I can comment on some mentioned above. Bachelor buttons will need support if tall. The taller variety of snapdragons will as well. Cosmos usually don't need support of any kind as they grow together and mass themselves and provide support to each other. Larkspur I have never grown and am not familiar with annual poppies but do have perennial poppies and they always need support of some kind if they are the tall variety. We have had many windy days and that will not help. Also, for many reasons, including the problem you are having, do not water your plants from overhead. Get a soaker attachment and water around the bases of them instead. If you don't want to stake every one, as long as they are not too spaced out, buy some of the plastic coated (metal) garden fence sections and piece together around plants to support them instead. Hope this helps.

Prolly the half day of sun, especially if there's been an unusual amount of cloud cover. Over-nitrification of soils can be a contributor as well. Perhaps last year's cosmos were a different cultivar?

Al

Another who says lack of sun is your problem.....and if I remember my time in Portland...even 1/2 day iof sun is less than 1/2 day in sunnier climes.
You are trying to grow annuals which need full sun in 1/2 sun..try other kinds of plants.

Linda c

I agree with what has been said already. However because I have a tendency to start plants too early and end up with starts overgrown and spindly when planted, which never become the good plants they should be, you may have done the same thing. Al

since you have lots of them ... cut some of them off at 6 inches... if you see rebudding in a few weeks.. start cutting more of them ...

experimentation is the key to knowledge.. and actually turning your thumb green ... have no fear ... i bet you cant make them look worse. ... and i bet you cant kill them ...

i know for a fact.. it will work on cornflowers... bachelor buttons....

you might be surprised how they rebud in a more compact form ...

not much different than how you prune mums from a single stem in spring.. to the bush you see in fall ...

its just a form of dead heading ...

too much fert.. as noted in an earlier post [Over-nitrification of soils] ... can also cause tall leggy green growth .... any chance they might be getting hit with lawn fert???

ken

Many tall annuals need staking. I haven't grown cosmos in a while, but I grow the rest and I stake them all once they start to flop. Also, because they are not in full sun, they will lean towards the sun, another reason to stake. I seldom fretilize; just add lots of compost from my compost pile.