I pinch mine in mid spring, unless the deer do it for me.

Yes, you can cut it back to generate a bushier, more floriferous plant. But timing is everything :-) Like any number of mid to late summer/early fall bloomers, garden phlox, Phlox paniculata, will benefit by the "Chelsea chop" or cutting back one third to one half the plant in midMay (the time of the Chelsea Flower Show). Any later and you risk delaying or reducing the flower display but cutting back in May will create a shorter, denser plant and with more flowering stems. Pinching works too but observe the same timing.

OK, thank you. Sounds like maybe I should just leave the plant as is, at least, for this year. This is in fact a brand new plant that I received by mail order. It came bare-root (arrived and was potted-up, by me, perhaps 6-8 weeks ago?), and actual flowers began to appear just a few days ago.

The only reason I would pinch back summer flowering garden phlox would be to make the plant bloom a couple of weeks later than it would normally.

Here is a pic of my phlox today, I think the variety is called Mt Fuji. This is the third year in this spot - it is so full and thick it almost looks like a hydrangea!! It has NOT been pinched.

I recommend pinching or cutting back by 1/3 in early summer.

Also, thin older plants that have multiple stems.to reduce crowding, increase air circulation and hopefully, control mildew.. Down on your knees or stool and take out weak or thin stems. If you've cut back they will be so floriferous you won't miss the removed stems.

Good clean up in fall & spring might reduce disease.

Finally, buy mildew resistant plants. There are enough now to have a nice collection without buying ones known to mildew. Dodo Hanbury Forbes and Bright Eyes are old but very good; Too tired to remember newer ones but check out MT Cuba and MOBOT for phlox trials. Place in Vermont, I believe, sells only phlox and would specifiy mildew resistance;

Bluestone catalogue has a good selection and descriptions.

I'll bet youre like the rest of us and will ignore some advice. Just don't waste too much time or money on phlox that grow gray and greasy a month into summer!

if your garden phlox is so thick that it requires thinning by removing stems it is past time to dig and divide your plant!

Not necessarily. especially if a variety is prone to mildew

It is okay to disagree! If you have enough air movement, you won't have powdery mildew. I have never had a problem ever with that here living on a hillside. My phlox are dug and divided every four or so years to rejuvenate and to plant them in new areas - the phlox in the picture above was my grandmother's, and she had it for many years before her death 20 plus years ago. I really don't have time to cut back anything in the garden, the phlox have never gotten that treatment here!

They really do best being divided and transplanted on a fairly regular basis from my experience, but then every one's conditions are different. What works for one gardener doesn't always work the same for another gardener with different conditions.