fine and gets the disturbance over with in one go.
Hold back on water until you see new growth. A plant that has been ticking over dry all winter has a reduced root system, and drenching it before the roots are active is the most common way to rot a hibiscus in spring. Increase watering as the shoots extend, not before.
Begin feeding only once the new shoots are clearly growing, with a balanced liquid feed rather than a flowering one, since this phase is about building the shoots that will carry the flowers later. Fresh compost from a repot carries enough for the first month, so wait that long if you have just potted up.
Then harden off. Once nights are reliably above about 50F (10C), give the plant a week in shade outdoors, a week in morning sun, and then its full summer position. Skipping this scorches the winter leaves badly enough that the plant sheds them and has to start again.
Summer: flowering, and keeping up with it
This is the season of daily work and it is mostly watering. A hibiscus in full sun and full growth will empty its pot in a day, sometimes half a day in a heatwave, and the price of missing one is a batch of dropped buds several days later. Check the compost every morning and water thoroughly whenever the top inch (2.5 cm) is dry.
Feed at every second or third watering with a high-potassium liquid feed once buds are forming. The plant is flowering continuously and the constant watering leaches nutrient straight out of the pot, so a heavy feeding schedule that would be excessive for most container plants is about right here.
Look under the leaf tips every week. Aphids on bud stalks and whitefly on new leaves both build fast in warm weather, and both cost you buds directly. Five minutes of inspection catches them while a rinse and one spray is still enough.
Resist the urge to prune. Light tidying and pinching of a few soft tips is fine, but any real cutting now removes the shoots that were about to flower. Save it for next spring.
Record the date the first flower opens and roughly how many flowers are open on a good week in midsummer. Comparing that number year to year is the clearest measure of whether your pruning, feeding and position are actually improving the plant.
Autumn: winding down without shocking the plant
As nights cool and growth slows, start reducing. Stop feeding around the middle of autumn, because late nitrogen produces soft growth that cannot harden and that will be the first thing whitefly find indoors. Cut back watering gradually in step with the slowing growth rather than all at once.
Bring the plant in before nights approach 50F (10C), not after. Waiting for the first genuinely cold night costs yellow leaves and a mass of dropped buds, and a plant chilled once takes weeks to settle. Move it in stages if you can, giving it a week in a sheltered spot on the way.
Inspect and treat before it crosses the threshold. Anything living on the plant outdoors, where predators and rain keep it in check, will breed unchecked in a warm room. Wash the leaf undersides down with a firm spray of water, deal with anything you find, and check again a week later.
Expect some leaf loss after the move regardless of how carefully you do it. Dropping a share of leaves in response to the drop in light is normal, and the plant is not dying. It will hold what it has once it has adjusted.
Winter: hold it steady and leave it alone
Indoors, put the plant in the brightest window you have and, if you can choose, a cool room rather than a warm one. Somewhere around 55 to 65F (13 to 18C) suits it well. A cool, bright plant rests properly, keeps its leaves and stays largely free of pests; a warm, dim one stretches into pale weak growth and breeds whitefly.
Water far less. Once the top inch (2.5 cm) of compost is dry, water moderately and let it drain fully. That may be once a week or once a fortnight depending on the room, which is a fraction of what the same plant needed in midsummer. Overwatering in winter is the single biggest killer of indoor hibiscus.
Keep it away from radiators, heating vents and the draft of an outside door. Hot dry air and cold blasts both cause leaf and bud drop, and a plant standing in the path of either will look worse every week no matter how well you water it.
Do not prune, do not repot, and do not feed beyond an occasional quarter-strength dose in a bright warm room. The plant cannot use any of it, and all three jobs are waiting for you in spring, when they will actually work.