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 and 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 indeed, they don't return. They have been in flower for many months this summer, 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 a favorite, reaching 2 to 3 feet in height with countless blue daisies that never seem to tire. A recent introduction, Aster o. 'October Skies' is more compact and forms a loose mound rather than a stiffly upright shape. None of the A. oblongiflorus suffer from powdery mildew or leaf spot, handsome from the ground - up. The foliage of this group is also aromatic which is great for the gardener with deer problems, these two are completely ignored by grazing deer.

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. Drainage is essential to grow Russian sage well and they prefer a location where you do not use woodchip mulch, especially during the winter months.

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. This unusual salvia is handsome weaving through the upright stems of fall flowering boltonia or interplanted with Miscanthus 'Morning Light', with its fine white striped foliage. In both situations the salvia will dutifully weave itself in and out of upright foliage and eventually weight itself down with spectacular blue flowers.