What perennials to plant?



We had bought a corner lot home a few years back and did not realize that maintaining a lawn would incur so much of time and dedication.
I now plan to make a bed of colours in the middle of the lawn, but do not have any idea of what to plant, as I have not tried my hand in gardening before this.
I would prefer perennials that will flower every year and have some colours in bloom throughout the flowering season.
The size of bed which I have already started to prepare is 6 feet wide and 18 feet long. Your advice on what different kinds of plants to plant so that I have a contrast of colours in the yard most of the season. your advise on preparation of the flower bed would also be appreciated. I would prefer a contrast of colours and the height of not more that approximately 3 feet. The bed would be exposed to direct sunlight for the whole day.
Thank you for your advice. The most simple instructions and plants to choose would be very much appreciated.
The soil is mostly clay


Bed preparation is very important as it will determine how well your plants will eventually grow. A clay soil drains very slowly and lacks organic matter and a good soil structure which plants need to be healthy and reach their potential. It would be advisable to mix in a few inches of compost into your clay soil to break up the clay and help create a better soil structure so the roots have access to more air, nutrients and won’t be waterlogged. Most root zones of perennials need about 12 – 18″ so your garden must be dug to at least this depth. I have used the trench method where I dig down to the appropriate depth and to the width of a shovel/spade. This material then is shovelled out and placed in a location where I will dig the last trench. I then put compost into the bottem of the trench I have just dug out and begin a new trench behind the 1st one to the depth and width of your spade. The material from the second trench is then shovelled into the first, compost is added again to the bottem. Repeat this method throughout your garden to prepare the soil for planting. Then when each perennial is planted, I would also mix in more compost to the surrounding soil it will be planted in. Each year in the spring and fall approximately an inch of compost could also be added to the top of the soil which will eventually seep down into the soil profile on it’s own or with the help of earthworms and other critters in the soil.

Perennials for full sun could be:

Phlox paniculata – 3ft and various colours from white. purple to brilliant fuschia and red; Asters – various heights, white, purple, pink, rose; Rudbeckia ‘Goldsturm’ and other rudbeckia varieties- 2-3′, yellow; Perovskia – 2-3′, silver with purple flowers; Hemerocallis – 2′. many different colours available; Achillea – 1-2′, yellow, white, occasionally pink; Amsonia – 1-3′, light purple/white ball flowers; Baptisia – 3′, white or purple; Coreopsis – 3′, yellow, red; Echinacea – 1.5-3′, various colours from white, red, salmon, purple and more; Eryngium – 3′, silver purplish thistle flowers for interest; perennial Geranium – 1-3′, pinks; Heliopsis ‘Tuscan Sun’ – under 3′, yellow; Heuchera – 1-2′, darker leaf varieties require more sunshine and give colour and texture; Liatris – 2′, pink or white; Monarda – 2.5-3′, pinks, reds, purple; Sedums – 1 – 2′, Pink, brown, white blooms; Yucca – 2-3′, beautiful white bloom, great textural contrast, and Chelone – 2-3′, pink or white late flowering (If you have regular weekly irrigation). There are also many types of grasses that you could add to your garden to add more texture like little bluestem (Schizachyrium scoparium) or fountain grasses (Pennisetum). For very early flowering plants you might want to include bulbs of various types but they do prefer more well draining soil. If your soil is highly clay like now, I would wait until you have amended the soil with compost for  a couple years and then try adding crocuses, daffodils and tulips. They will extend your flowering season by 3 months in the spring.

Enjoy your new garden!