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I can only find one - VERY expensive - a Hortipower PG200N.

Use a cheap luxmeter and the simple conversion as above - perfectly close enough. If you hunt online, you will find that different CCT lamps vary by not much in that figure of 17.

At the end of the day a mole (mol) is just a number, so can be applied to anything, albeit most would make absolutely no sense at all - a football crowd of 0.00000000001 mol? (I did not count or calculate the zeros    ).

Amaryllidacae?

(A guess at spelling.....)

Going deeper, probably non-hardy species of.

Sorry - re-read and you ask for genus. In that case, probably not even a bulb?

A very great deal of what appears on the www about lighting for plants is nonsense - I have not read anything on your links so far, so cannot comment.

I used to work in lighting/lamp R&D and have trawled lots of the literature produced by Philips about commercial horticultural lighting, and I have written an article for the SABG newsletter that will appear in early 2024.

One simple fact - growing rooms use around 600W of LED lighting per sqaure metre. All of the articles that I have found online suggest far, far, far lower levels of illumination.
The only way to provide really useful levels of light for growth is to use commercial horticultural lighting - it is impossible to cram in enough lighting designed for domestic use.
Flowering is usually triggered by photo-period and that can be at very, very low levels.

Another important point is that the human eye is of no use in judging light levels - it is an amazing bit of engineering and compensates. Most people can read, just, at around 100 lux, whereas a bright summer's day can be around, or even over 100,000 lux, even in the UK. Try one of these if interested -

https://www.amazon.co.uk/dp/B07QFXSDKL?psc=1&ref=ppx_yo2ov_dt_b_product_details

One thing that did surprise me is that amounts of light are now routinely quoted in moles (mols) within horticulture. I was briefly asked to look at developing a metal halide lamp specifically for promoting photosynthesis and we used plant growth lumens at that time (very different to human eye photopic lumens, which is what lamps for domestic use are quoted in).
Conversion from human eye photopic lumens depends on colour temperature (essentially balance of red and blue content), but a serviceable conversion is 1000 lumens of white light (any CCT) is ROUGHLY 17 µmols of potosynthetically active light/radiation per second.

Some useful links -

https://engaging-data.com/solar-intensity/

https://en.wikipedia.org/wiki/Photosynthetically_active_radiation

https://www.lighting.philips.com/application-areas/specialist-applications/horticulture

https://www.assets.signify.com/is/content/Signify/Assets/philips-lighting/global/20230124-philips-gridlighting-technical-specification-sheet.pdf

https://www.assets.signify.com/is/content/Signify/Assets/philips-lighting/global/20230124-gridlighting-photosynthetic-flux-density.pdf

https://www.lighting.philips.co.uk/application-areas/specialist-applications/horticulture/greenpower-specialist-applications/led-flowering-lamp

Very few people in the UK grow them and rather few species offset at all or those that do, generally do so only very slowly, so any "spare" bulbs would normally be seed-grown. Seed is ephemeral and in most species is produced during late summer

Even in RSA, both bulbs and seed are scarce in trade and not cheap.

Imported bulbs have been available from Amand via UK EPay at around £50 each, although I do not recall the species that he was offering, although there were at least two. Being imports, they would have been 6 months out of sync' with the UK.

Posted elsewhere here, but should you not have seen it, free download - issue 36, spring 2023 - https://www.cactusandsucculentreview.org.uk/

The calorie that everyone talks of is actually the kcal.

As for kWhr - it produces a "reasonable number" for most uses. Who wants to be routinely talking about energy use in units of 10^6 joules?

It happens all over the place - pick something that produces convenient numbers to remember, what anyone calls it is irrelevant for 99% of the time.

Another hobby of mine is hifi. Tonearms (on record-players) have what is known as effective mass and this varies in the region 5-30 grammes (roughly speaking).
It isn't a mass, so the units are not g, and the convention is to ignore the decimal place.
It is actually inertia, so the units are mass multiplied by distance squared. The real position of the decimal point is ignored to get that simple figure of a one or two digit number around 10-20. Everyone does it, very, very few people know what it really means, but the system works. (The inertia (effective mass) of the tonearm interplays with the compliance of the cartridge suspension, so is important).

The symbol for hertz is Hz 

Quote from: Martin Bohnet on December 23, 2023, 02:52:19 AMWell, actually all mechanical technicians and engineers i know and work with think in milimeters, anyway, and do not flinch at all when going down to µm.

