Tag Archives: polytunnels

Guy’s Newsletter: tomatoes, badgers & bees

Last week we picked our first tomatoes of the year; all being well, each of the 15,000 plants will produce 3kg of fruit between now and September. These tomatoes are actually later than we planned; with so much sunshine recently it’s easy to forget that it was quite a cold spring. The only way to harvest any earlier would be by heating our polytunnels through burning fossil fuels on a huge scale. However much we’d like to support year-round local tomato growing, our environmental study with Exeter University (see http://www.riverfordenvironment.co.uk) suggests that in terms of carbon footprint, it’s many times better to truck (not fly) out of season peppers or tomatoes in from Spain where they do not require heat, than grow them here under heat, as the data below suggests. This was always my instinct and since completing the research, it remains our policy. It makes marketing tricky as simple messages are the most effective; but in reality, buying British tomatoes year-round is not as green as it sounds.

CO2-emissionsTo aid tomato pollination, we introduce bee hives into our polytunnels every summer. Last week, when the tunnel team started work at 5am they found the hives moved around, upturned and eventually destroyed. Paranoid theories about vandals proliferated until we realised that, as with our occasionally trashed sweetcorn and pumpkins, the omnivorous badger is to blame. It astounds me that they can eat live bees without ill effect but a quick internet search shows that it is not uncommon. We have now suspended our hives from the roof and set up a motion activated camera; keep an eye on our Facebook page for a video of the culprits.

Guy Watson

guy’s newsletter: plants, pests & the search for balance

The first basil and cucumbers were harvested from our polytunnels last week, and very fine they were too. We grow mainly mini cucumbers as they taste better, are easier to grow and avoid you having that soggy-ended cucumber half lurking in the back of the fridge, so I can’t really understand why anyone grows anything else.

Outside we are in the hands of the Gods with a difficult start to the season, but the protection of our flimsy tunnels can give dangerous delusions of omnipotence. We can manipulate the temperature, humidity and ventilation to promote growth and avoid fungal disease and our team of pickers, pruners and tomato trainers are experts at identifying and monitoring aphids and spider mites. Rather than turning to chemicals as a means of pest control, a dynamic balance of pests and predators is our aim, but when an aphid gets its proboscis plugged into a good stream of plant sap they can squeeze out babies at an alarming rate. If life is good they give up on sex and egg production altogether; why bother with the complications, wasted energy and variable offspring when you can just replicate more like mamma via parthenogenesis. The trick is to introduce enough of the right predators and parasites before the explosion happens and to get the balance at an acceptable level where crops do not suffer significantly.

We are struggling to find that balance out in the fields too. Aphids in the lettuce and flea beetle on rocket, mustard and spinach have forced us to abandon a number of crops, just when we need them most for your boxes. It could be that low temperatures are disproportionately slowing predator activity, but I feel more inclined to attribute our problems to stressed crops emerging from a miserable winter. Just as with humans, stress leads to vulnerability. Later crops are looking happier however, and past experience would suggest that predator appetites rise with temperature faster than pest fecundity does. So, as we enter summer proper, we expect the balance to come outside in our fields as it has in the tunnels, and all will be well on the farm (for the time being at least).

Guy Watson

redemption at last

After two long winters, separated by the farming disaster that was last summer, followed by a late spring, it is hard to remember what abundance feels like. Many growers felt forsaken, with a mounting suspicion that they would never see a full and healthy crop again. To walk the farm this morning, bathed in sunshine, through one field after another of strong and healthy crops is blissful; I almost have to pinch myself to be sure it is not a dream. To once again be surrounded by a wealth of broad beans (first pickings are in the boxes this week), spinach, beetroot, potatoes, lettuce, onions and a multitude of baby leaf salad is truly joyous. In the polytunnels we have been picking cucumbers, basil, French beans, salad onions and are now starting the first tomatoes; all are looking fantastic. First pickings are often not the best but, to add to the joy, this year the flavour of most crops is wonderful.

My one sadness is walking the strawberry field; they taste great and it’s a good crop but this will be our last year of strawberries. After 25 years of experimentation and obstinate determination to grow them outside, we have conceded defeat. In our climate the only way to produce strawberries with any degree of reliability and economic viability is in polytunnels; others reached this conclusion years ago and 95% of the UK crop is now grown under cover.

