In mild areas of New Zealand, tender plants can survive outside over winter with some shelter. But in cold or exposed areas, even hardy plants may need some protection from the cold and wind. Evergreen plants and pot plants are at particular risk of damage, so pay them special attention.
How to protect your garden plants in winter:
Physical protection can be used to insulate plants from cold or wind and should be put in place before the first sign of frosts. Plant wrapping can be made from materials such as fleece, hessian, straw and polystyrene. Take care to prevent sweating and possible rotting; protective covers should be removed when extended periods of very mild weather are forecast. But remember to put it back if the weather is predicted to become cold again.
Exposed soil in wet winter conditions can result in leaching and loss of nutrients. Sowing winter tolerant annual plants (often known as green manure), such as mustard and lupins, in March, reduces leaching and provides cover for the soil. The young plants will hold nutrients until they can be dug back into the soil in spring.
This can help maintain soil temperature, reduce compaction, and prevent soil erosion due to heavy rain.
Avoid applications of nitrogen-rich fertilisers late in autumn, as they stimulate new growth that would be more susceptible to winter damage.
Deal with drainage problems before winter. Wet soils will make young or shallow-rooted trees more vulnerable to uprooting in strong wind. Also, few plants like to have their roots in waterlogged soil for long periods.
Plants in Pots
Place outdoor pot plants in drier, sheltered locations. They can be grouped together for mutual protection. Do not allow roots to freeze in containers by insulating the containers with bubble wrap or straw.
In late autumn check all garden structures to ensure they are secure and will not get blown over in windy winter conditions. Fences that are 50% wind permeable avoid turbulence and shaking of the fence, so they are less liable to collapse.
Your garden is a microclimate of its own. It will have warm places, such as the bottom of north-facing walls, and cold or wet places such as the shaded south side of walls or buildings. Choose plants for these positions based on the plant’s tolerance of cold and shade. Situate early flowering plants such as Magnolias and Camellias so that they do not get the sun in the morning, because rapid thawing of frozen buds can cause blackening and buds to fall off.
Windbreaks will provide protection from wind and cold. The thoughtful placing of temporary windbreak netting or similar materials on well-secured strong posts will help in the short-term, but additional planting such as hedges can provide longer-term, natural windbreaks.
Pests and Disease
Do not ignore your dormant garden in autumn or winter. It may look like nothing is happening in the garden but lurking among the leaf litter, bark, and dead twigs, are the spores of diseases and the eggs of pests.
In frost-free weather, prune and destroy dead, damaged, and diseased parts of trees and shrubs. Then protect them from disease and pests using winter protectants, copper spray, McGregor’s Spraying Oil, and sulphur. This will control fungal spores and insect eggs on the trees and prevent fungal and bacterial disease entering through damaged parts of the plants. Spray again after any pruning and throughout winter.17 June 2021