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Thank you all for your contributions.
The roses are open to sun in arc 150*-330*, so they get optimum exposure.
As a rank but fervant amateur, I have tended to water my roses (50 odd specimens) almost every other day, come hell or, even, high water! I have treated them lavishly with Toprose, and used Roseclear, Murphy's "Tumbleblite" and Bayer Multirose Concentrate to keep them free from almost everything....except a very few yellowing leaves, which you will advise me is owing to overwatering?
ALL varieties have received the same treatment, and all are prospering mightily save the Icebergs.
I am training stems to fan out over trellis work. As you implied Robinia lots of water for young plants seems reasonable; but I do take your point terambulan, and will deliberately limit the Icebergs watering schedule to a trickle!
I have thought of pruning mid-season because there is so much growth - to encourage budding instead of just stem/leaf explosion, if you 'get' me? What do you think...madness?! Many thanks again.