Hello all--

We have a crop of prestige that is exhibiting "flagging," i.e, the leaves on a single stem are wilting, with the rest of the plant unaffected.

There are no obvious signs of pathology or insect damage either internally or externally. The vascular system in the affected stems appears to be normal.

At this point the problem appears to be physiological in nature. Any ideas??

Thanks in advance // Randy

Randy,
"Flagging" as you term it can be found on certain Poinsettia crops where the junction of a side branch joins the main stem has become damaged and the vascular system no longer functions properly and the side branch shows wilt. The damage is usually on a lower branch that is growing horizontally where there is more weight and pressure on the joint and is exaserbated by someone who is heavy handed while watering or spraying the plants.
Upon visual observation the joint externally looks fine, the physical break is minute and not easily observed at the joint.
Poinsettias appear to be more prone to this malady when...
(1) Too many side branches are left on the Poinsettias and the lower branches looking for light grow in a more horizontal position which puts too much pressure on the joint.
(2) The Poinsettias were at some point spaced too close together causing weak side branches.
(3) Not enough calcium was used in the feed program to produce robust, strong side branches.
I have observed crops where the grower only started adequate calcium feeding half way through the crop and ended up with plants that had large thick stems on the upper growth and thin spindly growth near the main stem. This caused top heavy plants more prone to breakage.
(4) Poinsettias were pinched too early or allowed to grow too tall adding weight on the side branch joint.
There may be other reasons for this problem but these have been my observations over the years...
Michael Pawelek-Pecan Hill Nursery

This message has been edited. Last edited by: Michael Pawelek,

Michael--

Thanks for the nice detailed reply. Everything you say makes sense, and over the years I have seen much of what you describe. But in this case, many of the wilting branches are robust and upright.

Aditional info: Here in So. Cal, we have periodic hot, dry winds (Santa Anas) that will cause a temp rise of 15-20 degrees above normal. Points get really cranky when this happens, and will often develop wilted and dessicated leaves. I've never seen whole stems go down though.

We're do for another spate of Santa Anas tomorrow, I'll see if there's any correlation.

Thanks again for your response // Randy

Randy, Once a whole side branch starts to wilt while the rest of the plant looks normal I have never seen the wilted branch return to normal. The vascular system has been compromised and will not repair itself. You have to physically, and gently, remove the affected branch. I first noticed this "single stem wilt" on a crop of 6" many years ago where one section of Poinsettias had been pinched by one particular person who did not count properly and left 9-10 side branches. The bracts on Prestige can get so large I only leave 4-5 sidebranches on a 6" plant and sometimes that is too much.
..Michael Pawelek

This message has been edited. Last edited by: Michael Pawelek,

RJay -

What you are describing sounds like a classic case of stem breakage, though this is typically not a problem for Prestige because of its thick stems and upright branches.

However, there are several factors that can contribute to stem breakage. Those factors include:
- Low light levels during the vegetative phase between pinch and flower initiation. Lateral shoots are weakened.
- Plants grown at the edge of the bench tend to have shoots that grow more horizontally in an attempt to intercept light. These stems are more prone to breakage.
- Pinching too high and resulting in excessive branch count. The plant simply produces too many stems and leaves for the plant to support and lower shoots lack sufficient light to grow strong and vertical.