Such stubbornness must run in the family. For 50 years my father made his money milking cows in a fairly conventional manner, and lost much of it keeping pigs unconventionally. His restless search for a system that respected their intelligence and natural instincts failed; we now buy our pigs from Helen Browning who, on better drained land with lower rainfall, has succeeded.

Perhaps we will put up our own strawberry polytunnels at some point but for now I cannot face the battle with planners, so our strawberries will be grown by Angus Davidson, a specialist organic producer in Hereford. I have not given up entirely, but after losing so much fruit to Botrytis in recent, damp years I’m happy to let someone else take on the strawberry struggle, for now at least.

Guy Watson

La terre est engorgée

This is coming from France where the soil is ‘full to the throat’ and has been since June – it has almost been as wet as in Devon. In response we have our brand new, two acre, large football pitch sized tunnel which is already planted with 40,000 lettuces plus chard, spinach and pak choi. All should be in your boxes in March, two months ahead of the UK season, helping to fill our ‘hungry gap’ and to give you relief from parsnips and swedes. After less than a week the roots are reaching out into the soil and the leaves are putting on new growth. The Vendée is only marginally warmer than Devon at this time of year, but there is much better light, allowing the plants to race away, while in Devon they would just sit waiting to be eaten by slugs. As soon as the lettuce is cleared we will be planting ramiro peppers which will be in your boxes from July to October before replanting another two crops of salad for the winter.

Outside, the skeletal remains of last summer’s disastrous pepper crop is still hanging around to depress me. It has been too wet to plough in the memory of botrytis-ridden fruit, so there it is, everyday, reminding me of my folly and pig-headed stubbornness in trying to grow crops outside when everyone else has moved them under glass or plastic. In the best years outside, crops might have better flavour and possibly less environmental and aesthetic impact. Given the reality of climatic change and resulting risks, it is economically unsustainable, environmentally dubious and emotionally disastrous to continue outside. How many more of my dogmas will I be forced to swallow?

I love my new tunnels. Outside, the soil may be full to throat, but in here it can be controlled at the push of a few buttons. The interlocking cathedral-like arches encourage feelings of omnipotence. Have we conquered the elements? Computer-controlled irrigation and ventilation encourages dangerous feelings of power and influence and
I must remind myself that a hurricane, attack of mildew or plague of aphids could still lay waste to my plans.

Guy Watson

Surfing & cauliflowers

We opened the large tunnels fully last week and just let the gale blow through. No flimsy polythene was going to stop that wind. The tunnels survived and the winter salads looked a little windswept but none the worse for the experience. A smaller tunnel was shredded but we are counting ourselves lucky.

Outside, we have given up harvesting roots until the deluge abates. Boxes are being filled from store using roots scheduled for later in the winter. Harvesting above ground, the green stuff is challenging enough – just getting the crop to the field gate is taking determination and ingenuity. The greatest merit of a tractor this year seems to be how high the air intake is and what depth of water it can tolerate before sucking it in and dying. To see an extreme example, visit the Riverford Facebook page where there is a photo of our neighbour and co-op member, David Savage making sure savoy cabbages make it to the veg boxes. I reckon I could surf on the bow wave from his tractor.

When the rain stops I am still heartened by how quickly our fields drain and become passable again provided we have not damaged them by travelling in the wet. Organically farmed land will normally have a better, more open structure which allows water to percolate down to the subsoil more quickly. The channels left by earthworms help tremendously.

The crops themselves are not looking so bad and our cauliflowers are finally getting going. Local wisdom says they hate having ‘wet feet’ but, although they are smaller and later than usual, they look like they will make a fair crop. Traditionally, winter cauliflowers are grown on the coastal fringe of the South West, where they are protected from winter frosts by the moderating influence of the surrounding sea and are fertilized with seaweed dragged off the beaches below. Different varieties are triggered by a mixture of day length and temperature to switch their efforts from leaf to curd. The result is that, though we plant all our cauliflower in July, we cut them over eight months from October to early May.

