As Charles Dowding readies himself for the autumn harvest, he explains that now is also the time to make the best compost from a variety of sources
With Charles Dowding
This mellow season of mists and harvests also offers many ingredients for making compost. After a dry summer that was frustrating for its lack of green material, now we can get busy with filling compost heaps right up until Christmas.
Above ground harvests
Many leaf harvests continue into winter if the weather is mild, especially kale, spinach, coriander, land cress and chicory/ endive. Frost does not kill these plants, but it slows the growth of new leaves, which also become smaller because of poor light levels. The darkness of days in a UK winter is at least mitigated by the gulf stream, which usually maintains temperatures at a level where some growth occurs, including weeds.
Some vegetable leaves are not frost hardy and need harvesting before it turns cold: celery, Florence fennel, dill and hearts of brassicas Chinese cabbage are examples. You can store hearts for a few weeks in cool, damp conditions.
Below ground harvests
Apart from potatoes, root vegetables survive slight and even moderate frosts, say to -3°C, depending on how long the frost lasts. Beetroot need watching because they are partly above ground and therefore more exposed to cold. I usually harvest them all in November. Root harvests also provide a decent amount of leaves for the compost heap.
Winter salad leaves
Growing plants in a polytunnel, greenhouse or under the covers of mesh and fleece enables extra growth of precious winter leaves. There is even time, if only just, to sow the fastest growers: salad rocket, mustards and mizuna. A better option is that you remembered to sow them in September and have plants ready now, including lettuce, endive, spinach and land cress. Or you could buy some plants. Check out www.organicplants.co.uk.
Salad leaves in winter are extra precious, so make the most of any unused spaces undercover. I use greenhouse staging that is not needed over the winter for plant raising, growing salad leaves in mushroom boxes, as in the pictures ( right). Fill to the brim with multipurpose compost, packed well down
to ensure the maximum amount of fertility and moisture for growth all winter, then plant six of any winter salads in each tray.
Be careful not to overwater. When growth is slow and air is humid from December to mid February, I find that watering as little as once a fortnight is sufficient. Check the weight of each box before giving water and, if it is heavy, wait another week.
Six plants per box may look too few at first, but they have the whole winter to grow and for their roots to explore all the compost. You can take harvests every two weeks or so and it is important to pick larger outer leaves rather than cutting across the top. This means that you keep the smaller heart leaves intact. These are the engines of new growth: they do more photosynthesising than the older, larger leaves which you twist or cut off to eat.
The principle is the same with de-leafing the lower leaves of tomato plants in the summer months. They contribute little to plant growth, compared to the top leaves that are working hard.
Compost for long-term fertility
Compost is any decomposed material, from crop wastes, weeds, tree leaves and straw to animal manure with or without bedding. On a smallholding you may have enough manure to run an abundant vegetable plot, but it is rare for the wastes of a vegetable garden alone to generate sufficient compost to grow great veg.
I source wastes from other businesses, including a couple of local cafes, and I’m impressed with how much coffee they supply for my heap. It amounts to around 80kg/month, which adds up to a tonne each year. Coffee grounds are 3% nitrogen and pH 6.8, and are better composted to break them down rather than spread on the ground where the coffee will go mouldy during its breakdown process. I also find that it doesn’t discourage slugs.
Other waste materials I look out for are sweepings from a local stable yard, cardboard, egg boxes from a restaurant, crumpled paper and vegetable wastes from a local greengrocer.
From waste to compost
Last autumn I filled a heap 1.5m square from late October until Christmas. I regularly added enough new material to maintain a temperature in the heap of 50-60°C, a heat which kills weed seeds and speeds breakdown.
The roof over my heaps helps the process by keeping out cold rain, which otherwise makes compost soggy and reduces the oxygen content. If you squeeze a handful of compost or manure and more than two drops of water fall out, it is too wet. Therefore, it is worth providing cover for heaps and black polythene is useful if you don’t have a roof.
For me, come December the local rats had moved in and were making a mess outside the heap as they moved material out to make their runs and nests. I am not comfortable with rats, but accept they need a winter home and I appreciate their discretion as they are private creatures and I rarely see one. In a compost heap they actually do good aeration and mixing. This became apparent in March when I was fortunate to have a willing visitor who offered to turn the heap. Turning means mixing and shaking out the lumps during the process of moving the whole heap onto an adjacent area after removing the least decomposed top layer to the current compost heap. Turning also encouraged the rats to depart for summer quarters in nearby fields.
We were so impressed with the lovely compost. And then it got even better after I covered the heap with black polythene from a farmer’s silage clamp. Worms love the darkness and moisture under polythene and they multiplied fast, turning the heap into a giant wormery. The only downside is that with every passing month, the heap shrinks in volume, although it’s goodness is becoming highly concentrated.
Why add compost?
People sometimes say: “I couldn’t practice no dig as I don’t have enough compost.” However, I notice on the dig/no dig trial here that with the same amount of compost, harvests are consistently higher from the no dig bed. Both beds give a lot of harvests, averaging 100kg from 7.5m2, and that’s after adding 5cm of compost every autumn. Now is the time, replicating leaf fall in nature.
The compost heap recently finished and with the front removed
Four-month-old compost being turned in March
Charles dibbing holes for winter salads which will be covered with mesh
Lettuce and mustards just planted into boxes filled with multipurpose compost in mid- October
The same salad boxes as left in mid-March. They have given 2.1kg of mustard and lettuce leaves
Before harvesting beetroot for winter you can pinch out the heart leaves for salad