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Good Lavenders for the North!

Lavender trials at the Chicago Botanical Garden.
Photo: Chicago Botanical Garden
Lavender is a favorite plant for many people, with its distinctive fragrance and attractive foliage. It’s a tough plant to grow in Minnesota. Although we have the alkaline soil lavender loves, it struggles in heavy clay and poorly drained conditions. Rarely, ok never listed as hardy in zone 4, lavender often dies in zone 5. Well-drained sites are essential and usually require consistent winter protection such as 2 feet of snow.

New research from the Chicago Botanic Garden’s Plant Trials, shows what was hardy in their USDA Zone 5 growing conditions, still warmer than most of Minnesota, but good information for us to know.
Lavandula angustifolia 'Imperial Gem'
Photo: The Royal Horticultural Society

Chicago Botanical Garden lavender trials

Richard Hawke selected 40 different kinds to trial for 7 years: 2010-2016.  Seven taxa received the highest ratings for exceptional flower production, healthy foliage, vigorous habits, adaptability to the growing conditions, and superior winter hardiness.

Based on cumulative evaluation scores, the top-rated lavenders in descending order were:
  1. ‘Imperial Gem’
  2. ‘Royal Velvet’ 
  3. ‘Munstead’ 
  4. ‘SuperBlue’ 
  5. ‘Jean Davis’ 
  6. ‘Niko’/Phenomenal  Phenomenal was the only top-performing non-angustifolia type. 
  7. ‘Sharon Roberts’.

Lavandula angustifolia 'Munstead'
Photo: Julie Weisenhorn, U of M
Look for these cultivars to grow in zone 4, plant early in the season to allow the maximum amount of time for establishment in well-drained sites.
Gardeners in the Anoka Sand Plain, this is a plant for you!

How to grow lavender

After seven years of trials, the gardeners at the Chicago Botanical Garden certainly know how to grow this plant! Here are their growing tips, so you can be successful, too: 
  • Lavenders prefer full sun and well-drained to dry, alkaline soils—gravelly or sandy soils are ideal.* 
  • Good soil drainage, especially in heavier clay soils, is crucial to year-round survival. 
  • Maintenance needs are few since lavenders do not require regular irrigation or fertilizer to flourish. Deadheading is the gardeners’ choice but is helpful in keeping plants tidy. 
  • Shearing lavenders by one-third after blooming removes spent flower stalks and shapes the plant. Substantial pruning may be necessary on severely winter-damaged plants; cut stems back after new growth begins in the spring. 
  • Potential diseases: fungal root rot can be troublesome in poorly drained soils and during periods of heavy rainfall and/or high humidity. Fungal and bacterial leaf spotting, stem blight, and wilt are also possible problems in warm, wet weather. 
  • Potential pests: Fourlined plant bugs, caterpillars, and northern knot nematodes are occasional pests. The natural oils in lavenders repel most grazing mammals such as deer and rabbits.
*Lavenders for Northern Gardens, Richard G. Hawke, Plant Evaluation Manager and Associate Scientist, Chicago Botanical Gardens. 2017

To see the entire lavender evaluation report, visit:  http://bit.ly/CBG_lavender_trials.

Author: Mary H. Meyer, Extension Horticulturist and Professor


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Comments

  1. Rabbits seem to like my perennial lavender. Early spring and end of summer they are partially chewed off.

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  2. Protect plants from animal browsing with 4 ft tall fencing like hardware cloth. Winters with deep snow require adding an extension to keep tall plants enclosed. More info can be found here: https://extension.umn.edu/planting-and-growing-guides/protecting-trees-and-shrubs-winter#put-up-physical-barriers-to-keep-animals-away-972411

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