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Writing this on a below-freezing day seems appropriate. We’ve just avoided the first frost, lifted our tender perennials, and staked overwintering kale, sprouts, and broccoli. The beds are weeded, scrubbed down and, those that need it, are covered with fleece tunnels.
Yet, with twelve more weeks of true winter, and plenty of cold spring nights ahead, there’s tons more to do to prepare our no-dig raised beds for winter.
Preparing your raised beds for winter is crucial for early sowings in spring, and can reduce stress on overwintering plants. With tips on choosing the best mulch for winter raised beds, to basic maintenance hacks, there are all sorts of little jobs that prove that it’s just as important to garden in winter, as it is through spring and summer.
What is no dig gardening?
No dig gardening, despite this article’s title, does not necessarily mean building raised beds. The principle is simple; by enriching garden soil through mulch, and spot cultivation, we feed the good bacteria, encourage more biodiversity, and in turn, our garden produces healthier stronger fruit. And, in the context of this article, our soil stays warmer for longer and heats up faster in spring.
The big benefit of using no dig raised beds, is that by covering the ground with ½ inch of compost, mulch, or soil, you also remove the need for weeding, as most annual weeds, and some perennial weeds will fail to grow back from that depth.
Creating a no dig raised bed that can survive winter is really pretty simple. The binding principle is mulch, mulch, mulch. Any bed with healthy soil is teaming with life that will raise the temperature fractionally above the air temperature.
How to prepare no dig raised beds for winter
Whether you’re overwintering veg, or fighting against frost that’s already set in, winter is a fantastic time to get your garden ready for next year, and even continue harvesting. Obviously, depending on your climate, there are differences in what will grow, but even here in a chilly zone 7, we manage to grow winter cabbage, and salad crops and keep brassicas going.
Our successes don’t come without a little bit of hard work though, so we thought we’d put together an easy-to-follow, step-by-step guide to preparing your no dig raised beds for winter. The guide below is our standard annual plan, but if you’re in zones 9-11, there are some parts you can skip.
Note: If your gardening year ends in fall, with a late squash harvest, and there’s no veg left to tend to, skip steps 8-10.
1: Clear out old vegetables
From squashes to tomatoes, and salads to potatoes, any summer or fall vegetables that are still in the ground should be removed as soon as they finish cropping. If they’re still in the ground by early winter, harvest them before the first frost.
Falling foliage and rotting stems can harbor fungal spores and bacterial infections which will overwinter in the soil, even below freezing temperatures. And pests that have laid their eggs in the underside of foliage will remerge as larvae from the soil in spring.
If your plants look happy and healthy, compost them. If they’re turning brown, or black, or have any signs of rust, burn them (make use of the fire with an enclosed burner near your workspace!).
2: Remove all perennial weeds now
Any weeds, particularly perennial weeds, should be removed before they die back. When they grow back in spring, they can quickly set seed and will be harder to remove. Dig out the roots, and take care not to let any dry seed pods fall.
3: Warm your water
Warm up your watering cans in winter! Even in the depths of winter, the sun will warm water left in buckets or watering cans to well above the air temperature and even above the insulated soil.
When you’ve used one batch of water, refill the bucket and leave it in the greenhouse to warm up. The warmer water will help defrost soil around winter crops, and won’t shock greenhouse crops.
If you don’t have a greenhouse, leave buckets or watering cans up against the wall of the house. This will reduce the chance of them freezing, and they’ll warm faster in afternoon sun than full water butts.
Tip: use plastic watering cans and buckets, as the changeable weather can rust metal tools left outside.
4: Clear out any stakes, supports, and summer trellising
This is probably the easiest task, but also one of the most important cost-saving tips for any gardener: tidy up. Leaving bamboo canes, tomato cages, metal trellising, or plant supports in the ground over winter can damage them, and timber supports will rot faster in the ground than in the shed.
5: Mulch raised beds before the first frost
Current climate change patterns in the gardens seem to be pushing the first frost earlier and earlier. This year, ours was late November, last year it was the first week in December. When we bought the house, ten years ago, the first frost didn’t hit until just before Christmas!
As a basic rule, mulch well in advance of any frost, and don’t leave it too late. Mulching frozen soil insulates cold, while mulching warm soil insulates heat. Simple.
6: The best mulches to feed no dig raised beds
Mulch can be everything from cardboard and newspaper to fresh manure. Because mulch has a few uses, it’s important to understand them. In the step above, anything that covers the soil, from cardboard to tarpaulin will do. But, to make the most of winter, consider some of the mulches below to truly enrich and feed your soil.
