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Everything a dendrobium does is a season or more behind the conditions that caused it. The growth that appears in spring extends through summer, hardens in late summer, takes its cold dry signal through winter, and flowers from its nodes the following spring. A flowering failure this spring is almost always the result of something that happened last summer or last winter, and nothing done in the flowering season can repair it.
Once you can see the loop, care becomes a matter of not missing a handover. Push growth hard in spring and summer, drop the nitrogen in late summer so the cane hardens, give the winter the plant actually needs for its type, and leave the old canes alone throughout. The plant does the rest.
The table below is the whole year at a glance, written for the deciduous types because they are the ones with a demanding schedule. Read the season names as descriptions of conditions rather than as months. Where the evergreen types differ, the difference is noted in the last column.
| Season | Position and water | Feed | Main job, and how evergreens differ |
|---|---|---|---|
| Late winter, buds swelling on bare canes | Bright and cool indoors, start light watering | None yet | Resume water only once buds show. Evergreens have been watered all along |
| Early spring, in flower | Bright, cool, steady, moderate water | None while in flower | Keep it still and away from radiators and ripening fruit |
| Spring, after flowering | Bright indoors, water freely as growth starts | Balanced feed at quarter strength every second watering | Cut spent flower stalks only. Repot now if the mix has failed |
| Late spring, nights above 55F (13C) | Move outdoors over two to three weeks, water freely | Balanced feed every second watering | Harden off in stages so the leaves do not scorch |
| Summer | Outdoors, morning sun and afternoon shade, water every two to four days | Balanced feed every second watering | Build the new cane, stake it, inspect weekly for pests |
| Late summer, cane finishing | Outdoors in full light as the sun weakens, still generous water | Switch to low nitrogen and high potassium | Harden the cane. Same for both types |
| Early autumn | Stay outside for cold nights, taper the water | Stop feeding | Deciduous take the chill. Evergreens come indoors before 60F (15C) nights |
| Late autumn, frost forecast | Coolest bright frost-free room, no water once leaves fall | None | The rest begins. Evergreens go somewhere warm and keep being watered |
| Winter | 45F to 55F (7C to 13C), full light, no water at all | None | Six to ten weeks dry. Evergreens water every 10 to 14 days above 60F (15C) |
Spring: flowers, then the reset
Buds break from the nodes along the bare canes in late winter or early spring, and that is your signal to start watering again, lightly at first and then normally as they extend. Keep the plant cool and bright while the buds fill, and once they are swelling stop moving it. Warm dry air, a change of room, or a pot allowed to go bone dry at this stage causes buds to yellow and drop.
When the flowers are over, cut off only the short flower stalks where they join the cane, and leave the cane itself. Many nodes further up the same cane can still flower the following spring, and cutting it back removes them along with the plant's stored reserves.
This is also the one good repotting window, and you should be reluctant to use it. If the bark is still chunky and water pours straight through, leave the plant alone however crowded the pot looks, because crowding is what makes it flower. If the mix is dark, fine and slow to drain, or the plant has climbed over the rim, do the job now while new growths at the base are just moving and before they have made roots.
New shoots appear at the base as the light strengthens. That is the signal to raise the watering and start feeding a balanced orchid fertilizer at about quarter strength at every second watering. A cane fed hard from the moment it starts is a cane with fat nodes, and node quality decides next spring's flowers.
Summer: build the cane
This is the only part of the year where the aim is simply to grow the plant as hard as possible: strong light, plenty of water, regular feeding, and air moving around it. Outdoors is where this happens properly, because outdoor light in open shade is several times brighter than the best indoor windowsill and it is light that decides cane thickness.
Watch leaf color as your running score. Stiff, upright, light yellow-green foliage means the light is right. Soft dark green means too little and the plant should move to a brighter place in stages. Dry, papery cream patches mean sunburn and need more shade at once. Support the new cane with a stake and soft ties before it leans, because a cane that flops kinks at the base and never straightens.
Inspect weekly while you water, turning a leaf over each time and peeling back a sheath now and then. Summer outdoors is when scale, mealybug and aphids arrive, and every one of them is easy to remove early and hard to remove late. Stand the pot on feet or a slab so slugs cannot come up through the drainage holes.
From midsummer, change the feed. Drop the nitrogen and move to a low-nitrogen, high-potassium formula for the last stretch. Nitrogen late in the season keeps the plant making soft leaf when it should be hardening, and a soft cane does not respond to the winter signal.
Autumn and winter: the part most people get wrong
The new cane finishes when a small leaf appears at its tip and it stops extending. On a deciduous plant, that is the start of the wind-down. Leave it outside through the chilly nights of early autumn, taper the watering over two or three weeks, and stop feeding. When the leaves yellow and fall, stop watering altogether and move the plant, before frost, into the coldest bright frost-free place you have.
Then do nothing for six to ten weeks. No water, no feed, no misting, nights of 45F to 55F (7C to 13C), full light on bare canes. Light lengthwise wrinkling is normal and expected. This period feels like neglect and it is the entire mechanism by which the plant flowers, because a node kept cold and dry becomes a bud while a node kept warm and wet becomes a plantlet.
Evergreen types need the opposite and must be separated from the deciduous ones in early autumn. Bring them indoors before nights drop below about 60F (15C), keep them in a warm bright place away from cold glass, and carry on watering every ten to fourteen days. A prolonged chill makes them drop leaves, stall and sometimes rot at the base.
Whichever type you have, leave the old bare canes on the plant. They are next spring's flowering wood and this winter's food store, and cutting them is the most common self-inflicted reason a dendrobium does not bloom.
Resume watering when the buds appear, not on a date. A plant that has had enough cold and enough dryness shows swelling nodes on its own, and nothing you do earlier will hurry it along.
The notes that make next year easier
A dendrobium cycle is too long to hold in your head, so keep a short annual record. Six entries are enough: the date the first new growth appeared, the date that growth stopped extending, the date you stopped watering, the lowest night temperature the plant actually experienced in winter, the date the first bud broke, and which canes flowered along with how old they were.
After two years those notes answer almost every question without guesswork. If no buds appear, compare the winters and you will usually find either the room never dropped below 60F (15C) or the plant was watered part way through the rest. If buds appear but flowers are few, look at the cane made the previous summer and the answer will be light or feeding.
The note about which canes flowered is the most valuable of all, because it settles the question of what to cut. Once you have written down two seasons of it, you will know for your own plant whether flowers come from last year's cane, from two and three year old wood, or from both, and you will never again be tempted to tidy away the bare sticks that were about to bloom.