Questions regarding dendrobium kingianum - Orchid Board

vbng · #1 05-26-2018, 04:15 AM

Hello everyone,

Please help me out here. I have 6 questions below regarding my newly bought dendrobium kingianum (from Australia) (image 1) and not sure if you can explain the root case and what should I do to help my plant. Thank you.

1) The white roots are all dried out underneath and so I cut them off leaving only 1 inch of roots behind but the roots are thin and brown like straw. (images 2)

2) There are some roots wrapping around the stems and not sure if they are still alive. (image 3)

3) There are some leaves turning yellow. (images 4 & 5)

4) There's a black dot sort of like burnt dot in one of the leaves. (image 6)

5) There's a leave with split ends. (image 7)

6) There are many tiny black dots on the stems and not sure if they are fungus. (images 8 & 9)

Thank you,
Vicky

estación seca · #2 05-26-2018, 04:24 PM

Don't ever cut off roots. You can't tell whether they are alive or dead.

The roots you cut off were alive, not dead. Orchid roots do not look like roots on other plants.

Now it can't take up enough water to support the leaves. It will drop most or all of the leaves. Everything you show in the photos is caused by the plant being unable to take up water, because it has no roots.

Now is growing season. It will probably begin making new shoots from the base. The new shoots will grow new roots, and the plant will probably survive.

vbng · #3 05-26-2018, 10:36 PM

Thank you for your reply Estación. How about those tiny black dots on the stems? Are they caused by fungus? Thank you.

estación seca · #4 05-27-2018, 09:02 AM

The brown dried sheaths on the pseudobulbs are dead, so there's no reason to worry about them. Lots of orchids have dried sheaths enveloping pseudobulbs. Some people peel them off. Others don't. I leave them on.

Regelian · #5 05-28-2018, 04:21 AM

OK, to be honest, you are worrying toooo much. Evergreen orchids tend to shed leaves when the new growths are starting. A normal occurance. Some yellowing or darkening of leaves on new aquisitions is normal, as the light conditions will be different from the previous. Small black/brown spots are not a worry. All plants may get them from misting (water spotting from light) and the occaisional fungi. As long as they are non-spreading, there is little to worry about. Do be careful of sunburn, due to strong light. D. kingianum can take full sun, if given time to adjust. The leaves and stems will redden with anthocyanin, a kind of sun protection device. I try to avoid this, as it is, also, showing me the limits for that particular orchid.

Roots are best checked for life by wetting them. If they do not show a bit of green, then they will generally be dead and only usefull for anchoring the plant. Dormant and live roots will show green in a few minutes (chlorophyll). This species can take a prolonged rest, when the roots look quite dead, until they get wet. As Estacion mentioned, just leave them. Unless they are actually rotting or in great surplus, they do no harm. This species is best in an open, hard substrate, such as coarse bark or lava (or both). The roots like air and drying is generally positive.

My plants often look a bit ragged after a Summer in the garden. Wind and insects will take their toll. They are, however, thriving and full of flowers in the Winter.
cheers, J-