By Microlite
Essex,
United Kingdom 
I have two red robinas in my front garden, which is around 5m * 5m and slopes top to bottom by around 1m. One plant is at the top and one is at the bottom. Both get the same amount of sunshine, water etc. The one at the top of the garden is growing really well, both red and green leaves plus flowers, the one at the bottom seems to be continually strugging, the red leaves fall off and is not as densely packed with leaves, what could the problem be?
21 May, 2010
Answers
BTW I think you are talking about Photinia x f. 'Red Robin'. Robinia is a tree with yellowish leaves.
21 May, 2010
Thanks for responding and yes I think I have got the name wrong sorry - Red Robin. new to gardening or should I call it killing off plants.
21 May, 2010
Do you think it might be salt that's the problem?
If not, then I bet someone on here will be able to come up with another suggestion.
21 May, 2010
When a plant at the bottom is doing porly, and one at the top is fine, I always suspect drainage problems, or--around here--too much watering.
21 May, 2010
If there is a footpath at the bottom of the slope, then I'm wondering if it might be salt that's the problem. Salt from gritting paths and roads is not good news for plants, even if you can no longer see the salt, it's still there in the soil
21 May, 2010