December Gardening Tasks

The first month of summer brings a burst of almost unbelievable growth. Fresh vegetables planted in early spring are ready to harvest, flowers are blooming, and the whole garden feels alive. It’s also a great time to tidy paths, trim overgrown plants, and refresh pots to create inviting outdoor spaces for Christmas entertaining and summer BBQs.

Vegetable & Herb Garden

Harvest

Courgettes are at their peak; pick them small and often to keep plants productive and avoid oversized fruit.
Powdery mildew can appear during warm, humid weather; good airflow and consistent soil-level watering help reduce its impact – read more advice here.
Herbs such as basil, mint, chives, parsley, and rosemary thrive with regular picking and are perfect for summer meals.
Regularly harvest leafy crops to encourage fresh, tender regrowth.
Early planted potatoes may be ready to be harvested in time for Christmas.

Plant

Keep sowing and planting quick crops like basil, rocket, lettuce, beans, cucumbers, radish, spinach, and spring onions to maintain a steady supply.
Succession planting lettuces and leafy greens every few weeks helps avoid bolting in the heat and keeps salads coming.
For later-summer harvests, plant beetroot, carrots, celery, corn, onions, silver beet, and more courgettes/zucchini.

Maintenance

Provide temporary shade for new or young seedlings during the hottest part of the day to protect them from heat and prevent wilting.
Water plants deeply to support strong, steady growth through extended dry spells.
Tomatoes carry heavier fruit now - support trusses, regularly check for pests and diseases, maintain good airflow, and water consistently to reduce blossom-end rot.

Grapes

Vines put out vigorous growth this month; remove excess shoots and train fruiting stems along wires to maintain airflow.
Water deeply during dry spells, especially for young vines still establishing their framework.
Thin grape clusters lightly if they form too densely - this improves air movement and helps fruit ripen better later on.
Remove basal shoots (suckers) to keep energy focused on productive growth.
Provide temporary shade for young vines if they wilt during intense heat.

Fruit Trees

Early variety peaches, plums, apricots, and cherries begin ripening towards the end of the month. Harvest fruit when it smells fragrant and comes away easily.
Lightly prune where growth is not required to improve access to fruit and airflow where branches are overcrowded.
If you planted new fruit trees over winter, keep a close eye on them and check regularly for water and nutrient needs.
Net trees if birds become troublesome.
If you haven’t set a codling moth trap for your apple trees yet, get on to it asap. Trapping early helps break the cycle and protects developing fruit – read more here.
Applying mulch around trees now helps conserve moisture and suppress weeds around the root zone.

Berry Fruit

Strawberries, blueberries, raspberries, boysenberries, and hybrid berries ripen rapidly – pick daily, ideally in the morning to encourage continual fruiting and stay ahead of birds.
Water strawberries sparingly and only when soil becomes very dry to avoid disease.
Top up mulch around berry beds to help keep roots cool during hot spells.
December is peak season for many raspberries - thin excessive new growth and tie up fruiting canes for easier picking and better airflow.

Flower Gardens

Summer bloomers are vibrant now; regular deadheading keeps flowers coming and helps prevent disease.
Thin overcrowded plantings to improve airflow, especially in humid conditions.
Fill any gaps with heat-loving annuals like asters, ageratum, cosmos, marigolds, petunias, strawflowers, salvias, and zinnias.
Containers and hanging baskets can dry out super fast quickly so water in the morning and consider adding Daltons Garden Time Water Storage Crystals.
Hydrangeas look stunning now. Keep them well watered to help them cope with afternoon heat and hold their blooms through summer.

Roses

The first burst of summer flowering on many rose bushes is now finishing.
Time to give plants a light summer pruning to stimulate new growth and a fresh wave of blooms early next year.
Mulch with either with Garden Time Compost or Premium Mulch & Feed to help keep the root zone cool and moist.
Water deeply and regularly, particularly during dry spells, aiming at the soil rather than the foliage.
Diseases such as black spot and rust often appear at this time of year - remove affected leaves from the property (do not put in compost bin) and consult our How to Grow Roses guide for advice on treating.

Indoor Plant Care

Many indoor plants thrive in summer warmth but can scorch if placed too close to sunny windows — keep foliage away from direct afternoon sun.
Ensure plants receive bright, indirect light and maintain consistent watering without overwatering.
Mist humidity-loving plants or group them together to create a more humid microclimate.

Mulching & Watering

Top up mulch across garden beds to help retain moisture and protect soil.
Check irrigation systems and hoses before heading away for the holidays. A timer can be a game changer during hot spells.
Watch for signs of plant stress: drooping leaves, dry soil, or scorched foliage appear quickly in late December. Give them a hand by applying Daltons Garden Time Seafeed or Kiwi Garden Plant Stress Solution.

Container Gardens

Containers heat up quickly and dry out faster than garden beds - water in the morning and monitor soil moisture closely.
Apply a layer of mulch, decorative bark, or stones on top of containers and pots to help lock in moisture and give them a tidy, finished look.
Move pots into gentle afternoon shade or under trees if plants are showing signs of heat stress.

Hedges

Trimming hedges early in December is a good way to make the most of summer growth.
The key to growing a dense, healthy hedge is regular, careful pruning to encourage plenty of new growth.
Like any plant, hedges respond well to fertilising - it helps support good growth, strong leaf colour, and flowering on varieties that produce blooms.

Lawn Care

Avoid mowing too low - slightly longer grass shades the soil, protects the roots, and helps retain moisture.
Irrigate in the cooler parts of the day, especially the evening, to soak into the roots overnight.
Keep mower blades sharp for a cleaner cut that reduces lawn stress.

Pest & Diseases

Warm weather brings out a whole mix of pests - aphids, thrips, whitefly, mites and caterpillars can all appear quickly at this time of year. A quick daily check of new growth makes a big difference, and catching problems early keeps everything far easier to manage.
Healthy, well-watered plants with good airflow are far more resilient. Giving them a regular feed and removing any damaged leaves as you spot them helps keep growth strong and reduces the chance of disease taking hold.
Read our Q&A’s for help identifying and treating common pests and diseases.