December NZ Gardening Guide Tips

NZ gardening guide December Tips

Summer is here for this NZ gardening guide! At least according to meteorologists, who record summer as being December, January and February. Although according to astronomers summer starts at the solstice ( the longest daylight period ), which is December 21st and ends on the autumnal equinox when day and night are each about 12 hours long on March 21st. The gardens are full of bloom and fruit at various stages of development. It’s now when you can tell how good your pollination has been with most pip and stone fruit showing small fruit developing. On commercial orchards fruit thinning will be considered. This is where some small fruit are removed if there has been a heavy fruit set. This will tend to increase the size of each fruit at harvest. You need to plan to have everything right for Christmas if you’re intending to have guests visiting, so you can reduce that last minute rush. It’s a good time to mulch around plants, but leave ventilation air space around the base of the plant. Piling mulch against the stem of plants can cause collar rot that can be fatal for the plant.

NZ Gardening Guide

Tasks For This Month NZ gardening guide


Watering – Some areas may be drying out, with cracks appearing in some soil types. To determine if your plants require watering you can buy a small water testing device at any good hardware store, or can dig a small test hole that allows you to see how moist the soil is below the surface. I generally prefer to water in the evenings to allow the water to soak in over night. Watering in the morning often means the water will be evaporated before it’s has a chance to soak in. Slug and snail – When you plant small seedlings you may want to sprinkle a few snail baits around each one or they may disappear over night. Remembering that some baits are poisonous to animals and birds, so need to be positioned safely, such as under a cover. Alternatively traps can be used. There are snail and slug baits that are not poisonous to birds and animals but they are more expensive. You can use the beer in a buried container trap method with some success. Ants Are often a problem especially in northern districts, so it’s best to get them before numbers build up by placing baits under the house and/or in places sheltered from the rain.

Planting –

Perennials You should have done all your perennial planting such as trees and shrubs by now to make the most of the growing season. But if you prepared to water during dry periods you can still get away with planting now.

Food Gardening

Vegetables –

Regular hoeing will kill most newly germinating seeds before they get established. Keep planting successive crops to ensure continuity of supply. When sowing seed be careful to allow enough space between each seed, so you don’t have to do a lot of transplanting. Most seedlings grow bigger faster in there’s no transplanting shock inflicted on them. Remove plants that are bolting to seed unless you want to get your own seed. Bearing in mind some plants don’t come true from seed, which means they may vary in characteristics from the original parent plants. Apply slow release fertilisers around your growing plants, but not in direct contact with the stem as this can cause rotting problems. I prefer organic fertilisers such as animal manures that increase the soil micro organism activity and earth worm populations. If you see tree roots in your vege garden it’s generally best to chop them off before they compete with your vegetables.

Veges to plant or sow

Beans (both climbing and dwarf), beetroot, broccoli, cabbage, cape gooseberry, capsicum, carrots, celery, chicory, Chinese cabbage, choko, cress, cucumber, eggplant, endive, Kohl rabi, kumara, leeks, lettuce, marrows, okra, peas, marrows, melon, mustard, spring onions, parsnip, pepper, potato tubers, pumpkin, radish, rhubarb (both seed or crowns), salsify, silver beet, squash, spinach, sweet corn, tomato, swede, turnip. Beans, cucumbers, pumpkins, and melons require minimum germination temperatures of 15C, the optimum germination temperature is 24C.

Herbs –

Plant and/or sow chervil, chives, dill, mint, parsley, rocket, sweet basil, tarragon, etc. Coriander requires continuous sowing, because it goes to seed quickly.

Fruit Trees

Pip and Stone Fruit –

Most of the flowering is ending, and you can see how many fruit have set for this seasons crop. If you want to control diseases and pests with chemicals, you will need a regular spray program though out the season. Once you start it’s best to keep going regularly, especially with insects. Citrus – You need to harvest all the fruit left on your citrus trees, because the tree will suck the moisture out of them and they will reduce this seasons crop. Feijoa – Are flowering now and the black birds are ripping into the flowers as if they’re trying to destroy them, but they still produce fruit afterwards. Berry fruits – Look for ripe fruit to pick before they become over ripe. Give them a continuous supply of nutrients by regularly applying fertilisers. If you’re into chemicals, you need to spray regularly. Raspberries, blackberries, boysenberries, and loganberries – Will usually need support for new growth, such as a trellis or galvanised wire mesh. I generally don’t like using plastic mesh because it breaks down in the sun and becomes brittle and breaks when the plants are heavy with fruit. Goose berries and Blackcurrants – Ensure they have a continuous supply of nutrients and water. Strawberries – Will need protect the berries from snails, slugs and birds. The birds protection usually consists of netting held in place by a frame. Ensure there’s a continuous supply of water and fertiliser.

Green Houses/Glass houses –

Daily watering will be needed for vegetables. Good ventilation is also important, to avoid overheating and too much humidity. Shading may need to be considered for sunny positions. Tie up climbing plants, such as tomatoes and cucumbers. Continue controlling any snails and slugs. Remove any bolting plants and decaying matter, weed and ensure a continuous supply of water and nutrients. Keep a succession of planting going as space becomes available.

Pot and Container Grown Plants

Move indoor plants away from direct sunlight that can get intensified through the glass and cause leaf burning where you end up with brown dead patches on the leaves. Watering may be required daily and including some diluted liquid fertiliser is beneficial to most plants. Repot plants that have finished flowering such as orchids. Remove dead leaves and dust with a damp cloth or spray. Control any insect or diseases.

Ornamental Garden jobs for Gardeners in NZ


Remove any dead flower heads unless it’s a once only flowering rose and you want the hips for decoration or jam. If you use chemical pest and disease control you need to continue regular spraying during the growing season. Check the soil remains moist, and water as needed.


Apply snail and slug control measures and remove weeds, preferably while they’re small. Sow seeds of: ageratum, alyssum, amaranthus, aster, balsam, bedding begonia, Californian poppy, carnation, celosia, chrysanthemum, cockscomb, coleus, Cleome, cosmos, dahlia (seed), delphinium, dianthus, everlasting daisy, galardia, gazania, geranium, gerbera, gloxinia, gypsophila, honesty, impatiens, kochia, marigold, mignonette, nastutium, nemesia, ornamental chilli, petunia, phlox, portulaca, rudbeckia, salvia, snapdragon, spider flower, statice, straw flower, sunflower, Swan River daisy, verbena, viscaria, and zinnia. Plant seedlings of: alyssum, aquilegia, canterbury bells, carnations, cornflower, cosmos, cineraria, delphinium, pansies, polyanthus, poppy, gypsophila, hollyhock, stock, and viola .

Trees and Shrubs jobs for NZ gardening guide

All your tree and shrub planting should have already been done by now to make the most of the growing season ahead. But you can still plant if you’re prepared to water during dry periods. Your hedges may need trimming after the spring growth.

Lawn jobs for NZ gardening guide

Mow regularly at least fortnightly, and don’t cut too low. The grass should be between 20 to 25 mm after you’ve cut it. If you’ve got a lot of weeds in your lawn such as dock that will be sending up flower spikes hoping to spread by seed, it’s a good time now to control them, either with spot herbicide spraying or digging out.

Compost jobs for NZ gardening guide

Continue adding to heaps and when they consist of predominantly unrecognisable matter they are ready to be spread around planted areas as a mulch, or dug into the soil. Make new compost heaps by incorporating dead leaves, grass clippings, vegetable scraps with a sprinkling of lime and animal manure etc. Turn and mix existing compost heaps that haven’t decomposed sufficiently. Happy Gardening for this months NZ gardening guide.

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