Why is the heather so late?

[gavin]

This year the E Highlands heather is really late and the timing of my move of the association's bees to Glen Clova - on the old recommended date of the Glorious (I prefer to think Inglorious) Twelfth of August - was about right. I don't remember a year when that date was the best one with only the earliest tussocks of heather (we're talking ling, Calluna, rather than bell heather) out. Usually late July is the best time to take your bees to the hills.

Is it just temperature? In that case this map may help you see if the degree of lateness of your local heather makes sense. Mull, for example, may not have been as late as us if the state of the heather depends only on June and July temperature. See how wet it has been (again!) for us in the East during some key bee months.

Gavin

http://www.metoffice.gov.uk/climate/uk/2012/summer/meantemp_summer2012.gif
http://www.metoffice.gov.uk/climate/uk/2012/summer/rain_summer2012.gif

[Rosie]

I have always wondered what drives the heather to flower. On high or northern districts the winter starts earlier and that shortens the season, perhaps causing the heather to flower earlier than southern lowlands. On the other hand the days are longer (until the eqinox of course) in the North and the temperatures tend to be lower and that might cause the heather to be later. It seems though, according to Gavin's maps, the lower temperatures seem to delay flowering. This year everything else is late too. I wonder what will happen later on in the season. Perhaps late species will be in flower at the same time as earlier ones.

Steve

[Jon]

The willowherb is 3-4 weeks later than usual this year. There is still plenty about here and it should be long gone.

Interesting as well that my queens have mated well in weather which is twice as wet as average and significantly cooler.
The 7 frame nucs I made up with new queens at the start of July are getting overcrowded and I will either have to split again or transfer to full size brood boxes.
June was dire. Cool, wet and windy almost every day apart from a few days at the start of the month and given the lack of forage I had to feed several colonies a couple of kilos of fondant which I don't usually do. I had about 20 queens from the first batch fly and mate from apideas towards the end of the month and they must have flown is brief periods when the rain stopped.

[gavin]

Longer term (weeks) averages affect honey crop, short-term patterns (days) affect mating?

The triggers for flowering in plants are many and various. Some plants are controlled entirely by daylength, some by low or high temperature triggers, some by a time-temperature blend (day-degrees) possibly after one or a complex mix of triggers. With heather the plant has to grow for a while to make the stems to produce the flowers, then it probably 'decides' to go floral, then it has to actually get there by making flower buds and developing them. So warmth (day degrees) from a trigger of some kind is probably behind the precise flowering date each year. Maybe someone's researched it, I haven't looked.

Changes in the sequence of flowering of different plants (for example the spring trees) shows that they are using different cues.

Many plants have local types which are best adapted to the conditions locally. So these may require different triggers to go floral. It is entirely possible if you took cuttings of heather from Norway, Aberdeenshire, the Scottish Borders, Wales, Cornwall and Bordeaux (or even lowland heath heather and high mountain heather from the same region) and grew them in the same spot you'd find different flowering times.

[gavin]

Yup, the literature* says that Calluna varies, even to the extent of colder slopes in the hills having faster flowering (and maturing) variants than on equivalent warmer slopes. Varies geographically too.

Remarkably, heather is very responsive to elevated CO2, so that may be one contributor to the early flowering of heather in recent years. It flowers earlier and accumulates more biomass at elevated CO2 levels (+100ppm cf 1992 values increased biomass by 30%).

* In one of these papers, see this hopelessly optimistic comment published in 1992:

New Phytol. (1992), 122, 635-642
http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1992.tb00091.x/pdf

If worldwide CO2 emissions are stabilized at 1990
levels (as agreed by the European Commission for
Europe alone), 600 ppm will be reached at about
2600 (Watson et al, 1990).

- currently 393 ppm
- in 1992 about 353 ppm
- projections for 600 ppm now roughly 2070

[Kate Atchley]

Gavin, you start with "This year the E Highlands heather is really late ..."

The ling's late here in the West Highlands too though now it is coming into bloom it looks promising. Last year's heather was the best for years.

I sense the late flowering is due to cooler-than-average temperatures though we have had some warm spells, including this month's good temperatures. We've also had loads of sunshine enjoying the best Summer in the UK this year, it seems ... which more than compensates for the incessant rain of the Autumn/early Winter.

Could the heather's lateness also be due to the poor Autumn weather? Did that slow the plants progress down in some way?

No biologist me, as you gather!

Kate

[gavin]

Just updating this thread with the August maps. Available here:

http://www.metoffice.gov.uk/climate/uk/anomacts/

August was warmish in the west and wettish in the east. Once again, expect higher winter losses in the east for a variety of reasons including the health and vigour of colonies going into winter.

http://www.metoffice.gov.uk/climate/uk/anomacts/2012/8/2012_8_MeanTemp_Anomaly_1981-2010.gif
http://www.metoffice.gov.uk/climate/uk/anomacts/2012/8/2012_8_Rainfall_Anomaly_1981-2010.gif
On the other hand look at actuals rather than comparing to the long-term average and you see that things are different:

http://www.metoffice.gov.uk/climate/uk/anomacts/2012/8/2012_8_MeanTemp_Actual.gif
http://www.metoffice.gov.uk/climate/uk/anomacts/2012/8/2012_8_Rainfall_Actual.gif

If you want to take this further, take a look at both August ground and air frosts over the last run of years. 2012 had a widespread air frost as well as ground frost and it was that which put an early end to our heather season here.

G.

[Poly Hive]

If you base your move on the 12th there are years you will miss it totally. I can remember one honey show when I had some success with the heather class and the "worthies" were grumbling about no heather. I was up by the middle of July and took a very decent crop, they moved on the 12th.

PH