Adequate moisture key for azaleas, rhododendrons

Many spring-flowering shrubs are pruned as soon as they have finished blooming. This is so the plants can make new growth over summer and autumn, as it is on this new wood that they flower next season.

Clematis, which has its peak flowering next month, is often left to grow unchecked, but most types can be pruned hard after flowering. Cut C. montana to 1m above ground, leaving only a main stem with two to four buds to develop.

Rhododendrons and azaleas can still be planted. They are shallow-rooted, with fibrous roots close to the surface, making them easy to transplant. Set the shrubs with the highest roots just 2cm to 3cm below the soil surface. Adequate moisture is vital to this group, so mulch around the roots with rotted autumn leaves, pine needles or old sawdust from wood that is not tanalised. Being woodland plants, rhododendrons and azaleas need an acid soil, so never apply lime. Azaleas come in two types — evergreen and deciduous — and the latter have colourful autumn foliage in orange or red. Winter roses (Helleborus) can be divided this month. They do better in semishade rather than full shade, and can be boosted with leaf mould or well-rotted cow manure.

Plant pansies and violas. Regularly remove faded flowers and seed pods to prolong the flowering displays, a practice also invaluable with other annuals and perennials, such as dahlias, sweet peas, asters, roses and calendulas.

Any dahlias left in the soil during winter can now be lifted and divided for replanting during the next four weeks. Lift clumps of tubers with a fork and, with a sharp knife, remove individual tubers, ensuring each has a large piece of stem with a sturdy growth bud attached. Before replanting, add plenty of compost or well-rotted stable manure. Add lime, at the rate of 100g a square metre, and replant the tubers with the growth bud about 5cm below the surface.

Plants suitable for damp spots in the garden include Astilbe, globe flower (Trollius), Himalayan blue poppy (Meconopsis), perennial phlox, primulas, japonica, leopards bane (Doronicum), Anemone japonica, lily of the valley, Solomons seal, hellebores and penstemons.

Roses should have been pruned by now. If not, this should be done as soon as possible or flowering will be late and blooms disappointing.

When bulbs grown in pots for indoor or patio displays have finished their flowering, plant them in a corner of the garden to recuperate. It will probably take a year or two before they will flower properly again. — The Star Garden Book