Rhododendrons for the North

Tue. Mar. 19, 2019

Click below to listen to my 2 min. Garden Bite radio show:  Rhododendrons for the North

In my latest Northern Gardener magazine is an article on rhododendrons!  AKA Rhodis. First question are rhodis the same as azaleas? Kinda. From the American Rhododendron Society comes this: All azaleas are rhododendrons but not all rhododendrons are azaleas. Azaleas have been reclassified and are now in the genus Rhododendron.

Azaleas at the MN Landscape Arboretum photo by Teri Knight

The University of MN has created the Northern Lights series of azaleas (which are also called rhodis!)

Azalea – Rhodi ‘Lemon Lights’ from Rare Find Nursery

There are no clear cut lines for distinguishing all azaleas from all rhododendrons but there are a few characteristics to look for.  Such as, true rhododendrons have 10 or more stamens which is 2 per lobe. Azaleas usually have 5 stamens or 1 per lobe. Azaleas have 5 lobes in a flower.  Click on the above link to the ARS for more information.  There are 2 types of rhododendrons,  Elepidotes are large leaved and Lepidote rhododendron have smaller leaves and are usually low growing or dwarfs.

Grows 5 ft. tall and 6 ft. wide

As for their needs:

  • Rhodis prefer morning sun and afternoon shade
  • a thick layer of humus on the soil protects their roots from drying out.  
  • they need rapid drainage 
  • a pH around 5, that means more acidic that most of us have.  You folks in Northern MN have a better shot at that pH naturally due to the granite structure in your area.   

You can do a simple soil test for pH.  Grab one at a local nursery or farm/garden store.  There are lots of choices out there.  If you do a full blown soil test, take it to a lab.  If you’re just doing the pH, any of them should work just fine.

These gorgeous shrubs need thoughtful planning and soil prep. With that, they’re long lived.  NOTE: these are slow growing plants

Rhodi ‘Purple Gem’ photo by Doreen Wynja – this darling grows to 2 ft tall and 3 ft wide

This LINK will take you to a wealth of information on planting and caring for your Rhodis and Azaleas!  Also be aware of the climate hardiness, they vary!

Rhodi’s for the Great Lakes Region. 

When planting, use a knife to cut through circling fibrous roots which can ball up in those containers. Pull the roots apart and spread them out. I’ll link you to the full article which has a ton more information.  

In the meantime, there are some stunning rhododendrons out there, including ‘Henry’s Red’,‘Purple Gem’, and ‘Bubblegum’. These links are provided for your information and aren’t an endorsement to buy from them.  Check locally first!  

Rhodi ‘Bubblegum’

Rhodi’s vary in height depending on whether they’re large-leaved or small-leaved but most make for a lovely specimen plant.  Buying locally is always your best bet for plant hardiness.  But that doesn’t mean you can’t try online sources!  

Look at the difference in color of this ‘Bubblegum’ from Scotland!

Rhodi ‘Bubblegum’ from Connon Nurseries in Scotland

Fall color varies on rhododendrons…

Rhodi Fall color at the Arnold Arb at Harvard University