Hi!

We bought our house about 10 years ago at which time the whole front embankment was full of tall rhododendrons (I believe Rhododendron Maximum). Over the years we have had more than I would like die and I was wondering what their normal lifespan is? I attached a panorama shot, the right side of which includes most of the removals. The left side is still doing well.

I had a specific question about root rot. One photo shows the base of one giant rhododendron (15 ft tall) from which you can see 3 large branches growing out from. Well there used to be 4 or 5. The others ended up with all their leaves dying so I removed them - and it was pretty easy, I just pushed it over and it broke off at the base. You can see the bottom of the most recent dead one in another photo

Ok so I guess I'm wondering whether they are dying from old age or disease and if it's disease how can I save all the others

Rhododendrons including Azaleas can at times be unpredictable. Briefly they are classed as surface rooting. Simply meaning that their roots are very close to the soil surface. Here in the UK. It is a somwhat trick question asked of student gardeners. 'When do you hoe around rhododendrons? Answer. You DON'T. Because of the surface roots.

Rhodos' can be a bit fussy . They often dislike direct sun. Their preference is a shady woodland site. They belong to the Ericaea family, hence the soil pH should be below neutral an much on the acid scale, close to 4.5-6.0

Viewing your panoramic photo. You have a good supporting area of trees affording protection. Another dislike of theirs is wind and frost. Perhaps finally, they will suffer, even to the point of death if the root ball becomes dried out.

Your photo shows them growin an raised area. Whetherornot this has allowed low winds to enter the soil and causing some drying out. I can't say. Neither can I consider some unseen disease etc. As with most shrubs. It can be a wise choice to periodically cut out the old heavier wood. This will encourage fresh ne growth, albeit rhodos can be very slow growing.

Watering can be nightmare at times. In many areas around the world. Domestic water supplies usually have been treated and such treatments can contain residue of chlorine and lime. Both are not enjoyed by most plants, irrespective of the pH requirements.

May I suggest you prepare for the future by taking cuttings, by grafting, layering and or by collecting seed and sowing this. Layering is the simplest method. Seeds can take a lifetime to produce flowering plants. I do hope this information is of help. Best wishes and happy gardening.