Late summer fills the perennial sun garden with lots of yellow daisies. They dominate the landscape with the harsh gold-yellow of Rudbeckia 'Goldsturm' to the softer yellows of the much taller, 10 foot Silphiums. Solidago or goldenrod are also beginning to flower with their chartreuse to pure yellow sprays.

I like to blend blue flowering perennials in with all of the yellows, dotted among the almost countless forms of yellow composites. Favorites are many of the asters which spread their bloom time from August to October. Some of the earliest flowering types are the many New York Asters like 'Wood's Blue' or 'Woods Light Blue', both very compact only reaching a foot in height, just beginning to bloom.

The Michaelmas daisies include the assorted Aster frikartii types and their pale lavender-blue daisy flowers which bloom all summer into fall but are not always perennial. With their prolonged flowering period many people feel that Aster Frikartii is worth purchasing year to year if they don't return. They have been in flower for many months with no sign of letting up.

Two notable Aster species also send up stalks with beautiful blue daisies, the entire Aster oblongiflorus group which flower much later with blooms that open in October. Stiff stemmed, not prone to leaning or falling over, Aster oblongiflorus 'Raydon's Favorite' is indeed a favorite for anyone that owns it. Reaching 2 to 3 feet in height with countless blue daisies that never seem to tire, it flowers later than many, which makes it extra desirable.

A recent introduction, Aster o. 'October Skies' is more compact and I think will become very popular once discovered. Aster 'October Skies' flowers considerable earlier than A. 'Raydon's Favorite' but is a wonderful lavender blue. None of the Aster oblongiflorus suffer from powdery mildew or leaf spot, handsome from the ground - up. The foliage of this group is also aromatic and I often wonder if deer would find this unsuitable.

The species Aster spectabilis resembles Aster frikartii and may be considered a substitution if you find the prospect of replacing Aster frikartii every year an issue. The flowering time is much shortened though, and A. spectabilis will flower in early September with typical pale blue daisy flowers.

Other blue flowering perennials to consider are Perovskia or Russian sage and Salvia azurea, two lovely perennials that downplay the yellow glare of the late summer garden. Russian sage is generally very stiff in the full sun garden where the soil is not too rich. The stiff flower sprays bloom from late June to frost and can be repeatedly cut for flower arranging. The softness of the lavender-blue flowers spikes are a perfect foil for the more horizontal yellow daisies.

Salvia azurea on the other hand is very lax and is best planted as a weaver, allowed to meander between other perennials with long stems that lean here and there. The flowers are the most shocking blue, matched only by the clear blue skies of fall.