Perennial Asters

There are many aster species but the ones most commonly used for cut flowers today are hybrids derived from Aster novi-belgii (New York aster) and Aster novae-angliae (New England aster). These are North American natives and you have probably seen their white or purple flowers in fields and along roadsides in autumn. While originating here in North America it is the English who really love perennial asters and all the well known cultivars were developed in England. Because their bloom coincides with Michaelmas, the Feast of St. Michael (September 29th), these asters are known in England as Michaelmas daisies. I'm a bit of an Anglophile and maybe that's why asters have always been one of my favourite flowers.

Red 'Crimson Brocade' asters with chrysanthemums.

Like chrysanthemums, late bloom and frost tolerance make perennial asters useful in the border and as cut flowers. Unlike warm coloured chrysanthemums, asters only come in cool colours - pinks, purples, blues, crimsons and white - with contrasting yellow or orange centres. If you are careless when combining chrysanthemums and asters, these colours can be a problem (think bronze and hot pink), but if you are a little careful, you can create smashing combinations like pale blue and yellow or bronze and dark purple.

Good filler flowers are always valuable and asters make especially nice fillers because of their range of color and season of bloom. In addition, the flowers are held atop multiply branched stems, so a single cut can yield a bouquet's worth of flowers. I sometimes create a bouquet by starting with a single big stem of asters and then filling in with other, larger flowers like lilies and dahlias.

New England Aster

Aster novae-angliae or New England asters are among the easiest to find and grow, but are less desirable as cut flowers because they close at night. This is not very noticeable outside but if cut and brought inside they may look like they are starting to shrivel and fade. Some of the better known tall New England varieties are the purple 'Hella Lacy', light pink 'Honeysong Pink' and dark pink 'September Ruby'. Monarch butterflies flock to 'Hella Lacy' so you might want to grow it for that reason alone.

New York Aster
Better as cut flowers are Aster novi-belgii or New York asters. They are tough perennials and make beautiful long lasting cut flowers but they are a bit more difficult to find and grow. The taller New York asters usually need to be staked. Fussy gardeners should also realise they are prone to powdery mildew and will usually drop the lower third of their leaves by the time they bloom. This doesn't really matter to me and I never bother to spray them with anything to prevent it. However, if growing them in a perennial border it is probably better to position them toward the back so this won't be noticed.

In The Gardener's Guide to Growing Asters (published in England, naturally) Paul Picton describes more than 280 novi-belgii cultivars. Of these, most of the commonly available ones like "Professor Anton Kippenberg' and 'Alert' are short. I've been able to locate only a few of the taller ones such as the fully double blue 'Marie Ballard', the dark red 'Crimson Brocade', and an unknown medium height lavender pink variety mistakenly sold to me as 'Fellowship'. I hope to add several others this year but they may not show up in bouquets for a year or two while I build up stock.

Other Asters
I also grow a hybrid aster called 'Little Carlow' with small 3/4" lavender-blue flowers. The plants are 3-4 feet tall so the flowers are the only little thing about 'Carlow'.

Lavender 'Little Carlow' asters with orange lilies and agastache.

Asters should be divided every few years, though the tougher ones will keep going even if you don't. Divide asters in the spring when the new shoots begin to appear. Experts recommend starting new clumps from individual new shoot taken from the outside of the old clump rather than splitting the old, woody center into pieces. I usually pot up the individual shoots in 3" pots and baby them along in a semi-shaded area for a few weeks before planting them back in a bed. I divide my New York asters every year and plant the divisions about 9"-12" apart. The new plants bloom at the usual time in the fall and a group of 6-8 can make quite show.

Cut asters when a third to a half of the flowers are open. The stems are woody and it is best to re-cut the stem under water when you get home.