Gareth Carter: Preparing your autumn garden

We have had fantastic rainfall over the past couple of weeks that has replenished soil moisture levels, writes Gareth Carter.

Sometimes at this time of year our gardens will be under much heat stress and drought – not this year! We have had fantastic rainfall over the past couple of weeks that has replenished soil moisture levels. The level of rainfall has brought forward the opportunity to start seasonal autumn planting. If you are on lighter, sandy-type soils then now is a great time to start applying mulch. This will help to lock in the moisture and to keep the soil cooler; it will reduce weed growth too.

If you are planning on sowing a lawn this autumn then starting on preparation – removing of weeds, old grass and spraying now is recommended.

During February in our late summer period, many gardens reach their full beauty. Bedding plants are at their best and brightest and the orange and yellow marigolds and the various colours of petunia, lobelia and geranium brighten many a border, pot or container and hanging basket. Another flower at its best is the tropical impatiens with their bright-red, pink and white flowers making a stunning display and are a good addition for a shady spot.

One of the heat-loving perennials that has really caught my eye this summer is the gaura. Commonly known as the butterfly bush, these plants stand up to the full sun and flower prolifically through these hot summer days. They are really dry hardy and there are a number of varieties available, in colours ranging from pinks, rose to pure white. They generally form a small bush about 30-40cm high and wide. If you have a little gap where you would like some summer colour then I highly recommend these.

Another of strong recommendation is the recently released Salvia Amistad. The family of salvias are long known for their hardiness to drought, hot sun and constant flowering. The salvia family is a diverse range of varieties in many colours, flowering from summer late into the autumn months. Salvias are part of the mint family, also referred to as sage. Like the herbs, the leaves are delightfully aromatic when crushed. In Latin the name salvia means healthy, feel well or to heal, given the healing properties of some varieties.

Amistad is a recent release into the populous world of salvias. It has exquisite deep purple blooms which emerge from black coloured buds. They put on a stunning display perched on top of its tall stems of green foliage. It is reputed to flower from spring until the first frost and through the winter months in warmer areas. Salvia Amistad has coined the common name of the friendship plant as the word amistad is Spanish for friendship.

Amistad is easy to grow, in well-drained soil. Feeding annually in spring will encourage lush new growth and good flowering for the coming season. The plant should be trimmed after flowering or whenever it gets untidy. If necessary it can be cut back to 15cm high, from which fresh foliage and subsequent flowers will arise.

Amistad can be grown in pots on the patio for colour, right through the summer BBQ season, or it is great in the garden where it will reach 70cm high, providing height and depth of colour.

Summer lilies are another favourite blooming at the moment with many varieties releasing a fragrance that makes the air heavy with a sweet scent. English lavenders and a number of roses will produce another flush of flowers and grace many a garden with a blaze of colour. Agapanthus are looking stunning, as are the summer-flowering gum trees (Eucalyptus Ficifolia) that are flowering around Whanganui.

Often at this time of the year, gaps can appear in borders. Planting perennials such as the aforementioned gaura and salvia that flower later in the summer will help keep the borders bright over the next couple of months. Other late-summer and autumn flowerers to look out for include chrysanthemum, rudbekia, echinacea, dahlia and alstromeria.

The use of climbers such as clematis, honeysuckle and pandorea envelope fences and scramble up pergolas, trellises and over arches, to offer privacy and seclusion. Roses require attention at this time. Spent blooms should be removed at regular intervals during the flowering season, not only for the tidiness of your plants but to prevent the formation of seed heads, which wastes the plant's energy. When flowers or spent blooms are cut, a reasonable length of stem should be removed. New shoots have generally started to develop on the old flower stem and a clean cut should be made just above one of these. This will encourage healthy growth and more flowers.

If your soil has acidic tendencies or if heavy dressings of organic materials are applied annually, then a light application of lime will be of benefit around your roses. When feeding, make sure the fertiliser contains sulphate of potash – it helps to harden growth and makes the plant less susceptible to disease. Potash will aid flowering and may also help to intensify colour in the flowers. Feed roses using Yates Dynamic Lifter, Novatec, or Tui Rose Food.

Keep an eye out for the spread of pests and diseases on roses. Maintain regular sprays to control aphids, rust and blackspot. A good spray is Combat 3 in 1 for Roses - a combination spray of insecticide, fungicide and a natural fish fertiliser with minerals and trace elements. Remember, ensuring your roses are well watered and fed is your first defence against pest and disease.

February is the first of the bulb planting months. In stores there are now ranunculus and anemones in mixed and individual colours as well as crocus, hyacinths and daffodil bulbs. They are excellent for borders, garden edges, pots and tubs as well as great to grow as a cut flower. More about bulbs in the coming weeks!

Have a good week.

Gareth Carter is general manager of Springvale Garden Centre