Eric Robson visits Nicholas Parsons in his Buckinghamshire garden while Anne Swithinbank visits the Jodrell Laboratory at Kew Gardens to investigate the use of biological controls in the greenhouse.

Questions in the programme:
Q. I am quite successful growing courgettes from seed. However, some of my smaller fruit are turning yellow at the tip. Why is this?
Wet weather will cause the courgette flowers to rot. Next time you experience a really wet summer, try twisting off the flowers before they start to rot.

Q. I'm looking to reduce an area of scrub, mainly bramble, nettle etc and replace it with shrubs to attract bees. Which shrubs would the panel recommend?
First, be sure to clear the bramble roots well.

Planting suggestions: Dog roses, Ivy (for off-season flowering) and hawthorne.

Q. What is the secret of getting Crocosmia and Agapanthus to flower?
Agapanthus would need over-wintering indoors, ideally. Failing that, pot them up in the winter and insulate with fleece and bubblewrap. In spring, make sure they are exposed to adequate levels of sunlight.

Q. Is there a selective weedkiller which would kill the moss and weeds in my lawn but spare my violets?
Most lawn weedkillers target all broad-leaved plants, including violets. You would be better off manually digging up the weeds.

Q. How should Nicolas Parsons prune his Clematis 'Nelly Moser'?
In early spring, cut back to top-most large buds. This will give you the earliest bloom.

Q. What can I plant in my 6-inch bed - clay soil, shady and windy - located between my house wall and five-foot fence?
Try bedding plants in troughs.
Tolmiea menziesii or 'Piggyback plant'
New Guinea Impatiens
Heuchera

Produced by Amy Racs & Howard Shannon.
A Somethin' Else Production for BBC Radio 4. Show less