Friday, 15 March 2013

A Convincing Argument Or Not?

No improvement in the weather today. It wasn't too bad in the morning but we had a few spots of rain in the afternoon just enough to register 0.2mm on my rain gauge. The morning was once again frosty and it didn't warm up much through the day.

I’m still trying to decide whether or not to sow some seeds. If the sun’s out it’s quite pleasant in the greenhouse but the last four nights have seen below freezing temperatures in there which is not conducive to seed germination. I decided to look at some of the temperature statistics over the last four weeks to help resolve, one way or another, my seed sowing dilemma.

I was looking through this blog which suggest some suitable soil temperatures for seed germination. Without going into detail the suggestions are that somewhere between 7°C and 10°C should be suitable where 7°C is really an absolute minimum. The chart below plots our outdoor temperatures over the last four weeks. 

Over the last four weeks we have had occasions where the outside temperature has exceed that minimum value of 7°C but the temperatures haven’t exceeded 10°C in the whole of the four weeks. The last time we touched the dizzy heights of 10°C was on 04 February 2013 and the ‘heat wave’ lasted for less than one hour. I’m convinced that for us sowing anything outside at the moment would be a waste of time and money.

That leaves sowing in the greenhouse. Assuming the same sort of germination temperatures are required then the hours above 7°C are shown below.
Clearly in the greenhouse there are a lot more hours above 7°C. I've actually chosen 7°C as one of my greenhouse critical temperatures and keep a check of just how many hours are above that temperature. I updated the database figures on 13 March 2013 and the result was that 73 hours out of 312 hours in total were above the magical 7°C level. On the negative side we've had 29 hours of below freezing temperatures in the greenhouse in March. To put that into perspective there were just 3 hours below freezing in March 2012 and only 33 hours below freezing in the whole of February this year. I wouldn't expect seeds to germinate in the greenhouse in February.

Until the weather warms up I've decided not to sow any seeds outside. In the greenhouse the options aren't quite as clear cut but I still think it would be wise to curb my enthusiasm and hold back a little longer before getting down to sowing any of this year’s crops.

To finish off with and on a much brighter note here’s a picture of a siskin I managed to photograph in a break from number crunching.

Copyright: Original post from A Gardener's Weather Diary author M Garrett


  1. A lovely photo. I've never seen a siskin.

    1. They never stay for very long. Just eat a few sunflower hearts and they're off.


Thank you for visiting my blog and leaving a comment - it is great to know that there are people out there actually reading what I write! Come back soon.
(By the way any comments just to promote a commercial site, or any comments not directly linked to the theme of my blog, will be deleted as soon as I spot them) Please do not follow links from any comments that appear to be spam - if in doubt ignore.