Hostas and Hydrangeas are in the same bed. Soil under the added humus is clay.
Yes, Ph of 5.8 to 6.8 on the neutral side is desirable.
Here are in growing and care requirements to refresh you.
I also have this combination in my MN garden! It's a pretty combination.
I have 2 in large pots and live in central Minnesota. Can I just put them in the garage and should I water them and cut them back?
Let the plants die back naturally.
When they have gone dormant you can dress the top of the pots with a layer of leaves or some hardwood mulch. This will help with moisture retention.
When they have gone dormant you can move them to the garage.
Check the pots once a month to make sure the soil has not completely dried out. You can add a small amount of moisture if needed.
The key to wintering is to make sure the temperature stays quite constant.
Not cold, then thawing.
I know deer will eat most anything but there are some things they seem to like more than others such as hosta, hydrangea, etc. I was wondering if they seem to especially like astilbe.
Deer will eat almost anything when there's a limited food supply, so it's possible they will eat astilbe if there isn't anything better on the menu. I can tell you from personal experience that rabbits seem to love astilbe. This article may help you if you have a large population of (hungry) deer in your area:
Looks like an Astilbe but is over 5 ft. tall. What is it? It also self propagates.
There are many varieties of Astilbe and they can vary from 2 to 5 feet in height.
Goats Beard does have a look similar to Astilbe.
Also Tree Sorbaric or Kashmir False Spirea could be possibilities.
Is planting an Astilbe under a Flowering Crab Tree ok?
Ground covers and spring bulbs work well too.
How to grow and care for astilbe plants outdoor or indoors?
Astilbe is an outdoor perennial plant.
Here is a link with planting and growing information.
I planted Astilbe in my shade garden late spring/early summer. I have tons of leaves and they are very tall (12" or more) but there are no blooms. They are kept moist due to the location; I hardly have to water them. I read now that compost should have been used to promote growth of the blooms. Is there anything I can do now to get some late summer blooms? I am in coastal VA.
You likely have high Nitrogen in the soil, which causes lots of lush greens but little flowering.
Phosphorous can be added and Bone Meal is a good way to do this.
Here is a few links for you.