I do not doubt that for half a moment (imperial measurement, I believe), but another red herring.
When I worked in the plastic films/coatings industry, pretty much everything in terms of thickness was measured in microns, or fractions thereof. Only roll lengths and widths did not - m and mm respectively.

Horses for courses. As I said, a vanishingly small percentage of people in the UK have the first clue what the Kelvin scale or 1K is.

The unit(s) is/are Kelvin, there is no plural - 1 Kelvin, 50 Kelvin. The Kelvin scale also adopted the convention that both K and C scales used the same scale, in that a 1K interval was a 1C interval, so the K scale "stole" the interval size/scale from C.

Quote from: David Pilling on December 23, 2023, 04:50:52 AM5-bob on them dropping the blokes' names from units and just going with letters at some point?

Most people that I have worked with have used K rather than Kelvin - the CCT is 2700K is said as twenty-seven hundred kay.
Who uses anything but C and F? Very, very seldom does anyone hear centigrade (or celcius) or fahrenheit.

My background, ecucation and career are all science. I have no problem working with any units in the imperial or metric systems and can generally convert between most of the "equivalent ones", in my head to a close enough approximation.

The first and only time that I have ever known anyone outside of science use Kelvin was 7 posts above this. To be honest, I don't recall anyone using Kelvin outside of academia, although it must have happened - even when I worked with industrial ventilation systems, I was almost certainly the only person that knew why 273 was added to C gas temperatures to achieve mass balances.
In the UK, only a small % of people will know anything about Kelvin, even the people who quote them as the CCT for lamps will generally have not the very first clue. It is, after all, a totally unneccessary complication.

In many everyday uses, imperial units are far more flexible/useful.
I use imperial when wood working for instance - 12 inches - divide it by almost any number and accurately mark out a length of timber. Halve it, halve it again, and again and again, now mark that accurately. All quite easy
Do the same with 30cm.

If measuring something, I remember whatever is easiest - the nearest to a whole number - I would remember 1 foot rather than 30.5cm (actually 30.48cm, but no quick and simple measurement device can measure that accurately.)

Quote from: Martin Bohnet on December 22, 2023, 08:40:12 AMThat's not a mix.

Maybe not in Germany, but elsewhere it absolutely certainly is.

1°C may be 1K (as in divisions, not actual temperature) but most people would not have a clue (about the Kelvin scale) and certainly not mix the two.

Hence my comment

Quote from: Martin Bohnet on December 21, 2023, 11:53:24 PMColleagues at work dread cold times because my mood will drop with every Kelvin below -5°C at night and every day with an average below 0°C.

I really like the mix of units/scales there Martin   

Quote from: David Pilling on December 18, 2023, 03:46:32 AMit is taxed at a lower rate in the UK and is legally only permitted to be used for limited purposes. It still exists in 2023 although where it is allowed to be used has just become more limited.

Another name was agricultural/tractor diesel, or gas oil (which is what it actually is), but it was also permitted for use in stationary and boat engines. It isn't actually dyed diesel, but it is dyed, and close enough for most, but not all, applications that it can be used instead of white (fully tax-paid) diesel.

I was "assured" that it would very shortly disappear something like 5 years ago, by someone who owned a canal barge, which travel something like 4-5 miles per gallon. He implied that it was an end to all red diesel.

Looking at current law, it seems that the legal users are very largely still legal, although boat engines are restricted to marine (which is presumably correct, as in salt water only), and commercial space heating isn't allowed either.
Around here, the canal marinas were THE source for hooky diesel for vans.

Quote from: David Pilling on December 17, 2023, 04:30:16 PMOn weather stations I beg to differ. The link I gave goes to a map that can be zoomed to street level and the weather station belongs to a neighbour I know,

That maybe the case with you.
I could see nothing but the same points close to me as used by the Met' Office.

I am unsure if the Met' Office actually maintain very many weather stations themselves - two near here are airports, one of them military.

The diesel figure was never going to be correct at 2p/kWhr.

Presumably central heating oil has escaped the application of VAT that now applies to red diesel (presumably, red diesel no longer exists)? If so, central heating oil will probably now be the prefferred choice of van drivers who won't pay for fuel at "full" price?

I just buy vehicle fuel - I need it, so buy it, so have no idea what they are in the UK now, except that petrol contains several % ethanol.
I wonder where all the spent oil from commercial premises went before conversion to diesel substitute was an option?

As a point of interest, which surprised me when I did some digging after someone asked, to make vegetable oils compatible with diesel engines, it has to be partially hydrolised, which generates glycerol as a by-product. (All natural fats are tri-glycerides - three fatty acids attached to one glycerol molecule).

