What causes Dutch Irises to fail to bloom?

Question

For the last 2 years my dutch irises have been a beautiful Spring show. However, this year they have failed to bloom.

I would greatly appreciate any ideas as to what may have gone wrong.

Thanks, Marg

Answer 1

I read that from time to time you need to dig them out and split the bulbs as they have created daughter bulbs and all the energy is going into them instead of the flowering. I did it it this year and tripled my irises like that.

In addition to that if you heavy soil it is said to give the bulbs a break. IOW: dig them out and store them for a month or two maximum.

All that digging need to be done in Summer so that you can put them back into the soil in early autumn.

I read this in the French "Truffaut" (Gardening bible) and from How should I care for my Dutch Iris plants? (although the answer is addressing iris' based on rhizomes) and I don't have the complete experience myself as I'm currently in the middle of trying.

Answer 2

The term Dutch iris refers to a group of bulbous irises which is divided into three - Reticulata, Juno and Xiphium - the first to flower are the Reticulatas, and Xiphium are the last. All require well drained soil in a sunny spot, but the Reticulata group prefer alkaline soil, and flower better year on year if fed every 2 weeks with a liquid low nitrogen tomato fertiliser, immediately after flowering is over, and until the foliage dies down. This group produces those short (6 inch) flowers in late winter to early spring, so if that's the type you've got, follow the feeding regime next year - start it even if flowers don't arrive within a week of the time you'd normally expect them to.

The Juno group particularly detest wet and cold soil conditions and rot quite quickly, and some varieties must be put under shelter for winter - but with those, you wouldn't get leaves and no flowers if wet was the problem, they'd just disappear.