Guy Watson

The joy of tunnels

For years we agonised over whether the benefits of tunnels (earliness, quality and cropping reliability) justified the eyesore. Last year we took the plunge and covered three acres of our best land with polytunnels, doubling our area of protected cropping. Despite the lack of sunshine, these three acres have been the most prosperous on the farm this year, providing good harvests of winter salads, tomatoes, cucumbers, beans and peppers.

We are now harvesting the last of the sakura, sassari and cheramy cherry tomatoes and should be picking these for another week. Unfortunately we’ve had to abadon the larger dometica and mecano tomatoes which have now lost their sweetness and are showing ghost spotting due to low levels of botrytis.

There is always a lot of green fruit which will not ripen by the end of the season. This will be picked and made into chutney by my brother Ben (sold in our farm shop), or perhaps by you. From today, green tomato chutney kits are available to order, complete with a recipe and ingredients, www.riverford.co.uk/chutneykit. There is nothing like a well stocked preserve shelf; it makes me feel ready for winter and prepared for any forgotten presents.

As the cucumbers and tomatoes are cleared we are cultivating and replanting the tunnels with rocket, mizuna, claytonia, baby leaf lettuce and chard, for harvest through the winter. Outside, most of the autumn and winter crops have established well and in the dryer east are going into autumn as we would like. In the wetter west we continue to suffer from a combination of low light levels and leaching carrying soluble nutrients beyond the reach of our crops roots, but we stay optimistic.

Guy Watson

pumpkin day – free family day out
Saturday 20th October Mole End Farm, Kent
Saturday 27th October Upper Norton Farm, Hampshire; Sacrewell Farm, Cambridgeshire; Wash Farm, Devon
Sunday 28th October Home Farm, Yorkshire

Biological warfare

With a cold wet summer such as we’re experiencing this year it can be a bit of a relief to go down to the polytunnels where it’s nice and dry and we have much greater influence over the growing environment. These warmer conditions can bring problems of their own, however, as what is good for something like a cucumber can also be good for pests such as aphids and red spider mite, which can rip through a crop if nothing is done about it. Aphids have a life cycle of 3-4weeks (depending on climatic conditions) and during that time can give birth to 40-100 live young who emerge with the next generation already inside them!

Some predators will follow these pests through the doors: ladybirds, lacewings and hoverflies are all welcome visitors and we have some plants dotted around to encourage them (lacewings love fennel, for example) but this isn’t always enough and so we boost their numbers by distributing extra pest-specific, insects and bugs through the crop.

These fall into two main categories: predators and parasites. Predators (like phytoseiulus persimilis for red spider mite and aphidoletes aphidimyza for aphids) will attack and eat the pest, then lay eggs which hatch into a new generation to continue the process. Parasites are, if anything, more gruesome: aphidius colemani, for example, will lay an egg inside the aphid itself. This obviously kills the pest as the larva grows and when it hatches, carries on the process. Parasites tend to be much more host-specific than predators, which aren’t too fussy (within reason) what they go for. In both cases, the second generation tend to be more active and vigorous than the parents we introduced as they are more acclimatised to the conditions in the tunnels.

Some battles you win and some you lose: to date there are no signs of red spider mite, but our peppers have a few green aphid and one of our cucumber tunnels is fairly heavily infested with black aphid. We have ordered extra insects to help in the war and I have even been introducing the odd ladybird I have found in the fields! Hopefully this will be enough and we can get on top of the problem.

ImageBack outside, meanwhile, we are beginning to harvest our globe artichokes. These highly architectural plants, a relative of the humble thistle, are one of the many crops to have taken a bit of a battering from the elements: they can suffer from browning leaves if conditions are too humid but are worth persevering with as they’re relatively low maintenance for a perennial crop and have a great and unique flavour. I tend to just steam them and eat as a starter with loads of melted butter, though I’m sure Rob in our Field Kitchen restaurant has far more imaginative uses for them…

Ed’s Farm Blog – Springing into inaction

wet garlicOur early season crops are usually planted in fields across the valley from us, as they are broadly southfacing and warm up quicker with well-drained soil to allow early planting. As these can’t be irrigated we rely on the usual April showers to water them for us. Last year the long dry spell actually meant that some of the lettuce got stressed, bolted, and we lost a fair amount of the crop. Not this year! Below average temperatures mean that the crops are growing more slowly than hoped, but there is certainly no lack of water.

