Blending colors in perennial flower beds
Shrubs don't require much knowledge of colors. White or yellow variegation is available on many plants. Purple color is also common in landscape. Otherwise, woody ornamentals are mostly green. You might have a dark green or a light green but nothing like the array of flower and foliage colors you find in perennials.
Given this multitude of choices in perennial plants, how do you blend pleasing color combinations with annuals and perennials? You might experiment for years and find combinations that work. A famous English Gardener named Gertrude Jekyll did this (along with a lot of other serious gardening.) Another option would be to use the same flower combinations she used. The trouble is that this option would involve moving to that particular part of England since many of her combinations won't work very far away from that site. Finally, you can by use colors that help blend all the other colors you try.
The most common color used to blend other colors is silver or gray. Silver or gray colors normally come from dense hairs designed to shade the leaf surface from the sun. Silver gray plants include artemisia, gray santolina, dusty miller, rose campion, sage, yarrow and lambs ear.
I have been seeing a couple of different artemisias in landscapes around Cabarrus county so I decided to learn more about it. Artemisia is named after the Greek goddess of chastity. I guess it is a good thing she had a plant named after her since she doesn't get worshiped too much these days. There are actually eight different species of artemisia. They include French tarragon (Artemisia dracunculus) which is a culinary herb I have tried to grow in the past and White Mugwort (Artemisia lactifolia). 'Wort' means 'good for' so evidently somebody thought this plant was good for your mug. It is the only artemisia used for flowers. Neither of these is gray. Artemisia absinthium is the most common on used for gray foliage. Artemisa schmidtiana cultivars are also available locally. Both plants go by the common name wormwood. You can easily see the difference in the foliage when you buy the plant. Assuming you are not stupid enough to use them as a mind-blowing home remedy, the only other important difference between these two artemisias is the height. The first one grows about 30 inches and the other grows about 12 inches high. I have seen one other artemisia in local landscapes. I have tentatively identified it as Roman Wormwood (Artemisia pontica). It has a similar color but is invasive.
Dusty miller (Senico cineraria) is commonly grown as an annual. It is a perennial and where the temperatures don't go below 32 degrees it becomes a shrub. Some gardeners overwinter it but I have never had success overwintering it. I suspect a dry soil with a high organic matter content is the best for overwintering. This has become a favorite to mix in combination pots.
I prefer the name Lychnis coronaria over Rose campion. An individual plant doesn't live very long but it always seems to come up from seed. It has a vivid fluorescent magenta pink flower so it is fitting that it has a blending type of foliage.
Some yarrows (Achillea tomentosa and Achillea filipenulina) have woolly gray foliage. Coronation Gold is a well-known cultivar. They can add some gray and also beautiful blooms.
Santolina has both green and gray forms. I suspect this plant will never become really popular. It requires poor soil for best results and the people that try new plants also improve their soil. Other than providing poor soil, keep the plant pruned and prune the spent flowers. I have covered lamb's ear, and sage before. Some thistles have silvery, gray foliage but so far I haven't had the inclination to grow them. Also tree germander (Teucrium fruticans) has great gray foliage but you have to move it indoors every winter.
Article was written by David Goforth Agriculture Extension agent North Carolina Cooperative Extension Cabarrus County Center. Visit my homepage http://cabarrus.ces.ncsu.edu/ or http://cabarrus.ces.ncsu.edu/index.php?page=lawngarden or my blog http://gardeninggurugoforth.blogspot.com/
Contact me at David_Goforth@ncsu.edu. Reviewed 2007.