Phlox is very susceptible to powdery mildew.

That sounds like way too much water. Plants do need water, but most of them don't like soggy soil. How much sun are the plants getting? Peonies (which won't bloom again until next spring) and roses like full sun, while some hydrangeas (which also bloom once a year) hate sun, while others tolerate and do well in it.

Stick your finger down into the soil near several different plants and see how wet or dry it is; if it's wet, let it dry for a couple days then check again.

Are all the plants newly planted? If they are, they are busy growing roots and not making flowers right now.

As rhizo says, phlox tends to get mildewed; it doesn't usually hurt the plant, it just looks messy.

I recommend that you guys get a hold of a good general gardening book - check the town library and see what they've got before shelling out a lot of money on one that won't help - and read up.

Try not to worry too much about the garden and how it's going to look when family gets there; they're going to be happy on your wedding day no matter what's blooming. Good luck!

I agree with the above :-) Deep watering twice a day is likely too much, regardless of weather conditions.

The phlox does have powdery mildew - a very common complaint with this plant. And the hydrangea and daisies (white flowers with yellow centers) have just completed their bloom cycle. The fact that your annuals are looking good should tell you that there is not much else wrong :-) And most annuals can tolerate more water than perennials - some even demand it.

You can deadhead to remove old flowers and tidy up the look of things but I agree that your wedding guests will have more important things to occupy them than the state or appearance of your garden!! And congratulations on your big day!!

I agree that you should check water levels in the soil, but if you've been having the same kind of heat and dryness we have, it may not be enough with a drip system. It depends on how much the emitters are putting out. Regardless, you need to change the schedule. Frequent, short stints of watering keeps the water near the surface, and so that's where the roots grow. Your plants will be healthier in the long run if you water for a longer period of time less frequently. In my established gardens I might run a sprinkler for 5 or 6 hours but only every 10 days to 3 weeks if there isn't enough rain, depending on the plants and soil. With newer plants, I'd water every 2-4 days for a longer time period so that the water can really sink in which will encourage deep roots and therefore more drought resisitant plants in the long run. How often depends on your soil type, weather (how much rain you've had and the temperature) and what your fingers tell you about soil moisture 3"-4" down. My soil is fairly well-drained, so if you have clay, what works for me would be really different for you.

For the mildew on the phlox, it won't hurt the plants' survival IME, but it can look homely. For now if you want you can remove the worse of the diseased leaves and put in the trash. In future years, if you prune out some of the stems to allow good air circulation, that may help. Be sure this fall to cut all the stems back to the ground and remove all the phlox leaves and put them in the trash (not a compost pile), since the disease spores overwinter in the plants' debris. If in future years they continue to look diseased, try replacing with a type that is known to be mildew resistant. Ask on the perennials forum about which types have been healthy for gardeners there. 'David' is one that comes to mind, but I know there are others.

For something like a wedding, I'd add more annuals if that is in the budget. A few good-looking pots, as big as you can afford, sprinkled around the garden will be fine, and cut the dead flowers off the perennials so they will provide a tidy green background. But as lisanti says you two are the focus, not the garden. Enjoy the day and the long-term blessings!

Edited to add: GG48 and I were writing at the same time, but she was a lot more succinct!

Thank you all so much for your advice and for the well wishes! I'm relieved to know that the plants may still be okay despite not flowering well. I will check the soil again - we tried to keep it moist but maybe that's where we are going wrong. Thank you all again, you've been very helpful!