[al78]

A max-min thermometer placed in the greenhouse on the path between two raised beds claimed the maximum temperature reached 44.9C since early yesterday afternoon, and didn't drop below 21C, and that is with the door and roof vent open. I have a feeling it is overreading. There is no sign of stress on the plants in there.

[businessmonkey9]

I have tomatoes plated outside (crazy move I know) potatoes, onions and peas.

I only have netting (very fine mesh like but with tiny tiny holes), and straw. What would you guy recommend. To do.

[Mr Dog]

A max-min thermometer placed in the greenhouse on the path between two raised beds claimed the maximum temperature reached 44.9C since early yesterday afternoon, and didn't drop below 21C, and that is with the door and roof vent open. I have a feeling it is overreading. There is no sign of stress on the plants in there.

Day time air temperature should be measured in the shade, not direct sun. Overnight, there may be some residual (or generated if it's say wood chips) heat, although 21 does seem a bit on the high side. My max/min is badly placed (gets some direct sun during the day) and has regularly had readings above 40 recently. Also is it battery operated or mechanical? My old mechanical one used to occasionally get 'stuck' and give false readings.

[mumofstig]

I have tomatoes plated outside (crazy move I know) potatoes, onions and peas.

I only have netting (very fine mesh like but with tiny tiny holes), and straw. What would you guy recommend. To do.

Onions and peas should be ok with a frost, unless the temps dip very low.
Can you earth up the potatoes a bit more? That'll help them recover if the tips do get blackened.
I'd wrap the tomatoes in the straw and then cover with the mesh, but make sure you remove it in the morning, to let air get to the plants. Good luck!

[businessmonkey9]

Ok I shall leave the peas and onions.

Tomatoes I shall do as you have suggested.

 For potatoes. They have just come out the ground. Less then 5cm. Would it help to Earth up as much as possible, and cover overnight with a plant pot?

[Yorkie]

If they are covered with earth then the pot probably isn't necessary.

[JayG]

As long as the shoots are covered you shouldn't need anything else (obviously going to be variations round the country, but as a general rule any temperature of 4-5C or less can result in a ground frost on still nights - if the breeze continues it should prevent frost forming at those sort of temperatures except perhaps in the most frost-prone areas, which are typically sheltered and low-lying locations outside of towns and cities.)

[mumofstig]

If they are covered with earth then the pot probably isn't necessary.

I was going to say the same thing, but you both beat me to it 

[al78]

A max-min thermometer placed in the greenhouse on the path between two raised beds claimed the maximum temperature reached 44.9C since early yesterday afternoon, and didn't drop below 21C, and that is with the door and roof vent open. I have a feeling it is overreading. There is no sign of stress on the plants in there.

Day time air temperature should be measured in the shade, not direct sun. Overnight, there may be some residual (or generated if it's say wood chips) heat, although 21 does seem a bit on the high side. My max/min is badly placed (gets some direct sun during the day) and has regularly had readings above 40 recently. Also is it battery operated or mechanical? My old mechanical one used to occasionally get 'stuck' and give false readings.

That is why I put the thermometer on the path up against the north facing wall of one raised bed (which is 18 inches deep), to minimise overreading due to direct sunlight. When I checked yesterday the maximum was about 37C and minimum about 21C again. Is my greenhouse really elevevating the overnight temperature by eight or nine degrees celsius with the door and roof vent fully open? It might be the water barrels in there are absorbing so much heat in the warm sunny weather recently it is like having a radiator in there at night. This is desirable during the upcoming cold(er) spell, not so good in high summer-like conditions. I plan to remove the barrels when overnight minimums get back up to 7 or 8C, as the greenhouse interior is not cooling down as fast at night as I expected.

I am very interested to see what happens with the temperature in autumn and winter. Can I keep the greenhouse above freezing through the winter assuming an average or mild winter (obviously I'd have no chance with a winter month like December 2010)? If this is possible, would it be worth trying to grow Christmas ready new potatoes (with the aid of some bubble wrap and fleece)?

[mumofstig]

I suspect your thermometer is giving temperature readings that are too high.. In mine it hit 35C but dropped to 7C overnight. I can't see water barrels making that much difference to the overnight temperature - but what do I know 

I'd borrow (or buy a cheap) one for comparison - rather than carry on wondering 

[Grubbypaws]

What to do tonight? The temperature is set to fall to 0C but there is an 11mph wind gusting up to 30mph. I would have thought that the wind would mean it wasnt going to frost but the met office state 'Frost possible inland'.

I am not sure how I can safely secure fleece with the speed of the wind gusts 

What decisions have others here come to?

[al78]

I suspect your thermometer is giving temperature readings that are too high.. In mine it hit 35C but dropped to 7C overnight. I can't see water barrels making that much difference to the overnight temperature - but what do I know 

I'd borrow (or buy a cheap) one for comparison - rather than carry on wondering 

The thermometer did agree with my central heating thermostat, but it will depend on what temperature range the thermometer was calibrated. It may be the temperature inside my greenhouse was over the design range of the thermometer.

With a change of wind direction to a cool northerly and a lack of sun, greenhouse temperature max was a mere 24C with a minimum around 14C. I have closed the door and roof vent and covered the crops with a layer of fleece, so we shall see if that is enough to get them through the next three days.

[al78]

What to do tonight? The temperature is set to fall to 0C but there is an 11mph wind gusting up to 30mph. I would have thought that the wind would mean it wasnt going to frost but the met office state 'Frost possible inland'.

I am not sure how I can safely secure fleece with the speed of the wind gusts 

What decisions have others here come to?

If it were me and I had stuff outside which I knew wouldn't stand a frost, I'd put the fleece out and pin it down with plenty of ground pegs. If you haven't got ground pegs, some heavy bricks or paving slabs will do. Tents are just a thin canopy and decent quality ones can withstand storm force winds, so in the case of fleece, it is firrnly holding it down using weight or pegs which is the key.

Bear in mind the wind speeds quoted by the Met Office will likely refer to the standard anemometer height of 10 m, so fleece on the ground will be subject to  lower wind speeds.

If you cover with fleece and it blows away, the crops are no worse off than if you hadn't covered at all, the only loss is the monetary cost of the fleece. If you don't cover in fear of the wind and the crops get badly frosted, you'll never know whether it would have helped or not. It seems to me that given the worst cases in both situations, covering will give you the best chance of protecting your crops for only a small financial cost.

[Yorkie]

Bear in mind the wind speeds quoted by the Met Office will likely refer to the standard anemometer height of 10 m, so fleece on the ground will be subject to  lower wind speeds.

I never knew that! Every day's a school day 

[Grubbypaws]

Well it did frost here and the fleece stayed put weighed down with bricks.

It was difficult to get everything covered but I did. It looks as if we will continue to have frosts for the next 3 nights. Am I OK to leave the fleece on for that length of time or should I go to the effort of taking it off during the day?