None of mine flops. I have May Night, Caradonna and a couple others. If cut down way back after blooming, they'll give you another flush of bloom. That keeps them from flopping too. Maybe your soil is too rich.

If given enought sun they should stand erect.
Marcus doesn't flop or lean because its only 8 to 12 inch tall. Good for bordering.

Try to hide the flopping with a small branch or shrub branch. Anchor it in the ground and prop up to the plant.
It will disappear as it blooms.

Also shear May Night a few times before it blooms to incourage it to bush. Hope this helped.

My May Night has never flopped either. In fact, it's still going strong six years after I originally planted it.

I've got May Night, Purple Rain, and Blue Queen in full sun; all nice and upright, no flopping.

Try Indigo Spires salvia - it is great! One of my neighbors has one that is two years old and I think it would qualify as a shrub now. Its at least 4 feet tall - and does not flop over at all....Texas weather has been WEIRD this year and if it has not flopped over yet, I don't think that it ever will...

Here is a link that might be useful: Indigo Spires

Perhaps you have it somewhere it doesn't like. Maybe too much water, fertilizer, not enough sun. May Night, Blue Hills, Marcus have never flopped here. They spread but stay very upright.

I grow East Friesland, and it flops where I'm giving it more water than it really needs. I also had a clump I cut way back a month ago (I didn't like its purple competing with the adjacent purple penstemon while it was in bloom). It has grown back shorter and fuller and it's every bit full of blooms as it was when I cut it back. Very versatile, these plants!

Yes, they prefer poor soil and low moisture....

I know Salvia farinacea, Victoria would not be hardy for you, but it's hard to beat for easy, long blooming gorgeous blue flowering. I buy them in six packs as early in the spring as they are available and immediately pot them up into gallon pots. Water, fertilize (move them inside if a late HARD freeze is predicted), and by the time I'm ready for them to go into the ground replacing pansies, they are full sized and blooming, never to quit until fall freeze.

Also, Mystic Spires salvia is WONDERFUL if you want something a bit larger (2 to 3 feet). It's a hybrid between farinacea and Indigo spires with the best characteristics of both for my money.

I have an absolutely amazing salvia - sclarea v turkestanica that has fuzzy large leaves and amazing white flowers with pale purple or blue bracts. Grows to 40" tall, starts off singular but loves to seed around after the first blooming. The fuzzy leaves, the tall 6"-8" flower spikes.... guaranteed to be the show-stopper in your garden for years to come.