Gardens: what to do this week

Clematis 'Big Brother': 'Its blooms are mammoth.'

Visit this

Whether you’re mad for mahonia or crazy about chrysanthemums, the national collection of your favourite plants is somewhere in the UK. Conservation charity Plant Heritage supports more than 600 national collections, helping to keep threatened plants in cultivation and promote biodiversity in our gardens.

Revive this

You planted a hydrangea, it flourished all spring, but now on hot days its leaves are wilting. Hydrangeas are the first plants in the garden to suffer when the soil dries out. Give them a long drink, then mulch heavily; if they still sulk once established, move to a moister spot come winter.

Plant this

Breeders just can’t leave clematis alone, resulting in ever-bigger blooms that won’t collapse at the first drop of rain. Join the clematis revolution by investing in new variety ‘Big Brother’. At 25cm across, its blooms are mammoth; even better, it flowers twice, in late spring and late summer. Height and spread 1.5m x 90cm. To order one jumbo plug for £14.99, or two jumbo plugs for £19.99, call 0330 333 6856 quoting ref GU359. Or shop online at theguardian.com/offers/plants. All orders include free p&p. Dispatched August to September.