Geum + verbena drooping

Hi. Both my geum and verbena bonariensis are falling over more than I expected. Is there anything I should be doing to prevent this, or am I worrying about nothing?

 

You could use supports for your plants to straighten them.

It will happen when one side of the plant gets more sunlight than the other side.
The side of the plant that gets less sun will grow faster than the side that gets more sun, so forcing the plant to bend over to try and get more sun on the shady side.
The other reason is that your soil may be too good for them.
Both will stay shorter and stronger if the soil is poor - which is the type of soil they grow in in their native environment.

One of my Verbena bon. is almost 7ft atm on well-manured soil.
It'll probably snap in strong winds.

 

If you have an alternative location away from the fence in full sun they will be more upright, for the reasons that @Pete8 has outlined above. Even in full sun I've found that some Geums can flop. Cutting off the flowering stems that do sprawl at the base and leaving the upright ones helps to improve the appearance and encourages more flower production.