So, it's nearing September and, whisper it, nearing the possibility of frost (yes, of course we know summer only arrived last week). But it is time to at least to start thinking about lifting some root crops and whether or not to 'clamp'? And of course, time, too, for more advice from Caroline Foley.
I hate to mention it, but by the end of September it is wise to be prepared for the likelihood of frosts. So crops that are not frost hardy needs to be ripened up, brought in, protected against the cold or harvested. If your soil is well drained, you can leave carrots in the ground until they start to sprout again in the New Year, though in my experience they coarsen over time. Parsnips are usually left in for a month or two as the first light frosts improve the flavour. Avoid over-handling root vegetables when you dig them up. With luck and given a dry day, the soil will just fall off and they can be stored unwashed. If you have heavy clay that sticks, or if you suspect any damage or disease, then it's better to wash. Either way, twist off the foliage leaving a small topknot. Take particular care with beetroot as it 'bleeds'. You can either store them in crates with sand in between the layers or make a clamp.
Building a clamp is rather like making a giant mud pie and is just as satisfying. A time-honoured practice, it keeps the produce fresher for longer than conventional storing and makes good use of allotment space in winter. Clamps can be cone shaped, but a low rectangular shape along the lines of a roof ridge is more practical. You can chip into it to raid the stores, without danger of structural damage, and it's easy to seal it up behind you. Choose a sheltered spot with well-drained soil. Mark out the area and dig a small trench around it for extra drainage. Lay down a bed of sand with some bran or wood ash around the edge to deter slugs. Only store perfect specimens as a single damaged or diseased one could wreck the your entire precious cache. Build a castle of roots, laying them down in rows, with the largest at the bottom and smallest at the top. Aim for a pitch of 45º. Cover generously with straw or dried grass for insulation. If you can get it, wheat straw is the easiest to work as it's naturally straight and rigid. Lay it on vertically and tie the ends up in a topknot. If it's a long clamp, you may need two or three at intervals. The topknots will poke out of the clamp and act as 'chimneys'. To finish off, pack soil into the crevices working from the bottom upwards until you've covered the whole thing quite thickly, 15- 20cm (6 - 8 ins), with mud and made it into a solid earthwork. Compact it with the back of a spade for good measure. The RHS has good avice on storing root veg here.
Get the last of your potatoes up and store them in the dark - ideally in potato sacks if not in the clamp. Finish harvesting onions and the last of the globe artichokes.
Remove the stakes and lay cordon tomatoes down on a bed of straw. Cover them with cloches or fleece to ripen them. If you still end up with green tomatoes when the frosts come, bring them inside and put them in a draw, cardboard box or brown paper bags with a ripe tomato, or even better, a blackening banana. The ethylene gas that it emits should do the trick. Alternatively, you could make green tomato chutney.
Though usually treated as annuals, chilli plants are perennials. They can be grown on through winter on a sunny kitchen windowsill and put out again next summer.
Test marrows, pumpkins and squashes for readiness by prodding the skin with your thumbnail. The skins feel hard when they are ready. Pick them with some stalk and leave them in the sun or indoors in the warmth, for another couple of weeks. This will 'cure' the skin further and help them to store for longer. After that keep them in cool, dark, dry place and they should last until Christmas.
Pot up mint, chives and parsley and bring them in to extend their season.
Cut down asparagus foliage.
Harvest time produces loads of green material for the compost heap. So it's an ideal moment to get a really a good heap going, clearing the allotment as you go.
Cover the pond with netting to stop leaves blowing in.
Make leaf mould for free, top quality potting compost, soil conditioner and mulch. A nifty way to catch leaves, if they are blowing your way, is to put up a low windward barrier of netting. Chopping them up by shredding or mowing (preferably with a rotary mower) speeds up the process. Tie them up in polythene sacks with holes to let in water or make them a cage of chicken wire. Apart from watering them from time to time in dry weather, you can then forget about them for a year or two. The length of time it takes for them to rot down depends on the leaves. Oak, beech and hornbeam leaves are probably the fastest, usually taking a year to 18 months.
Footnote. As you clear the leaves you may come across colonies of snails to gather and feed to the ducks. I was interested to discover that at last a use has been found for snail slime. You can put it on your face. Though the association is off-putting (to say the least), the health shop, Holland and Barrett, are marketing De Tuinen Snail Face Gel. The story goes that snail farmers in Chili noticed that their hands had became wonderfully smooth and soft. Subsequent research revealed that snail excretions contain collagen and other skin enhancing properties
