Got a problem in your plot? Let our Garden Guru u Martyn Cox help you out

QI have two tubs of zantedeschia that produce a mass of healthy leaves but haven’t flowered for two years. Why is this? Valerie Fitchet

AThat’s hard to tell without knowing how you maintain them. I can say, however, that as yours are in pots, they may be congested, so divide in spring if necessary.

QOur magnolia is infected with a kind of fungal growth. Will it kill my plant? Keith Perry

ADon’t worry. The picture you sent me shows lichen, an ancient organism that grows on trees. It is unlikely to have a detrimental effect, and in fact it’s probably a sign that the air is clean in your area. If you have a question, email info@martyncox.biz