By Joanne Cho, PCC Seed Bank Coordinator
Welcome to the winter garden!
What comes to your mind when you think of winter gardening?
Perhaps lush brassicas such as cabbage, kale, broccoli, and even Brussels sprouts growing vigorously and abundantly? Well, if you have an organic vegetable patch full of thriving winter crops right now, you are one of the lucky ones—and you deserve my envy! I certainly have much to learn from you. My reality is rather different. As soon as I sow or plant brassicas, white cabbage moths and a host of other creatures seem determined to destroy them faster than I can protect them. If you are one of those fortunate gardeners with a successful winter crop, please consider donating some seeds to our Seed Bank. At present, our supply of winter vegetable seeds is almost non-existent.
Let’s take a closer look at winter gardening and explore how we can make the most of this season.
Why is Winter the best time to build soil?
Winter is often the ideal season for building soil because nature does much of the work for us.
1. Mulch Breaks Down Slowly and Effectively
Cool temperatures and regular rainfall keep mulch moist throughout winter. Fungi, worms, and microbes gradually convert leaves, wood chips, and straw into valuable humus.
2. Less Competition from Plants
Many plants grow more slowly during winter, so nutrients released from compost and mulch are stored in the soil rather than being immediately taken up by fast-growing plants.
3. Earthworms Become Active
In areas with reliable winter moisture, earthworms pull organic matter into the soil and improve its structure, drainage, and fertility.
4. Winter Rains Carry Nutrients Downward
Mulch and compost applied during winter are gently washed into the soil profile, feeding plant roots and supporting beneficial soil organisms.
5. Time for Cover Crops and Green Manure
Green manure is a crop grown primarily to improve the soil rather than for harvest. Instead of eating it, you chop it down and leave it on the surface as mulch or lightly dig it into the soil.
Winter is an excellent time to grow green manure crops such as:
- Broad beans
- Field peas
- Vetch
- Clover
- Lupins
These crops protect the soil, add organic matter, and many of them fix nitrogen from the atmosphere. However, do you find that some of these crops are prone to fungal diseases? I certainly do in
our humid Central Coast climate. So, what are some good alternatives?
For non-leguminous green manure crops, consider:
- Oats
- Radish
- Mustard
- Barley
- Cereal rye
- Chicory
- Plantain
For nitrogen-fixing legumes that cope better with moist conditions, consider:
- Cowpeas – In our area, it grows better from October, not in the cold winter.
- Balansa clover – grows well in our winter. Tolerates waterlogging better than most clovers and produces large amounts of biomass.
- Persian clover – fast-growing even in winter and performs well in moist conditions.
6. Tree Planting Season
For food forests, winter is the perfect time to:
- Plant fruit trees.
- Add compost around future planting sites.
- Sheet mulch new areas.
- Establish guild plants before spring growth begins.
7. Fungal Networks Thrive
Food forests depend heavily on fungal networks. Cool, damp winter conditions encourage fungal growth, helping transport water and nutrients between plants and improving overall ecosystem health.
8. Spring Rewards Winter Work
Gardeners who spend winter:
- Mulching
- Composting
- Planting green manure crops
- Protecting bare soil often find that their spring growth is dramatically stronger and healthier.
Sheet Mulching: Preparing for Spring Success
Another excellent winter task is sheet mulching. Sheet mulching is a method of creating new garden beds or improving existing soil by
covering the ground with layers of organic materials. It mimics the way a forest naturally
builds rich soil over time.
Basic Sheet Mulching Method:
- Mow or flatten existing grass and weeds.
- Water the area thoroughly.
- Lay down overlapping cardboard or several layers of newspaper.
- Wet the cardboard thoroughly.
- Add compost, manure, or other nutrient-rich materials.
- Cover with 10–20 cm of mulch such as wood chips, straw, leaves, or sugarcane mulch.
The cardboard suppresses weeds while gradually decomposing. Worms, fungi, and microbes then convert the entire layer into rich, fertile soil.
Winter may seem like a quiet season in the garden, but it is actually one of the most productive times of the year. By building soil now through mulching, green manure crops, and thoughtful preparation, you will be rewarded with stronger growth, healthier plants, and more abundant harvests in spring and summer.
Happy winter gardening, everyone!