Questions, answers and jobs for the coming week

Mimosa
Mimosa
Chrysanthemums bought in pots and added to the border look great in autumn.

BRIAN KIDD: Mum’s the word for an added splash of autumn fire in borders

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Brian answers readers’ horticultural questions

Why does my potted mimosa (pictured) grow well in spring but after a short time the leaves fall off? MH, Lee-on-the-Solent.

It needs new compost. Knock out of the pot and shake off all the old compost. Wash pot, put pieces of crock in the base and use John Innes number 3 compost to be successful. This will keep the plant well and will produce flowers during the spring of 2016.

What is wrong with our blue flowering shrub? It dies in patches. We have cut out the affected material but the problem continues. DQ, Copnor.

This is die-back and is common on old shrubs, especially in dry seasons. Give the shrub a slow feed of Maxicrop Complete fertiliser. Five gallons is about right. In spring, or after the shrub has finished blooming, cut back hard and drench again with Maxicrop. You must apply this very slowly because the roots are dried out.

A weed is invading my daughter’s lawn. She has used two different weedkillers but things have not improved. Can you help? S, Cosham.

This persistent weed called self-heal spreads by seeds and underground shoots. It’s not easy to eradicate. Lie two lines of bamboo canes three feet apart across the lawn. Dilute Verdone Extra lawn herbicide and with a pump sprayer, treat the areas between the canes. The spray must cover the grass and weeds. Cover entire lawn. After a week the weeds will start growing faster than the grass. Repeat the spray and do it again next spring.

JOBS FOR THE WEEK

Most gardening books recommend pruning Autumn Bliss raspberries in February, but here in the south canes can be cut down to soil level as soon as they have finished fruiting. After pruning, a top dressing of well-rotted manure is applied all over the bed. A four-inch layer is perfect.

Are you making leaf mould? Put 12-inch layers of leaves in old compost bags turned inside out. After each layer sprinkle on one part urine to seven parts water. It will be ready in 12 months.

Take off every rose leaf which has black spot and bin them. Pick up all fallen leaves too and spray roses with Bordeaux powder dissolved in water. Spray the bushes and the soil.

Plant a few narcissus bulbs in a flower pot in John Innes number 2 or 3 compost. Put in the cold greenhouse for an early display in your lounge in February.

Pick off yellowing leaves on all types of cabbage, especially Brussels sprouts. This encourages air flow below the crown and reduces the disease which causes sprouts to rot.

Plant crocus corms any time between now and December, choose separate colours, Don’t buy mixed because from a distance, the white flowers look as if someone has dropped litter in the drift of flowers.

You have probably lifted your potatoes, allowed them to dry in the wind before half filling the potato sacks. Check them this week to ensure there are no rotten tubers in the bags, If you smell a strange smell in the shed – it’s rotting potatoes.