I disagree with Ken on this one and most Extension services out there do as well. The amount of nutrients in compost and garden soil is trivial and certainly not enough to create unwanted prolific plant growth in fall. You can incorporate compost (or garden soil) into your beds at any time. Doing so in fall is actually ideal because it gives it time to improve the soil structure for next Spring's growth. The link below supports my opinion as do several others you can find online. The very small quantity of slow-release fertilizer in garden soils, which is again much less by volume (0.08-0.05-0.05) than the nutrient content of compost (typically 0.5-0.5-0.5). Even if you were to add a slow-release now, it would not cause rampant plant growth. If you think about it, nutrients are present in most soils all the time. If the mere presence of nutrients in the soil caused excessive plant growth at the wrong time, we would have plants putting on tons of new growth in fall even without new nutrients added. It is when you flood the plant with nutrients, specifically nitrogen in the form of urea (which often occurs with quick-release fertilizers) that you see the sudden onslaught of new growth in fall. I add a light amount of Hollytone (which the directions indicate) to my acid-loving evergreen shrubs in the fall because nutrients do not just produce new growth -- they (namely, phosphorus and potassium) also help the plant's roots prepare for winter, regulate plant cell water management, and improve the plant's ability to resist disease. Here is a link that might be useful: Compost Is Fine in Fall

It's generous of you to want to share seeds with other gardeners and there's little reason not to other than the fact that named cultivars will likely not come true from seed. If you want to harvest the seeds, you need to wait until the seedpods ripen/turn to a tan/brown color. As SunnyBorders mentioned, some cultivars are sterile so the seeds won't germinate but that can't be said of every type. I've grown tall phlox from traded seeds and have lots of plants growing in my various beds that I grew from seed. The only way to be sure you share 'true' cultivars with garden friends is to divided the plants.

it does take a while to get a tall phlox to expand like this but once it gets going yummmm I allow mine to self propergate by cutting spent flowers and tucking them into the middle of the stems as the leaves wilt I add a handfull or two of there garden soil with the leaves and tap it in to the base I then let the stems stand as is untill 2 inches of leaf is seen in springcreating new stems I then cut the old stems and dig it up and seperate it into sections of size of four or five each and return them with in division back into garden.. You can do this divison into a 2 quart pot as well. I would assume your method looks correct but a guess would be concidering rotting hormone as it is a step for cuttings on different own root growers from one single tall phlox I got 3 stalks taking two years years the following year I got 5 stems on the forth 3 more every year after I now get an avg 6 stem from three second generation talls in two different but close spots next spring I am going to say yummmmmmmmm I predict a total of 36 which will all get a 5 to 6 stalk split from the second generation stems and 6 from the inital one which will get split into 3 stalks good luck on your efforts on propergating that way

Had Phlox 'Minnie Pearl' (a P. maculata hybrid). Was planted in the same location and at the same time as a Flame Purple and a Flame Pink. The 'Minnie Pearl' lasted a couple of years and the Flame phlox are still going strong. Haven't found Phlox maculata cultivars as hardy/long-lived as those of P. paniculata. Think "dwarf", with respect to garden phlox, doesn't always mean the same thing to all gardeners. Still I'm currently especially appreciating (based largely on having numbers of each of the following, their hardiness and their showiness): 'Pina Colada' (white), 'Tequila Sunrise' (coralish red), 'Starfire' (red), Flame Coral, Flame Purple, 'Delilah' (reddish purple), 'Wendy House' (reddish purple), Nicky (purple) and a pink I originally got from a local horticultural society sale that I call "My Pink". Just a bit taller than these, I'd say 'Galmour Girl' (coralish red) is currently my favourite garden phlox. The straight stands of 'Glamour Girl' look (stately?). 'Bright Eyes' cuts the same (figure?). For me, the dwarfs can look a bit shrimpy, plus garden phlox show better at variable heights. This August 5: