Fall Mums and Asters

In this encore episode of Down the Garden Path, Joanne shares tips for choosing fall mums and asters.

Topics covered in this week's episode:

• Chrysanthemums, many horticultural varieties and cultivars exist including tender florist mums (a favourite of mine because of how long they stay blooming in a vase).
• Or Garden mums, more commonly known as fall mums.
• All Chrysanthemums are native to East Asia and Northeastern Europe. They became popular in North American gardening during the early to mid-20th century.
• Overall, fall or autumn gardening in the U.S. became particularly prominent in the 1950s and 1960s. Their popularity grew thanks to their vibrant colours of mums—ranging from deep reds and oranges to yellows and purples—this made them a popular choice for fall displays.
• Their ability to bloom late into the season and withstand cooler temperatures also contributed to their popularity in autumn gardening.
• Fall mums grown for our gardens are fertilized and pruned heavily to maintain their dense growth while in containers.
• It is possible to overwinter them in the garden but without regular maintenance, they can get quite large (tall and wide over a season or two).
• You often hear of gardeners or articles mentioning mid-summer to cut back or pinch back the foliage on garden mums that are being grown in the garden to slow down their growth and size.
• If growing in the garden, they benefit from mulching to protect them from the freeze and thaw most of us experience in our Ontario gardens or gardens in zones 4-6.
• They can be prone to spider mites and aphids as well as powdery mildew. Mildew especially if they are allowed to get large in the garden and then crowd with other plants and especially when there is high humidity and/or overhead watering.
• The downside of mums:
  • As a designer, my goal is to create gardens that are all season with something happening at all times and for there really not be a need for high-maintenance annuals. I do realize that there are times and places in the yard where one might want a pop of colour -- even me!
  • Potted mums perform much better in cooler temperatures. Unfortunately, garden centres seem to start selling them earlier and earlier each season.
  • They are thirsty plants when in pots, especially in the heat.
  • If the pots aren’t watered regularly they die very quickly and I think homeowners think they can revive them.
  • Once they have dried out, they are a throwaway plant. Don’t get me started on the plastic waste they generate!
• A better plant option for fall: asters!
  • There are 32 different species of aster in Ontario and over 100 species in North America.
  • There is a place for one in every garden or even a pot if you choose!
  • While some pollinators might visit garden mums for pollen that is where the benefit ends.
  • Asters not only supply pollen for honeybees and native bees, they also feed adult butterflies and we all want more of those in our gardens.
  • They are host plants or over 100 species of caterpillars, nature's bird feeders. Where there are caterpillars, there will be birds!
  • You may be lucky to find New England asters in pots at your big box store.
  • They are transplantable and will overwinter in the garden.
• In addition to the New England asters, there are several other native varieties that are sold in the perennial section of your garden centres.
• There is a variety of aster for every garden.
  • New England Asters Symphyotrichum novaeangliae: (purple, light purple) Full to part sun, blooms August to October, moist average soil.
  • Swamp Aster Symphyotrichum puniceum: (purple, light purple) Full to part sun, August to October, wet garden area
  • White Wood Eurybia divaricate: Part shade to full shade, September to October and will grow in a garden from moist to dry.
  • Heart Leaf Aster Symphyotrichum cordifolium: (lavender to light blue) Part shade to full shade, September to October, medium to dry soil
• Note: It is also recommended to pinch back or cut back asters in June to prevent them from getting too big and floppy.

Resources Mentioned in the Show:

Down the Garden Path: A Step-By-Step Guide to Your Ontario Garden

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Down the Garden Path Podcast

On Down The Garden Path, professional landscape designer Joanne Shaw discusses down-to-earth tips and advice for your plants, gardens and landscapes. As the owner of Down2Earth Landscape Design, Joanne Shaw has been designing beautiful gardens for homeowners east of Toronto for over a decade. She does her best to bring you interesting, relevant and useful topics to help you keep your garden as low-maintenance as possible. 

In Down the Garden Path: A Step-By-Step Guide to Your Ontario Garden, Joanne and fellow landscape designer Matthew Dressing distill their horticultural and design expertise and their combined experiences in helping others create and maintain thriving gardens into one easy-to-read monthly reference guide. Get your copy today on Amazon. 

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