Re: Rhododendrons

Tracy:  Thank you for your detailed report of soil conditions in Cornwall.  I 
found it fascinating.  

St. Louis is built over limestone bedrock, so soils here are alkaline and it 
is difficult to grow Rhododendrons at all. I live in Webster Groves, an older 
suburb which is a pocket of slightly more acidic soil created in part by a 
preponderance of oak trees growing for over 100 years in relatively 
undisturbed soil.  The unamended pH in my yard is 6.4.  That is just slightly 
acidic, but with diligent use of acid fertilizer it is enough to grow decent 
azaleas.  True Rhododendrons do not thrive and are short-lived, but azaleas 
are quite popular here. People from neighboring communities, where azaleas 
will not grow at all, drive through our town each spring to enjoy the 
display.  

I was quite proud of my own azeleas, some of which are more than 20 years old 
and nearly 5-feet tall, until a few years ago when I took a spring trip to 
Winterthur Gardens in Delaware and Longwood Gardens in Pennsylvania and 
realized just how magnificent they could be in proper soil conditions and 
reaffirmed by conviction to plant only native shrubs and trees.  

There is one species native to Missouri, Rhododendron roseum or wild azalea, 
which grows wild in Southeast Missouri, beginning just a few counties south 
of St. Louis, where acid soils overlay sandstone or igneous bedrock.  The 
flowers are very fragrant, showy, pink.  If I ever find it in the trade, I 
just might bend my rule a bit and see how it does in Webster Groves.  :Janis


In a message dated 1/7/00 10:25:35 AM Central Standard Time, 
steve.wilson@ukonline.co.uk writes:

> Dear Janis,
>  
>  pH is certainly the key to Rhodo success and I'm sorry that I took it for
>  granted. In Cornwall the pH varies, but is mostly neutral to acid, 
depending
>  upon where you are and whether the builders have messed it up. Our base 
rock
>  is mostly granite which generally gives an acid soil. I wouldn't say that
>  many places in Cornwall are acid enough to grow Blueberries without adding
>  additional peat to the soil, for example.
>  We also have quite a thin soil level in much of Cornwall, as the moorland
>  areas will testify, and the poorer, thinner soil also tends to be acid. 
That
>  combined with the climate makes for good Rhodo country. Often gardens with
>  neutral soil will grow Rhodos quite happily and Rhodo ponticum will grow
>  virtually anywhere, generally where you don't want it!
>  having said that we have poor soil, many of the valleys, where all the good
>  soil ends up, have almost tropical/rain forest like gardens with tree 
ferns,
>  bananas and hedychiums growing happily all year round. Whilst we haven't 
got
>  any mountains, we can certainly offer a wide range of growing conditions in
>  a small county.
>  
>  regards,
>  
>  Tracy Wilson, Cornwall. UK
>  
>  


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