A perennial is a plant that lives for more than two years and can also mean a plant whose top growth dies down in winter and re-grows the following spring. Some perennials keep their leaves all through the year.

They enjoy an almost limitless variety of names and growth habits, colours and seasons of flowering and offer the gardener a satisfying return for the investment of their time.

If a large selection of these plants are grown, flowers will be in bloom throughout the year. Soak well once the soil has dried out.

With the hot summer months approaching, herbaceous perennials should be mulched with either manure or compost when planting.

During winter, keep perennials nearly dry to avoid the roots rotting and the loss of plants during their dormant period. Very little water is required once top growth begins to die, which is always during the colder months.

One important aspect should be mentioned when growing perennials e.g. thymes, phlox sublata etc., is that the spread of these plants should be taken into account as they compete with other plants which may result in losses.

Avoid adjoining groups of plants having more than one degree of variation in spread of growth. If a spreading perennial reaches up to 45cm, avoid planting it beside one that reaches 60cm.

As well as the perennials mentioned above, they are grouped botanically into carnation, chrysanthemums, hollyhock, agapanthus, delphinium, acanthus, kangaroo paw, foxglove, geranium, day lily, lobelia, gazania, hosta, red hot poker, iris, lupins, nepeta [cat mint] poppy [papaver], viola and salvia.

In spring, perennials can be divided.

The easiest to divide are those with succouring rhizomes e.g. shaster daisies, asters and phlox.

Trim the rhizomes to about half length if long, and plant in new soil.

When propagating evergreen perennials the rooted section of the self-layering variety can be cut off and re-planted. To layer, weigh down the stem, covering them with a little soil.

It is 200 years since the Botanic Gardens in Sydney first commenced and the calyx is the latest development recently opened. Visiting there earlier this month, I noticed a Norfolk Island hibiscus, a tree that grows to approximately 50 feet with a vertically shaped flower like a hibiscus.

Until next time, enjoy the season of spring gardening.