The warm weather means the garden is ahead of itself and gardeners even busier. Many favour the "Chelsea Chop" traditionally done at the end of May, (see link to May Calendar) and so named as it coincides with the famous Chelsea Flower show. 

"The Chop" is cutting back bushy herbaceous and perennial plants to make a sturdier plant which will flower later. You can cut some of the same plants back, and not others, to encourage staggered flowering, and even chop parts of the plant. There is every reason to do it earlier this year as plants are further through their growing cycle on account of the warm weather.

If you are growing on bedding plants under cover, a similar principle applies. I would recommend you pinch out the top growth and prevent them flowering. Firstly, save the plant's energy to start flowering in the greenhouse is nice but you want the long flowering season in the garden. By pinching out the top growth and the embryo flowers you will encourage the plant to be bushier and it will flower slightly later when in situ in the garden,

This is an ideal time to do this and whether chopping or pinching look for bushy perennials with multiple flower heads, Nepeta (cat mint) Sedums, Hardy geraniums, Asters are ideal but not suitable for this treatment are flowers with single flower heads such as Delphiniums, Peony, Clematis. Look for bushy plants and most bedding plants will benefit especially those with a tendency to go leggy as the seasons goes on such as verbena and petunia.