Dendrobium with Dead Roots: Mini-Greenhouse Bag Method to Stimulate New Root Growth

Question:

Small Dendrobium ~2 years, flowered beautifully 3×. Never many roots; new canes thinner. Waited too long to change mix—almost all roots rotted 2 months ago. Trimmed dead roots, replaced mix, cut watering to encourage roots. No new roots/canes; canes getting skinnier, one leafless. Withheld fertilizer (suspected forced blooming), restarted weekly fert/water. Help? Resting period or sickness?

Answer:

Hi Catherine,

Smaller new canes indicated root problems (confirmed at repotting). Did you reuse the same pot? With few/no roots, always repot same size or smaller—media stays wet too long, rotting remaining roots.

Try this to encourage roots (spring = new growth cycle): warm shady spot, pot on saucer/tray, large plastic bag over plant+pot = mini-greenhouse. No water/feed 3 weeks; as it dries, may stimulate roots. After 3 weeks, add little water to tray, keep bag on. Repeat over 1–2 months.

Evergreen Dendrobiums: a few canes losing leaves over time is normal; many in short time is not. Semi-rest in winter—reduce water to barely moist, don't stop. Light feeder (~¼ label rate).

Follow-up: Catherine repotted in same pot (too small for reduced root ball). Bag method started; canes more shriveled, no roots yet—will continue month. Always used tiny fertilizer amounts, winter water only—glad that was right.

Follow-up Answer:

If no new roots soon, try this: remove from pot, clean media off roots, place with slightly damp paper towel in ziploc bag, seal. Similar to bag-over-pot but no pot. Should start growth cycle now—new roots + canes within month. Let roots reach ~2 inches, then pot.

You were doing right intuitively!

Jim Kawasaki
San Jose, CA