Question: I expected the usual glut of courgettes from my four plants this summer but they hardly got going before they stopped producing. I also had a pattypan plant that didn't produce one usable fruit. I thought I watered adequately so what went wrong?
Answer: The usual cause of a sudden halt to cropping is to allow fruits to get too big, which suppresses later ones. Outsize fruits are best picked and used as marrows, or consigned to the compost bin. Gather any remainder fruits, water the ground well, and with luck and a mild autumn more courgettes will appear, which should be picked and used while still young and crisp.
Patty pan squash are very reliable so it is unclear why yours did not fruit, but check that they have plenty of light and, as with all squash, note that very fertile soil gives the best results.
Question: A Russian vine I thought I had eradicated is showing again on a newly-planted plot. What will kill it please?
Answer: Cut it off at ground level, and treat the freshly cut stems with a weedkiller containing glyphosate, that is recommended for stump treatment - see the label. Suitable brands include Roundup Tree Stump & Rootkiller, and Deep Root Ultra Tree Stump & Weedkiller.
If you garden organically, however, you will have to dig out the roots and be ready to clear up any survivors next summer!
Send your questions for Guy Barter to: firstname.lastname@example.org.
Only a few questions per month can be answered. For further advice on handling problems in your garden, visit www.rhs.org.uk/advice/index.asp.