Rhododendrons

Is this natural landscape? Amazing.

I think this was a planned garden but I have seen rhododendrons and mountain laurels growing along stream banks and rivers in the northeast US. There are a few pics on here from Pennsylvania of natural landscapes with rhododendrons and mountain laurels. They are very beautiful and can get huge too!

Yes, I have seen them. Beautiful. I am just curious, if they are natural there or were planted there. There was found rhododendron here in high mountains and somebody said that it is not natural there and must have been planted, although I know rhododendrons love forests climate.
I love them, as they are evergreens and can create wonderful colour exhibition in April and May without a lot of work around them. I love namely Mrs Lewinski and Blue Monarch, both have in my garden. By the way, if I may ask here, what does it mean if one of them started to have light green-yellow edges on leaves? Otherwise leaves are shiny and without any other alterations.

Most likely the yellow-green is due to iron deficiency, pretty common in rhododendrons and any other acid loving plant (evergreens especially). I use holly tone fertilizer (or any fertilizer for acid loving plants). If that isn't enough you can get Iron from a garden center.
Also helps to make sure they are in acidic soil. I use a 50-50 mix of sand and peat moss for rhododendrons and mountain laurels, they love it :).
I've always known them to be woodland/mountain plants. There are some places where rhododendrons cover entire hillsides. Wouldn't surprise me if they are native growing there.

OK. Thank you. How often do you put this mix directly to the roots? Just when you plant it or regularly? I read in garden magazines, that rhododendrons should be each spring taken out from the soil, their "nest" renewed by peat and kompost (1:1) and then replanted. I do it with all my rhododendrons, which bloom perfectly and are healthy, but Mrs Lowinski has grown very fast and is already a big shrub for me to re-plant it annualy. So last year I just piled a lot of peat around its trunk and used fertilizer in March and June. But, the leaves are yellow.

I wouldn't see any reason to take it out and replace compost and peat every Spring. Compost and peat are both very acidic too, it would burn up the roots of a lot of plants. It might be a good idea to add sand or shredded bark to your planting mix to make it drain better, rhododendrons are somewhat sensitive to phytophtora (caused by poor drainage, root rot). Adding a few inches of a mulch that breaks down quickly every year will help replenish the soil.

Ok. Thank you.