So far this has been an unusually dry and very pleasant spring. The winter wasn’t half bad either with less than normal rainfall throughout most of the Auckland area. This has resulted in slightly warmer soil temperatures and very easily worked ground that is great for gardening.
But when planting beneath the canopy of large trees, in exposed sites, or on the drier side of the house, the soil is already as dry as it was last autumn! In fact in more sheltered spots the winter rains have still not sufficiently wet the ground down below about 30cm to 40cm.
Since the season is rapidly progressing Into the traditional drier months the wise gardener should start to mulch most garden beds now in order to beat the dry weather that could turn an otherwise lovely spring into an early summer drought.
Especially vulnerable to dry weather are all shallow-rooting plants. While some of these plants have anchoring roots that can move deep into the soil they feed off of a network of fine root hairs just below the soil surface.
If these dry out the plant often doesn’t immediately die although it may wilt and recover at nightfall. But if this drying out persists the plant cannot feed properly. This can stop the formation of flower and growth buds for the following season or weaken the plant so much that it becomes the victim of disease.
Among the most important plants to mulch now are azaleas, rhododendrons, camellias, daphne, ferns, fuchsias, all shade or forest-loving natives, many moisture - loving perennials like astilbe and spiking lobelias, and softer annuals like pansy and tender zinnias.
Many materials make excellent mulches. These include nitrogen-enriched barks, compost, leaves and straw, aged manures, gravels and scoria, stones, the finely chopped prunings and clippings from hedges and trees, weed mats and black plastic, cardboard, newspaper, untreated wooden planks, and dry grass clippings.
Avoid heaping fresh manures or wet grass clippings around plants and shrubs. These are liable to heat up through decomposition and can burn the plants. Sometimes they will even release toxins into the soil and poison the plant.
When mulching check to be sure that the soil is deeply moist. If it isn’t, artificially water as deeply as possible before spreading the mulch otherwise it will seal in the dry rather than hold in the wet. Spread the mulch in a generous layer right out to the dripline (outer edges of the foliage) and in to the trunk.
Keep the mulch off the trunk itself to help prevent rots and insect problems like borer. If using an organic mulch it should be at least 5-10 cm. deep to be very effective. A mulch of 20cm is not excessive for larger trees and shrubs in drier or exposed situations.
While saving on the summer water bill, a well-laid mulch virtually eliminates weeding. Eventually it will break down into a fine compost, feeding the soil just like a fertiliser enrich it’s quality, saving you time, money, and the garden!