Flower drop probable causes:
1. Day temp too high >95F
2. Night temp too low <65F
3. Too much nitrogen fertilizer
4. Too much water
5. Low light levels (reduces fertility).
6. Very low humidity (reduces fertility)
7. Poor air circulation (air circulation contributes to pollination).
8. Lack of pollinating insects.
9. Size of pot
10. Too much mineral in feedwater.
11. Too much grower attention.
Ya know, no offense but that list doesn't really help anyone because it doesn't describe how to diagnose which "probable cause" might be causing it, that and I have a few problems with it...
Here is my revised list with some observations I picked up over the years.
Flower drop probable causes:
#1: Day temp too high >95F - Flowers can drop from excessive transpiration, that can happen at
85F.
possible diagnosis -
A: Excessive Transpiration (water loss): Flowers drop when still greenish, petals may be wilted, if present at all (aborted sets).
B: Pollen Sterility (due to excessive heat during flower development): Flowers go pink or yellowish and drop with stiff petals (not wilted), same as when no pollination occurs.
#2: Night temp too low <65F - I have never seen flowers drop because of the temps being too low, I have had plants load up at 40F though they were berry sized due to the low temps.
possible symptoms -
A: Dwarf or "berry" sized pods.
B: Stunted plant growth.
#3: Too much nitrogen fertilizer - I don't think "too much nitrogen fertilizer" really makes that much of a difference, sure there will be more vegetation but in Peppers "new growth = new flowers" and I have never seen a plant with lots of N not set fruit. Exceptions being, blocking uptake of other important minerals.
#4: Too much water - Too much water will cause root rot, causing the plant to wilt... When I have encountered this, the last thing that started dropping was usually the flowers, the leaves typically started dropping first.
possible diagnosis -
A: Plant wilting with moist soil: Flowers may or may not bloom, leaves eventually sustain damage and drop, typically before flowers.
possible symptoms -
A: Fruit drop
B: Leaf necrosis and subsequent loss
C: Unopened flowers dropping
#5: Low light levels (reduces fertility) - No problem with this one, probably the #1 reason other than Heat that causes flowers to drop,
it can be easily diagnosed by underdeveloped female parts (short pistil) or little to no pollen in stamens.
possible diagnosis -
A: Underdeveloped female parts: Flower pistil will be very short, set much lower than the tips of the Stamen.
B: Underdeveloped or sterile male parts: Flower's stamens will never really fill up with pollen and may take on an immature look the entire life of the flower (till it drops).
#6: Very low humidity (reduces fertility) - Not sure about this one, never experienced dry weather before.
#7: Poor air circulation (air circulation contributes to pollination) - Agree with this one. (only if everything else is fine)
possible symptoms -
A: Flowers turn pink or yellowish and drop with stiff petals (not wilted).
#8: Lack of pollinating insects - Agree with this one. (only if everything else is fine)
possible symptoms -
A: Flowers turn pink or yellowish and drop with stiff petals (not wilted).
#9: Size of pot - Only if the plant is root bound (crinkly leaves, stunted growth), otherwise it can load up in a yogurt cup!
possible symptoms -
A: Leaves are hard and crinkly
B: Leaves are abnormally small
C: New growth slows
D: Healthy looking leaves start dropping
E: Open and closed flowers drop with green stems and stiff petals (not wilted).
#10: Too much mineral in feedwater - This would cause wilting with moist soil, same as #4.
#11: Too much grower attention - Agree here too, this includes over fertilization (not just Nitrogen).
One other thing of note, high heat can damage
developing flowers and cause reduced setting later on...
Typically what happens is the flowers either:
A: Abort before blooming
B: Bloom too soon
C: Develop little or no pollen
D: Have underdeveloped female parts (like a dwarf pistil)
Low light levels or insufficient spectrum can cause the above to happen as well.
