Gadenin日本語Get the appThe year at a glance
A calathea has no real dormancy but it slows almost to a stop when the room drops below 61F (16C), and it will not recover from disturbance in that state. Repotting, dividing and any hard tidying belong in the warm half of the year, and the cold half is about keeping conditions stable.
| Season | Watering | Feeding | Main jobs |
|---|---|---|---|
| Spring | Every five to seven days | Half strength every three weeks once growth starts | Repot, divide, flush the pot, move it off the strengthening sun |
| Summer | Every three to five days | Half strength every two to three weeks | Check for mites weekly, keep humidity up, never let it dry |
| Autumn | Every seven to ten days | Stop by mid autumn | Move back towards the light, plan for the heating |
| Winter | Every ten to fourteen days | None | Humidifier on, tepid water, no repotting and no dividing |
The intervals assume a six to eight inch (15 to 20 cm) pot in an average room. Read them as a starting point and let the compost make the final decision every time.
Spring: the working season
As the room warms past 68F (20C) and new leaves start appearing, the plant can take disturbance and recover from it. This is the whole window for the jobs that need doing, and there is no reason to hurry them into early spring while the nights are still cold.
Start feeding only when you can see a new leaf coming, and at half the strength on the bottle. Calatheas are light feeders and are easily damaged by salt build up, which shows as, inevitably, brown leaf edges.
- Flush the pot Before you start feeding for the year, run water through the compost several times to wash out last year's salts. It takes ten minutes and prevents a season of edge browning.
- Repot or divide if it needs it Late spring, one pot size up, or divide a clump that has filled its pot. Doing this now gives the plant the whole warm season to re-root.
- Move it off the strengthening sun A south or west position that was harmless in winter starts scorching as the sun climbs. Add a sheer curtain or pull the plant back before you see the first bleached patch.
- Tidy the old leaves Cut off leaves that are more than half damaged, at the base of the stalk. It puts the plant's resources into the new growth instead.
Summer: watch the water and the mites
Growth is at its fastest and so is water use. A pot that went a week in spring may need water every three days in real heat, and a calathea that dries out completely once will carry the brown edges from it for the rest of the leaf's life.
This is also peak spider mite season indoors, especially in a room with air conditioning, which is warm, still and very dry. Turn a few leaves over and check the undersides every time you water. Finding them in the first week is a fortnight's work; finding them in the fourth week can cost you the plant.
Do not stand a calathea outside for the summer. It gains little, and it comes back with sun damage, wind torn leaves and usually mites.
Autumn: prepare before the heating comes on
The autumn mistakes are both mistakes of timing. Watering on a summer interval into a cooling room keeps the compost wet and starts root rot. And leaving the plant where it stands when the heating comes on puts it in a dry blast it was never in before.
Work out now where the heat and the draft will come from, and move the plant before the first cold night rather than after the first damaged leaf. At the same time bring it back towards the window, because the position that was right in summer is too dark by mid autumn.
- Stretch the watering interval gradually Add two or three days at a time as the room cools, rather than switching to a winter interval in one step. Keep checking the compost with a finger.
- Stop feeding Stop by mid autumn. Fertilizer that goes in as growth slows is not taken up and stays in the compost over winter, where it damages roots.
- Set up the humidifier now Have it running from the day the heating comes on. Waiting until you see crisp edges means you are already a month late.
- Check for pests before the doors close Warm, closed rooms let a small mite population explode. Do a proper inspection of the leaf undersides at the start of the heating season.
Winter: hold it, do not grow it
The winter job is survival, not progress. Water rarely and always with tepid water in the morning. Do not feed, do not repot, do not divide, and do not respond to a stalled plant by doing something to it.
Keep it above 61F (16C) at night, which usually means moving it away from the window after dark or keeping it on the room side of a drawn curtain. And keep the humidity up: a heated room in winter can sit at 20 percent, which is drier than most deserts and the real reason winter leaves come out marked.
| Winter problem | What causes it | The fix |
|---|---|---|
| Crisp brown edges on every new leaf | Heated air at 20 to 30 percent humidity | Humidifier, grouped plants, move it off the draft |
| Leaves yellowing and dropping | Watering on a summer interval into cold compost | Stretch to ten to fourteen days, check the drainage |
| Blackened leaf margins overnight | Cold at the window | Move it into the room at night, above 61F (16C) |
| No new leaves for months | Normal at low light and low temperature | Nothing. Wait for spring and do not feed |
Build your own version of this calendar
The seasons above are a frame, and your room is the actual variable. A heated flat and an unheated house behave completely differently, and after one year of notes you will have a schedule that fits yours rather than a generic one.
Record four things and nothing more: the date of each watering and what you used, the date each new leaf unfurls and whether it opened clean, the date you moved the plant and where to, and the date you first see a pest. Next spring, read it back. You will know your real winter interval, how many leaves a good year produces, and which week the mites start, which is more useful than any advice written for an average room.
Take one photograph of the whole plant at the start of each season, from the same spot. Season to season change is invisible day to day and obvious in four photographs side by side.