GARDEN GURU

Q Last year I grew some white musk mallow from seed that has bloomed well this summer. What should I do now flowers are fading?

Chris Booth

A This a lovely, short-lived perennial with dazzling white blooms. You have two options: cut back the plants to encourage a later flush of flowers, or leave the stems intact to allow them to self-seed.

Q Can you tell me if it’s possible to split a mature forsythia tree without killing it? Kate Alderson

A You can’t propagate a forsythia by division. If you want to pass a bit on, the best way is to take semi-ripe cuttings before early autumn, or wait until its leaves fall and then take some hardwood cuttings.

Q Why are the lower leaves on my roses turning yellow and dropping off? I feed it with bonemeal in spring and spray the foliage against black spot.

Jennifer Biel

A Thanks for the photograph. Despite your best efforts to avoid the disease, it looks as if your rose has succumbed to black spot. Going forwards, I would suggest spraying the plant with Uncle Tom’s Rose Tonic. This is high in potassium and phosphorus, and will promote strong, healthy growth rather than lush shoots that are prone to disease.

The foliar feed can be sprayed every seven to 14 days during the growing season.

Also, pick up leaves as they fall to prevent spores overwintering.