Weekend Work: Time to treat clumps of Solomon's seal

What to do

Clumps of Solomon's seal are prime targets for sawfly caterpillars. If you are squeamish, treat them with pesticide – otherwise, pick them off and stamp on them.

Roses should be deadheaded regularly. Take off the flower and the leaf below it, cutting the stem just above the following leaf. Tidy up bushes of philadelphus and weigela as soon as they have finished flowering, cutting back at least a third of the old flowered stems to make way for new growth.

Cut back the old flowered stems of sweet rocket close to the base, unless you want to encourage it to self-seed.

Pick over clumps of pinks regularly, nipping off dead heads to encourage new flowers. If you want to increase your stock of carnations and pinks, layer them by pegging down shoots on the outside of the clumps. They should root within weeks.

Cut back herbs such as sorrel and tarragon which are beginning to look scraggy. Tarragon will sprout again quickly.

Last year's parsley usually shoots up to seed around now. This is your cue to sow a new row of seed. If the ground is very dry, moisten it well before sowing. Keep basil plants well watered and fed so that they produce plenty of fresh leafy growth.

Stop cutting asparagus to allow it time to build reserves for next year. Keep beds well weeded.

Watch out for attacks of mildew on gooseberry bushes. Spray plants with a systemic fungicide.

For whitefly in the greenhouse: knock the plants first to set the whitefly on the wing and then just hoover them out of the air.

What to see

The Hampton Court Palace Flower Show opens on Tuesday and runs until Sunday 11 July. If you are not a member of the Royal Horticultural Society you can't get in until Thursday when an all-day ticket (10am-7.30pm) costs £30 on the gate. If you go in after 3pm, you pay £19. New this year is the Gardens Illustrated pavilion featuring some of the stylish plants and products that appear monthly in the magazine. For more information about the show, go to rhs.org.uk/hamptoncourtpalace