Design a perennial flower bed for blooms spring to fall

Flowers blooming any time, spring to fall, bring beauty to your landscape design and improve curb appeal. To accentuate the landscape design, plant perennial flowers that bloom at varying times during the growing season so the flower bed is filled with continuous blooms. The flower bed shown above started with daffodils that were then followed by lily-of-the-valley. Before the lily-of-the-valley stopped blooming, the perennials were budding and bloomed through summer.
Choosing Plants
Click on this list of plants suitable for a sunny garden from North Carolina State University. The list includes some part shade flowers as well. Note the column for "Bloom Season." Shop your local garden center or online nurseries for more options. When shopping online, be sure to look for perennial flowers that are cold hardy in your USDA planting zone. 
Look for perennial flowers that appeal to you. The appeal may be the bloom color or shape, foliage, height or shortness of the plant, or its scent. Make three lists, one each for spring, summer and fall bloomers; or create the perennial flower list in software like Word or Excel where you can sort the columns by bloom season and plant height. For the column headings, write down:
  • ID
  • Flower Name
  • Bloom Color
  • Bloom Season
  • Height
  • Width 
“ID” can be a sequential letter (A, B, C…) or number (1, 2, 3…) for each flower so those numbers can be transferred to a garden drawing. You may not be using all the flowers you are listing, but by writing down all of your favorites, you will have a good base from which to choose when designing the garden.

Designing the garden
Measure the length and width of your garden. On a blank piece of paper or graph paper, create a scaled version of the garden, like perhaps 1/2 inch on paper could equal 1 foot of garden.
All the perennial flowers will start growing at about the same time; their bloom times and final height will occur at different times. Determine where you want the spring bloomers to appear. An option could be to have two to three spring bloomers like bergenia one-third of the way in from one side of the garden while a mass of bellflowers take up most of the right front of the bed. To the back could be daffodils and an area in the center could be creeping phlox.
Cut circles of paper to scale to equal the potential width of the plants you chose and write the ID number or letter to equate that plant (unless you have room to actually write out the plant’s name.) Place the cut-outs on your drawing. This approach makes it easier to move the pieces around as you finalize your drawing.

Alternatively, you could draw a circle in pencil directly on your garden drawing to equate the full width of each plant. To further qualify the seasonal bloom times on your garden drawing, try using colored paper for each season, like pink for spring, blue for summer and orange for fall, or use three different colored pens or pencils (like red, black and blue) when you write the ID on the cut-outs.
Continue this process choosing and placing summer bloomers and then fall bloomers onto your garden “map.” You may end up with more summer bloomers than spring or fall, and that’s fine particularly since there are so many summer blooming perennial flowers available. As you make your choices, consider the potential height of the flowers. You may need to swap out or relocate some flowers so tall flowers are closer to the center of the garden, or to the back if the garden is against a structure. Place shorter flowers to the front.
Planting time
Purchase and plant the perennial flowers based on your garden design map. Apply 2 to 3 inches of mulch, like wood chips or leaf mold, in the open areas around the flowers to help retain moisture and block weed growth.