By Dutchy
United Kingdom 
I have planted Photinia Fraseri Red Robins close to drains, will keeping the the trees compact and about 5 feet high keep the roots shallow and compact and prevent them entering the drains.
30 Jul, 2014
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There's no way of knowing - Willows would almost definitely enter the drains, but with other shrubs, it depends on how dry they get and where the roots venture to. If there's sufficient moisture when they need it, they're less likely to penetrate drains in search of water. I've never found one yet that's penetrated the drains, even though one of my clients has a photinia hedge next to one.
30 Jul, 2014