One of my seasoned colleagues told me "build a palette"---select a few plants you like for sun, a few for shade, a few for dry areas, and a few for wet. Work with those for a while and get to know them like the back of your hand. Then maybe you can add a few more to your repertoire. This was the best advice I was ever given.
In Wisconsin, tough is essential. Cold hardiness is key to success. There's nothing more unpleasant to a client than to lose most of her new (and in some cases, pricey) plants over the winter and have to start over the following spring. In my area, soil is heavy clay---great for throwing pottery, but difficult for getting plants to establish healthy roots. And then there's the inevitable summer drought, heat, and humidity. Dead plants have a way of putting people off. And according to the Japanese, they eminate negative energy...
Since we have a short growing season here, it makes sense that one would try to select plants that will give a lot of bang for their buck. I tend to choose cultivars that bloom for unusually long periods, like over the course of several months. This eliminates the need for complex designs and garden clutter. Sure you can stage blooming throughout the season and create layers of plantings. But why not choose plants that will keep going and going, giving of themselves and asking little in return?
My top ten "old reliables" for SE WI:
10) 'Northwind' Switchgrass (Panicum virgatum 'Northwind'):

Great warm season grass that holds its form through fall and winter. Upright, vase-shape with blue-green foliage and delicate late summer seedheads. Butter yellow fall color that resembles a sheaf of wheat. I use this in mixed plantings, at the back of the border. Best when planted in groups of three or more.
Height: 4-5' Spread: 2-3' Light: Full sun Zone: 2
Photo courtesy of Meadowbrook Nursery
9) Reblooming Dwarf Daylilies (Hemerocallis cultivars): Yes, they are somewhat ub

Height: 12-20" Spread: 16-24" Light: Full sun (for prolific flowering) Zone: 4-5 Photo courtesy of Copper Leaf.
8) Shrub roses (Rosa cultivars): I say 'roses' in a sales consultation, and some clients bristle. Forget your grandma's tea roses---shrub roses are something completely different. My selections require little if any maintenance, bloom like crazy from early summer through fall, and are generally tough as nails. Now that being said---you will probably see some dieback every spring. No problem. The dead parts of the sh

Height: 2-3' Spread:2-3' Light: Full Sun Zone: 4-5
Photo courtesy of Easy Elegance Roses
7) Willow Bluestar Amsonia (Amsonia tabernaemontana):

A former colleague turned me on to this plant---it made an appearance in almost all of her designs (thanks, Carrie! I get it now.). This is unusual blue perennial blooms in late spring and early summer, and makes a comeback in fall with yellow-orange, fine-textured foliage. I love this at the middle or rear of a border, planted en masse and allowed to spread out. Try Amsonia with a contrasting, large-foliage plant in front of it.
Height: 2-3' Spread: 3' Light: Sun-Part Sun Zone: 3
Photo courtesy of White Flower Farms.
6) Hosta varieties (Hosta cultivars): Use Hosta to brighten shady spots, combine with more delicate perennials for textural contrast, or plant them in pockets and corners of your yard that require little maintenance. I am crazy for Hostas, all varieties, big and little, blue, yellow,

Height: 6 inches-3 feet Spread: 12 inches-3 feet Light: Part sun-Full shade Zone: 3
Photo courtesy of Song Sparrow Farm and Nursery.
5) Prairie Dropseed (Sporobolus heterolepis): Low-growing, native WI grass with fine textured foliage. Delicate seedheads appear to float atop arching stems in late summer and early fall. I

Height: 2-3' Spread: 2-3' Light: Full Sun Zone: 3
Photo courtesy of GardenStew.com
Next blog: Top ten landscape plants (#4 to 1)!