Yellowing Leaves

peterpies

I'm getting yellowing leaves on my dahlias. One plant is extremely bad, with a few flower buds going bad before they open. Another couple of plants have only the odd spot.

Is this over watering or poor drainage and the roots rotting?

The plant with serious problems is at the end of the flower bed where water would run and collect in heavy rain.

Others are in a extremely large pot, which have good drainage and would be under watered if anything.

Bessie

peterpies add some pictures, for a better chance at analysis of the problem. With more pictures, there is a better confidence of the correct diagnosis.

Teddahlia

"poor drainage and the roots rotting." Dahlias need some dry time between waterings. Prevention works. Fixing after root rot has damaged roots may not have an easy cure.

peterpies

ok, so over watering is the problem?

Will just back off the watering from now on and learn for next year.

Watch them flip, too under watering stress....

peterpies

This plant is the worst, some bud was rotten before opening. It's still flowering,

peterpies

Some others plants have small yellow spots, just on one or two leaves at ground level,

Bessie

peterpies the leaf damage appears to be consistent with slug and/or snail damage, in my opinion.

peterpies

The holes I understand, but the yellowing seems strange.

Cosey

Most likely a fungus called leaf spot (alternaria alternate).

peterpies

Thanks for the replies.

I'm going with over watering for now, so will back off watering a touch.

I'll increase my slug and snail checks, as they are a problem for sure.

Doesn't look like 'leaf spot' too me, but I'm no expert.