Updates from April 2012.
April’s first half has turned increasingly cold, even as the sun rises so rapidly. We are still not out of the woods as the wind will probably come more from the north than from the south in April’s second half. Normally at this time I remove fleece from lettuce, but am in no rush to do so this year – although plants have grown well, after the warmth of late March especially, and some outdoor lettuce, growing under fleece, are nearly ready to pick a few leaves off.
Over-wintered salads in the tunnels have grown sensationally through the past month with some of the healthiest, glossiest leaves one could wish for, and in greater quantity than I have known before. I think this is down to a combination of extra sunshine and increasing soil fertility. Once a year, in each of the last two springs, I have put a good two inches of well rotted cow manure on my tunnel beds, as well as a twice yearly application of biodynamic preparation 500. On some of the beds I also spread some volcanic lava meal, but have used no other liquid or solid fertilisers to grow all the summer vegetables such as tomatoes and basil, from May to October, followed by winter salads from October to April/May
Over the coming month under cover, as the winter salad plants start to flower, they are twisted out (along with any tiny weeds), then manure is spread and plants can go in when ready. This will be in early to mid May for tomatoes (currently in modules and ready to pot on), mid May for basil (seedling stage at present), late May for cucumber and melon (I only just sowed them!) and early June for a few aubergine and sweet pepper.
I like to water thoroughly before spreading manure, to have moist soil for planting, at which point I can assess with the planting trowel how well I have been watering, whether moisture levels are good. I mostly work out the need to water by how plants are looking and growing, then the planting stage is a chance to physically see how damp the soil is. Currently I am watering every four days or so, with salads growing so fast. This gives enough and also allows time between watering for both plants and the soil surface to dry out, which limits slug numbers, weed germination and mildew on leaves.
Outdoors there is less sowing and planting unless you are still waiting to plant calabrese, Boltardy beetroot, lettuce, parsley, peas, onion sets (quick!) and potatoes. Also you can still sow parsnips, early carrots and spinach outdoors, but broad beans should be in by now, and overwintered beans are flowering, while many overwintered cabbage are making small, sweet hearts. A few of my cabbage have bolted before hearting, mainly Pyrmaid F1 which I shall not grow again! Most kale is flowering and the shoots are tasty; also I am picking lots of leaves off the perennial kale and their sweetness is impressive.
Indoor sowings in April’s second half include squashes, courgette, basil, celery and Brussels sprout; celeriac should be up and pricked out, for planting before end May. I advise waiting until early May for first sowings of French bean and sweetcorn.
Weeds are germinating but not racing away in the cold. Any dry days are useful for hoeing and it is good to hoe almost before weeds become visible: try rustling your fingers through a few areas to see if they disturb any germinating weed seedlings, with tiny white roots. If there are a lot of these, a shallow and very quick hoeing is worthwhile.
There has been lots happening in March, more than usual. Garlic, spring cabbage, spring onion, broad beans and kales have grown beautifully, and my tunnel salads have been hugely productive, reflecting also the increasingly fertile soil. As well as abundant salads, this soil is growing almost no weeds, making the whole experience really enjoyable: the only weeding needed in my tunnels is to pull out odd small weeds while picking.
Outside, the dry weather has curtailed early weed germination but an early hoeing may be necessary if you still have residual weed seeds.
After the incredible warmth of late March, April’s first half looks cold, perhaps as cold as anything in winter except for that spell in early February. Nights will be frosty and it was interesting to notice how cold the nights were during the heatwave in March: we had 18-20C by day followed by grass frost every night, a reminder that we still need to be careful of sowing and planting any heat-demanding vegetables such as courgettes, summer beans and sweetcorn. They all require constant warmth, and can only be grown undercover at this time of year in the warmer parts of Britain.
Celeriac should have been sown in March, indoors in a small seed tray or pot, for pricking out in April and planting in May. Sowing now is possible, but don’t delay. Basil, cucumber and melon can be sown undercover, and germinated in some extra warmth for best results.
In the greenhouse I have made a small sowing of French beans to plant in a polytunnel around mid April, and of courgettes to plant outside at month’s end, covered with a cloche of two layers of fleece. This worked well last year when May was generally colder than April, with cool winds that summer vegetables did not like, and also we had cool nights in June that prevented early growth of many outdoor beans, sweetcorn and squashes. So bear all this in mind when tempted to make those early sowings.
On the other hand, vegetables such as lettuce, spinach, peas, onions and spring onions, carrots, cabbage, cauliflower and calabrese survive almost any spring weather. Overwintered broad beans are flowering, offering delicious scents and a hint of welcome harvests in the hungry gap of May, although their early flowers may be frosted off. Beetroot sown in February in modules, planted under fleece in late March, is starting to grow, but this only works for the variety Boltardy. Many beets are sensitive to cold nights, not in the sense of being killed by frost, but of being encouraged to flower before offering much harvest. So I advise waiting until late April for sowing most beetroot, and chard too; ruby chard is especially prone to bolt when sown too early. If you have made an early sowing, and you want chard later in summer and autumn, I would sow again in June.
For true spinach (not leaf beet) the pendulum is swinging in the opposite direction as March sowings are now growing nicely and should continue for many weeks, while sowings in late April and May will give less pickings before arriving at the main flowering season in June. Sow as soon as possible if you have not already. I sow spinach in February and March mostly, then in August, and never in May or June.
Tomatoes should be growing strongly and need potting on in April to give them enough space and compost to make big, early plants for setting out any time from late month. Greenhouses can be planted earlier than tunnels as glass conserves more heat at night than plastic.
Potatoes can be planted any time in April, but early potatoes should be in by now if you live somewhere with less late frost. Ideally you want them to put down strong roots and then emerge some leaves after the last frost has happened. Not knowing in advance when this may be makes early potatoes a bit of a gamble: earthing up with soil and/or compost helps protect them, before nights when frost is forecast, more effectively than fleece which is best held above leaves if possible, as frost damage happens where fleece is in contact with any leaves.
Peas do not mind spring frosts and should be growing away now. I have photos here to show how you can pick pea shoots, for some lovely pea flavour in spring salads. The more shoots you pick, the less pea pods will grow, so I dedicate an area to peas planted 9” apart for shoots, separate to a bed with wider spaced pea plants for pods.
April sees the last harvests of most overwintered vegetables such as kale, savoy cabbage, leeks and parsnip. Then in May we shall be waiting and watching for first harvests of March sown beetroot, carrots, hearting lettuce, peas and broad beans, which mostly occur in June. May is the hungry gap, after winter vegetables have finished and before spring ones are ready. You can avoid it by sowing spinach, spring cabbage and spring onion in late August and broad beans in November. Perennial vegetables also come into their own through spring: seakale and asparagus start cropping after mid month and rhubarb is producing lots of stalks already, except for late varieties. Rhubarb is a thirsty, fast growing plant and likes any water you can spare. Or perhaps it will have rained when you read this?