The rather late, wet start to spring this year and the recent hot, dry spell has taken its toll on many of our annuals. Some varieties are starting to look somewhat hard, instead of being soft and vegetative, and many annuals have stopped growing. Heat and water stress are the major causes of this hardness. Unfortunately, these stressed-out annuals can leave your garden looking a little blah at this time of year, which may be awkward when we have so many friends and relatives visiting. Late flowering summer annuals and perennials, however, can give your garden some needed colour. As I was walking through the gardens the other day, I couldn't help but notice how a few very special plants were doing more than their share to keep the colour going.
Yellow is always an important colour to give a lift to late summer gardens, and two excellent perennials immediately come to mind. The longest and strongest flowering variety has got to be the lacy leafed Coreopsis verticulata 'Zagreb'. It just never quits. Its cousin, the softer yellow C. 'Moonbeam', is also a non-stop flowering, more spreading variety. Both always look good without any care or attention and defy the concept of perennials needing a lot of work.
Terra Nova, a great breeding company in Oregon, has come out with a whole new series of very tender coreopsis varieties that are meant to replace fall mums. Available in nice new colours from 'Strawberry Lemon' and 'Mango Punch' to the bronze 'Little Penny', they are a delightful addition to summer and fall gardens.
My other favourite yellow perennial is a rudbeckia called 'Goldsturm'. This European introduction is just out of this world! It's hardy, relatively short (about 24 inches tall), and its large, single, yellow daisy-like flowers just keep on blooming right up until November. 'Goldsturm' is such an improvement over the other varieties - they're not even in the same league! A very vigorous and tall growing variety, called R. 'Herbstonne' is also truly amazing. Stretching up to six feet in height, this late summer giant creates an amazing display of colour from July to October. We have one at the entrance to our home, and it is spectacular.
Not to be outdone, annual rudbeckias really steal the show at this time of year. The low, larger flowered 'Becky' and smaller flowered 'Toto' series perform magnificently in our hot weather. For taller, more background plants, the 'Hirta' series, like the award winning 'Prairie Sun' and 'Denver Daisy', does the job nicely.
Helleniums truly provide some of the richest summer colours from bronze to burgundy, as well as terrific bicolours. There are many varieties, but H. 'Sahin' is a gold bronze bicolour that just never quits.
Echinaceas are also now in full bloom, and all the new colours from vibrant orange and golden yellow to white and hot pink provide a lasting perennial display. They also attract butterflies and honeybees.
Some other excellent late summer blooming perennials not to be forgotten are the pink-lavender blooms of Joe-pye Weed (Eupatorium 'Atropurpureum); the white, fragrant flowers of all the cimicifuga; and some of the new heliopsis varieties that make wonderful backdrops for perennial borders. Japanese anemones, too, are one of the amazing long flowering fall perennials.
In spite of the weather we may experience from year to year and how it impacts on our annuals, these perennials, and many more like them, are the workhorses of any garden and will add wonderful colour to a late summer garden.