Continual rainfall such as we are experiencing at present brings its own set of problems, however. At this time of year we would be frantically planting, fleeceing, brushweeding and hoeing our lettuce, spinach, summer greens and so on; but not now. The fields are simply too wet to cultivate and a short break in the weather is little help as they need a minimum of 2-3 days (sometimes more depending on the soil) to dry out enough to work.

Fortunately for our staff there has been plenty to do in the polytunnels: Manuring, putting up supports for tomatoes, and plenty of hand planting. But as this begins to draw to a close we can forsee a few quiet weeks ahead whilst we wait for the crops we have to come on and pray for a break in the weather.

On the up side our wet garlic is looking good; this was planted as individual cloves that we broke up from whole bulbs in late October and early November. The two varieties we grow are Germidor and Messidrome as they produce large cloves: and usually the larger the clove you plant, the larger the wet garlic you produce.

So a mixed spring so far. To quote the philosopher from Morecombe, “bring me sunshine…”

Ed’s Farm Blog – loo roll in the polytunnels

Ed's Farm Blog - Organic SaladI’m Ed Scott, and I work on the Riverford Organic’s founding farm in Devon. The plan is that I’ll be writing a regular farm blog, showing you what we’re growing and how we’re growing it.

It’s now the beginning of February, and we are busy picking leeks and the last of our curly kale from the fields. We have also just laid the last of our winter salad pack in the polytunnels. The majority of our salads are block-planted through a plastic mulch, and treated as ‘cut-and-come-again’ crops; these can be picked between three and five times, dependant on type and variety.

As well as the blocks, a proportion of our salad leaf plants come in seed matting; a large spool of seeds sandwiched between plastic and a blotting-paper like material. Much like cress grown on loo roll at home, upon germination the roots reach through the paper into the soil below, while the leaf pushes up through tiny slits pre-cut in the plastic. This system has the advantage of lower plant and planting costs whilst ensuring the crop is not swamped with weeds; and although we have mixed feelings about the volume of plastic used, it’s actually no more than that used in our traditional block planted system.

TEd's Organic Farm Bloghe disadvantage of this system is that the seed matting doesn’t work with all plants and can only be cropped once; our first planting went in during October and was harvested in the run-up to Christmas. The rolls laid this week should be ready for harvesting in late March. Keep an eye out for further pictures showing progress through the growing stages.

Ed Scott
Assistant Harvest Manager

Strawberries and poly tunnels

Thanks to the 50 or so of you who responded to my musings on whether it would be a good idea to grow at least some of our strawberries under tunnels to protect them from the weather and consequent losses (newsletter of 14th June.) The original post is Strawberries at Wash Farm in Devonhere.

There was a (very) small majority who felt that the eyesore was justified by benefit but is was a close thing. My views have changed over the years from being very anti tunnels to thinking that they are justified for intensive crops like strawberries. We will do some costings to check that it makes economical sense and the final decision will lie with our suppliers; in Devon that, means John, the farm manager. If it works economically we will not discourage it as we have in the past.  

Responding to a few specific points raised in the responses

  • An acre (originally defined as the area that one man could plough with one horse in a day) is 4000 square metres; 15 time the paying area of a tennis court or just over half the area of a premier league football pitch. So to supply all our 60,000 customers with strawberries would require about 8 acres of tunnels or about 5 football pitches.
  • Extending the season; there was an over whelming majority who felt that tunnels were not justified to extend the season. Most people were happy to have a relatively short “natural season”. Tunnels can extend the season but this would not be our motivation; we and you seem perfectly happy with it as it is.
  • The plastic lasts 3 to five years and would be recycled after use
  • The plastic is usually clear and would appear white but some people have successfully used green. I am not convinced this is an aesthetic benefit.
  • On flavour: My views have changed from a prejudice against tunnels as promoting lush growth and reducing light levels and therefore flavour. In practice we find that the best flavour comes from the plants with the best growing conditions. We often get unpleasant off flavours when plants suffer stress. I suspect that on average the fruit would be better from under tunnels.

Hope that is interesting

Guy