- Lily-lovers should be on red alert at this time of the year for a destructive pest called the scarlet lily beetle. This bright red, blackheaded creature is about ½in long and, along with its red-brown grubs (which are often covered in a slimy dark material), it feeds voraciously on the leaves and stems of lilies. It can cause considerable damage, including defoliation and poor flowering. The best control measure is to examine the lily plants every day and pick off and destroy these pests. It is also important to remove any plant debris and weeds from the surrounding area.

- If you have asparagus growing on the plot, stop harvesting the succulent young spears by the middle of this month at the latest - otherwise, the plants will be weakened and the crop is likely to be poor next spring. The remaining spears should be allowed to grow into tall, leafy stems, which will build up food reserves in the fleshy roots and replenish these perennial plants for the following season’s crop. Once you have finished harvesting, give the plants a boost by scattering an organic fertiliser over the soil surface.

- Dwarf rhododendrons are magnificent plants. My favourite types are the yakushimanum hybrids, which flower in late spring and early summer and form compact, dome-shaped evergreen bushes. For the best results, raise them in a sheltered, sunny (or partially shaded) spot and welldrained acid soil (a pH less than 7). Even if the garden soil is not suitable, you can plant them in half-barrel containers filled with ericaceous compost. Once the flowering display is over, snap off the spent flowers using the finger and thumb, as this improves the appearance of the bushes, helps to prevent diseases and directs the plant’s energy into producing new flower buds. When deadheading a rhododendron, always take care not to damage any buds or leaves growing underneath the old flowers. Rhododendrons are also shallow-rooting, so give them a good water and top up any bark-chipping mulches to retain moisture in the ground during dry summer weather.

- Chervil is becoming popular as a salad herb, and the leaves are an ingredient of fines herbes. In a partially shaded spot with a moist but welldrained soil, sow the seeds in ½in-deep drills. As soon as the young seedlings are large enough to handle, thin them to 6in apart. During the growing season, do not let the ground dry out, otherwise the plants may bolt (run to seed at the expense of the edible leaves). You should also keep the area weed-free. If flowering stems do appear, they should be pinched out to promote vibrant leaf growth. The bright-green, parsley-like leaves can be gathered, a few at a time, 6-8 weeks after sowing.

- Citrus plants that have spent the autumn, winter and spring in the protection of a conservatory will benefit from a long summer holiday outdoors. Harden them off for a week (position the plants outside in the day and move back under cover at night), then leave the containers in a warm, sheltered and sunny spot on the terrace. Keep the compost reasonably moist and add the occasional liquid feed. In early to mid-autumn, the citrus plants should be moved back to their main indoor lodgings before the frosts arrive.

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