Answer: For the detailed propagation information you want, I would suggest you research the individual plants. Web sites such as the Missouri Botanical Garden's Kemper Center will provide some information,
and Tom Clothier's web site will help with seed germination requirements,
and the following article discusses other methods.
Keep in mind that many plants can be propagated several ways, meaning by seed, by division and also by cutting so your choice may be dictated by the season you are in, and also how many plants you need, and whether or not you can accept the variations that result from growing by seed.
Most plants will tolerate a range of soil pH, if there is a distinct preference you may find it noted in the plant descriptions. However, a range of 5.5 to 6.5 should suit most.
As a general reference for gardeners in the northeast, you might like Dr Perry's Perennial Pages.
Daphne shrubs may show signs of decline due to fungal infection or pests such as aphids or scale. You might want to consult with your local county extension to see if they can help you determine the cause of it looking thin. Based on knowing the specific cause they recommend what steps to take. If a chemical control is needed they will ahve the most up to date information on what to use and how/when is best to use it for maximum results.
Tall border phlox can be thinned in the spring to promote air flow through the plant and thus reduce the chances of mildew developing on it, and if you also trim it back a bit in mid spring you can keep it a bit shorter. The trimming delays blooming however. If you want to experiment with that, try it on just one plant and see if you like the results.
I hope this answers your questions. If you have more questions, please try to limit it to one question per entry at the Q&A form. But, ask as many as you like!
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