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Azaleas - a beautiful addition to the garden

Marjory Blare, MD, Master Gardener

Azalea shrubs are a beautiful addition to the garden. The University of Minnesota developed a winter hardy azalea – ‘Northern Lights’ - which is now available in many different colors. In this article, you will learn how to care for azaleas, some of the lore about them, and why you will want them in your yard.

 Azaleas -  a beautiful addition to the garden

Azaleas make a wonderful splash of color in mid-spring! Azaleas are flowering shrubs in the Rhododendron family. All azaleas are rhododendrons but not all rhododendrons are azaleas. The key differences are bloom time, growth habit and appearance. The most popular azalea for Minnesota is the ‘Northern Lights’ azalea. It was developed at the University of Minnesota by Albert Johnson and was the first azalea to flower prolifically after minus 40° winters. Its introduction led to the development of many other colors after Albert Johnson’s death.

Azaleas need at least 4 hours of dappled sunlight, but in northern climates they can sometimes take almost full sun. It is extremely important that they have a soil pH of <5.5 that drains well. Fertilize in late winter or early spring. Azaleas bloom on last year’s growth so, the best time to prune is just after flowering. Azaleas need a sheltered area protected from icy winter winds, not a hot area next to the house. Don’t cultivate around azaleas because it will damage their shallow fibrous roots.

The Woodland-Azalea Garden at the UMN Landscape Arboretum features many of the Northern Lights series of azaleas. All over the MN Landscape Arboretum in general, you can see Albert Johnson’s original pink-flowered ‘Northern Lights’. The series is known the world-over for varied colors and flower-bud hardiness - an achievement that took two decades.

Historically, azaleas have been associated with various emotions and symbols. Generally, they are said to represent good qualities, such as:

  • Temperance – the Victorians often carried a bloom if they supported the prohibition of alcohol.

  • Emotional evenness.

  • Passion that is still developing and fragile.

Despite being overwhelmingly associated with positive qualities, Azaleas have a dark side as they are also associated with death threats-but only when sent in a black vase! This link may have occurred because in sufficient quantity, all parts of the plant are poisonous if ingested.

Azaleas are susceptible to some pests including: aphids, scale, thrips and Azalea sawflies. Azalea woes? Try University of Minnesota Extension’s publication: ‘What’s wrong with my plant?’ 

Check out this University of Minnesota Extension site for more information on, and to identify, Sawfly larvae. 

Pest Control:

  1. ‘Pick and Plunk’- picking sawfly larvae and plunking them into a bucket of soapy water.

  2. Squishing the insects - not for the squeamish.

  3. A strong jet of water.

  4. Insecticidal soap or horticultural oil.

  5. Azadirachtin and spinosad are effective for 1-2 weeks. Sawflies that feed on treated foliage are affected. These products have little impact on other insects.

  6. Residual pesticides include permethrin, bifenthrin, lambda cyhalothrin, and carbaryl and are most effective against young larvae. One application is usually sufficient. Follow the label instructions exactly and the timing must minimize contact with pollinators.

Note: Bacillus thuringiensis var. kurstaki (Btk) is specific to caterpillars and does NOT kill sawfly larvae.

These are some other hardy azaleas:

  • Roseshell Azalea, zones 3-8, 4’-8’ x 4’-8’ one of the parents of the Northern Lights series

  • Compact Korean Azalea, zones 4-8, 2-4’ x 2-4’ Lavender pink

  • Pinxterbloom Azalea, native to the eastern United States and hardy to zone 4. 

This is the perfect time to plan to add azaleas to your landscape! 

P.S. Don’t forget a soil test in the spring to help determine how to amend your soil!

Photo Credits:

Photo 1: (public domain)

Photos 2-7: Marjory Blare

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