Hartley Magazine

All the latest news, hints, tips and advice from our experts

Asters, Dahlias and Ventilating your Greenhouse

At the beginning of the month, I was privileged to give the annual Percy Picton Memorial lecture at Colwall gardening club, the timing was perfect for a visit to the Old Court Nursery and Picton Gardens, home to the National Collection of Asters. Ernest Ballard of Colwall near Malvern, a chemist in the family cider vinegar company was the first great British ‘Aster’ enthusiast, Percy followed on and now his son Paul, Britain’s current ‘Aster Master’ maintains the garden and nursery today. Ernest’s first great introduction was Aster novi-belgii ‘Beauty of Colwall’ with flowers of lilac-blue that remains a classic to this day. In 1907 when the RHS held a trial of over 300 Aster cultivars and this was the only one to gain a First Class Certificate. There are many Asters named after Ernest’s relatives one of the best is gorgeous lavender blue Aster x nova-belgii ‘Marie Ballard’ with double flower-heads up to 2” or more across. I bought mildew resistant Aster x frikartii ‘Monch’, one of the finest with clear violet-blue flowers from July to October and beyond, depending on the weather and popular mauve pink ‘Patricia Ballard’ that is robust and reliable reaching 3’ tall; Aster x novi-belgii ‘Percy Thrower with its large blue flowers caught my eye too. Asters prefer an open sunny site on moisture retentive, free draining soil. Add plenty of organic matter, like spent mushroom compost or well rotted organic matter to one spades depth before planting on sandy soils; improve clay with organic matter and grit. Keep them well watered and mulched so the foliage stays lush and green. The Picton garden contains some ‘Michaelmas daisy’ borders that were once a feature of Edwardian country houses. If you enjoy autumn gardens, I thoroughly recommend a visit (www.autumnmasters.co.uk).

Dahlias, the queens of flamboyance, have flounced in and out of fashion for decades and they too are ideal for bringing a blast of colour from late summer until the first frosts. Dahlias are over 95% water! Where winters are warm, many gardeners over-winter them in the ground, covered with a good layer of mulch to protect them from frost. However, it is safer to lift them immediately after the first frost, label the tubers and allow them to dry on a greenhouse bench, remove any that are diseased or damaged, dusting the cuts with sulphur then store them over winter in trays of multipurpose compost or boxes of anything from perlite to newspaper in a cool, frost free place. Check tubers regularly throughout the winter and remove any that are rotting and replant in spring the following year.

Remember to ventilate the greenhouse on warm days, clean and insulate with bubble wrap or fleece and check that your greenhouse heater is working before the first frosts. Rake up any infected leaves as they fall, particularly those with black spot, pear scab or powdery mildew and put them in the compost recycling bin. Any healthy leaves can be rotted down in a wire mesh frame supported by a timber stake at each corner and will make excellent soil conditioner for your borders. Happy Gardening!