I think that anyone reading this will be feeling some
sympathy for our American friends who may have been affected by Hurricane
Sandy. It’s risky enough being a grower without “Super Storms”.

Frost damaged Elsanta strawberry crown after Winter 2010-11, UK

Growers of table top strawberries face a particular  challenge if they decide to over-winter a crop instead of replanting in the Spring. The compost filled troughs, pots or bags are exposed to un-relenting  chill if left on the table structure.

There is no moderating effect of the surrounding soil – something that prevents severe crown injury in conventional  fields in all but the coldest districts.

Furthermore, any blanket of snow does not  prevent heat loss from beneath the containers. In Britain, growers are advised  to move containers off from tables and onto the floor if night temperatures below -8^oC  (46^oF) are expected.

Roots of Elsanta plants damaged by a combination of freeze injury and phytophthora

This is expensive on labour and exposes the plants to soil borne pests and diseases, perhaps especially Phytophthora fragrariae. If the plants are then covered with fleece, Botrytis and aphids can be difficult too.

Possible Solutions

• Wrap the containers in fleece (row cover) in situ. This has limited benefit if
  freezing conditions persist for many days.
• Convert to 4-season tunnel structures. Under a
  tunnel the wind chill factor is massively reduced and fleece is easier to
  manage. Maybe a heat source can be made available for extreme events.
• Haygrove have developed a patented telescopic
  table top system so that tables can be lowered and raised quickly.

Telescopic substrate system, Autumn 2011, in the "up position".

Northern, temperate zone berry growers are busy with tunnel doors at this time. In England some have belatedly decided to install temporary doors now that the weather has changed. We had Californian weather for March but we have moved back to the Arctic for a spell now. A Californian academic commented on the radio this week that “What the British weather giveth it also taketh away”. Growers of oudoor crops are wondering what it ever gives them as we see a -3^oC frost forecast with pears and apples both coming into bloom.

Scottish growers had weather that was as warm as mid Summer last week but many centimetres of snow this week! Away from the most extreme winds of snow this weather is annoying for tunnel growers but not dangerous…. but what to do about doors?

Unless the location is very sheltered, Haygrove recommend Streamline doors for temporary and fixed tunnels where extreme earliness is required. Withstanding strong winds these doors and adding to the structural wind resistance of tunnels ends, Streamline doors provide 100% sealing.

Streamline door fitted to Solo tunnels

Most berry growers growing under 4-Series type tunnels on temporary sites opt for simple, low cost doors of the type shown in the image below. Makes sense…. cheap, quick to install etc.

Simple door, in open position (tied back to hoop)

….. But the climate is never right and every time the weather changes the grower must decide whether to spend money on labour, opening or closing OR lose yield or quality by compromising on the growing environment.

By far the best doors for field scale tunnels are ‘roller doors’. Unless the tunnels ends are staggered instead of straight of swept, roller doors can be set up to open several tunnels at once. Haygrove Farm now has many blocks kitted out with roller doors and for semi-permanent substrate fields the doors are now motorised. The new table tops have both doors and roller vents linked to climate sensors. Now we can concentrate on the plants and not the labour cost! 

Roller vents controlled by climate sensors

New raspberry pots with on line drippers installed

At the time of writing growers in England are recovering from the season and planning for 2012. We normally get enough rain for crops such as apples and cherries but 2011 was a very dry year.

Tree fruit growers are also planting at much higher densities (trees per acre or hectare) now – I do not hear of many new commercial apple plantings with in row tree spacings wider than 1.25m and most are 1m or less. These trees don’t have to grow much but they have to crop quickly and consistently from year to year in order to get payback within an acceptable number of years.

A dry year and a focus on early pay-back means that fertigation is much discussed right now.

 For tunnel grown crops, irrigation is an ESSENTIAL.

 For growers who have not previously needed to use irrigation this will be an important change and requires some learning.

For growers who have been using irrigation/fertigation on outdoor crops there may also be some important changes to make. One American pundit wrote that ‘Tunnels Change Everything’ and they do….mostly for the good…..but when it comes to fertiliser, tunnel grown plants are able to make more efficient use of key nutrients. There is less leaching of nitrogen and soil temperatures are higher. Reduced wind and UV light also promote the production of larger leaves.

Tomato growers tend to space the plants out a bit more, the same may rule apply to strawberries. However for tree crops, such as cherries, there may be other changes that can be made: More dwarfing root-stocks or perhaps even planting the trees even closer together!

Spring of 2nd year for cherries planted directly into tunnels

Why closer together? Planting close usually facilitates a more rapid year on year ‘yield build up’. Planting under tunnels provides a level of crop insurance so that the extra investment in trees is a safe one. Modern tree fruit growers know that closer planting actually makes vigour control and regular cropping easier. The trick is to manage the first months and years after planting so that the trees concentrate on fruit growing and not on timber production. Making sure that tunnel grown trees do that requires some thought and the management of irrigation should be the subject of a lot of that thought!