As promised earlier, I am posting a few of the types of plants that can be planted in Zone 5 that will normally go long periods of no rain without you having to water them. Remember to ask your greenhouse if this particular type will work for you. For instance one type of Hosta may not be drought resistant. So please check with the professionals. There are many other drought resistant plants out there. I am one of the many people out there who prefer to plant as many perennials (plants that come up year after year) as possible. Annuals can be purchased for flower planters, etc.
Thuja Green Giant Trees
Thuja Emerald Trees
Varieties of each of the following:
Geranium Ground Covers
Some colorful groundcovers
If you want to see what any of these look like, look them up on the internet. A lot of times when you do that, a list of other plants with similar water needs will appear. They usually look really good planted together.
I hope that this will help you.