Compost is the easiest mulch to use, and good homemade compost is completely free. Mixed compost (green and brown materials) is packed with nitrogen, potassium and carbon. A minimum of 2” of mulch each winter on your raised beds will be worked into the soil with no need to dig, in time for planting in spring.
Rotted manure is the richest mulch you can use, with huge amounts of nitrogen, and small amounts of urea to maintain a healthy pH. Aside from actively warming the soil, rotted manure will introduce naturally healthy bacteria, as well as red worms and other insects to the soil, but be sure to check for weeds in early spring!
Tip: It takes around 6 months to rot manure to a safe level to grow crops, so if you plan on sowing, or planting into the beds in May, fresh manure is fine.
Leaf mold is really simple to make and really handy for no dig gardens as it is quickly worked into the soil by worms, and doesn’t have a particularly high nutrient content. That means you can feed plants in spring with more considered fertilizers, depending on individual needs.
For empty winter beds with poor soil structure, leaf litter is the best option. I prefer using leaf litter to leaf mold in winter, but there is a significant downside… it’s far less insulating. Leaf litter will work into the soil quickly and encourages worms to produce more worm castings (Vermicompost). That natural process will help to maintain a reasonable temperature, but not enough to grow in.
About ten years ago, I was talking to an allotment holder, about mulches. He said one of the wisest things I’ve ever heard: grass is just manure without the goodness taken out. Rotting grass is rammed full of nutrients and nitrogen and, as it rots, it allows carbon transfer into the soil.
The minerals and moisture in the grass are easy for worms to break down too, and, above all else, it’s completely free. If you store grass clippings separately from other compost, you can use them throughout the year to feed raised beds.
And, if that wasn’t enough, it heats up as it rots, so by mulching your raised beds with 3-4” of fresh grass clippings in early winter (the final cut of the year) you’ll keep the soil warm, have the perfect soil for potatoes the following spring.
Grow cover crops, or green manure
Cover crops and green manure makes use of beds over winter and helps to replenish soil structure. However, unless you cut back, compost, and reapply the green manure to your beds it requires digging, so isn’t strictly part of a no dig gardening plan.
The other downsides to green manure are that it won’t insulate your soil, and needs sowing in early to mid-fall to have the best effect.
7: Cover your no dig beds
Even if you don’t have a greenhouse, there are plenty of ways to heat the soil, and insulate any overwintering plants like brassicas and salad crops without a full structure.
The easiest way to cloche an entire raised bed (for preparation and storage) is with fleece:
- Bend two lengths of sturdy wire, or plastic pipe, into semi-circles, and insert each semi-circle at the end of a bed.
- Connect them with long bamboo canes.
- Secure horticultural fleece (or polythene) to the structure.
It’s that simple and can extend salad crops like spinach and radish right into December (or January if you water with warmed buckets, as above).
8: Protect your tender plants
In milder climates, it’s possible to protect some tender plants like citrus trees without bringing them indoors. Any cloche you can find or build will work to protect them from snow and prolonged frost. Wrapping them in fleece works just as well too.
9: Divide bulbs and tuberous vegetables
Jerusalem artichokes, sweet potatoes, and perennial onions can be divided in early winter. Simply digging out half a clump and moving it a few feet across before the frost hits will mean a better harvest next year.
10: Cut back any half-hardy herbaceous perennials
Half-hardy herbaceous perennials, including most Mediterranean herbs, should be cut back. Sage, thyme, and oregano need to be cut to 2-3” above ground level to encourage new growth next year. Hardy perennial herbs like rosemary don’t need protection but should be pruned to the lowest green leaves to maintain a good size.
11: Clean any timber panels
Once you’ve sorted the growing space of your no dig raised beds, it’s time to do the boring bits. Scrub any timber boards around raised beds with soapy water and a stiff brush. This might sound excessive, but timber boards will rot eventually, and cleaning off any lichen, mold, or grime will extend their life by several years.
12: Refresh paths between no dig beds
The paths between raised beds are just as important to manage. Weeds will grow between paving slabs and poke out from wood chip. Scrape back any rotten wood chip and add it to your compost, then replace the whole lot with fresh bark.
For reasonably new paths, just remove any perennial weeds and seed heads that might spread around in spring.
13: Prepare compost for spring
And finally, use every single ounce of organic matter removed from your raised beds to create a fresh batch of starter compost for next year.
Raised bed gardening is rewarding and easier to manage than most traditional methods of vegetable gardening. Adding no dig to the mix just means that you can be truly organic, and focus on the things that matter, like soil enrichment, and crop health.
For any gardener looking to start a new project, we’ve got plenty of guides on garden structures and how to get started with no dig systems. For those of you already on the journey with us, stick to the guide above, and tweak it for your own garden to prepare your own raised beds for winter.