Monty Don's garden at Longmeadow is now under full sail but needs a gentle steer to keep it looking beautiful all summer long. This week Gardeners' World is all about tweaking and tidying, whether it's thinning or pruning trees, improving the soil or collecting seeds from spring and early summer-flowering plants, there are plenty of small jobs still to be done in the garden. Carol Klein is in Kent meeting lavender expert and breeder, Dr Simon Charlesworth, whose stunning walled garden is packed with many varieties of this beautifully scented plant. And Joe Swift visits the founder of the Mulberry fashion label, whose Somerset garden is a design classic