I have no idea what is done to vegetable oils to make it burn like Jet A1, quite possibly the same thing?

Quote from: David Pilling on December 17, 2023, 04:00:28 AMWeather Underground is a useful source of more local weather data

I have not searched in detail, but the locations look to be the same as the Met' Office use. If you use the Met' Office website, you put in your postcode and a list of local weather stations appears on a drop-down menu  and you choose which one you want, which appears to be the same.

Quote from: David Pilling on December 17, 2023, 04:00:28 AMBubble wrap seems popular in the UK for lining greenhouses in the Winter. The temperatures are probably around the sweet spot for it.

I am unsure how there can be a "sweet spot" for insulation of a greenhouse when bubble-wrap costs peanuts, assuming that you don't throw it away every year, or is free. I suspect that insulating the bench cost around £4-5, I have not worked things out in detail.
I only have to save something like 15kWhr and I am ahead. I am sure that there will be U values for bubble-wrap online somewhere, but life is far too short.
The heat lost from the insulated bench, into the bulk of the greenhouse - 8 x 12 - raised the greenhouse temperature by about a degree, assuming all that heat came from the insulated bench, ignoring any contribution from the concrete floor etc.

Quote from: David Pilling on December 17, 2023, 04:00:28 AMthe determined reckon on £0.02 for a diesel fuelled heater off ebay.

Diesel, on full combustion, liberates around 44MJ/kg.
One kWhr is 3.6 MJ.

So 1kg diesel when burnt liberates a little over 12 kWhr of energy. Diesel is close to a density of 1, so, near enough, 1kg is 1 litre. A litre of disel is around £1.45, so IF all the energy could be used, heating using diesel would cost around 12p per kWhr - more expensive than domestic mains gas.
However, two problems - you need ventilation (an oxygen supply) for combustion, you do not for electric heating, and ventilation means lost heat, also the combustion products must be disposed of, which also means lost heat.

Modern household boilers burning gas, all singing, all dancing, can get around 90% efficiency. (Even old gas boilers achieve over 80% efficiency. Which is why the economics of changing an old for a new boiler, so long as the old one works, do not stack up. It will depend on fuel prices, but generally, the payback period for the new boiler is longer than the expected life of the new boiler.)

Diesel is pretty close, chemically/in terms of combustion, to central heating fuel. I have never heard anyone suggest that oil central heating was a fantastically cheap option in the UK.

Just by way of information..............

My collection was started again a couple of years ago, so is not huge - overspilling a 12 x 3 bench now, but I was determined not to heat the entire greenhouse, as mentioned in the thread referred to.

I have rehashed everything properly (last minute, only a week or two ahead of frosts).

The greenhouse long axis is north-south, so the great majority of light comes in via the south end and roof.
I have double bubble-wrapped the west- and north-facing walls from just below bench level to the eaves, and single bubble-wrapped the south end (my greenhouses sit on one course of concrete walling blocks, so are an extra 10 inches (?) taller). The east side of the bench is the path within the greenhouse.
At eave level, I have secured some 3 foot wide wire netting, as a "roof" over the bench, supported on some 8mm studding and small battens (lengths of broom handle).
I have stretched single lengths of stout wire at eaves level, againt the wall, and along the front of the wire netting.
A length of bubble-wrap hangs on the front wire, like a curtain.

When the forecast is for under 5C, I "draw the curtain", and lay a length or more of bubble-wrap on the wire netting. It isn't "air-tight", but everything overlaps so there are no huge leaks.

I bought a couple of plug-in energy "meters", and the 12 x 3 x 2.5 foot cloche used 4.5kWhr of electricity to maintain 6C difference to ambient over a period of 15 hours (5C in the cloche, average -1C outdoors (from local Met Office weather station data and probably a little cooler here, maybe an extra degree, as I am outside of town)). So, around 0.3kWhr per hour. Two consecutive nights were very similar, both in average temp. and in energy usage - I was very pleased, and amazed.

I could not find what I thought was near enough to an ideal (fan) heater, so made some. The cloche has 2, running at 250W, but switchable to 500W if the weather gets very cold. The fans run so long as the greenhouse temperature is below 6C, in other words, always circulating when the weather is cold. The fans run at ~20W.

Page 4, towards the top of the RH column -

"There have been no reports of it becoming problematic in the wild"

Quote from: Robert_Parks on December 10, 2023, 07:38:24 AMPresumably G. tinctoria is already banned?

Yes, banned a few years ago, hence my comment about worst case parent.

If you look at the "logic" of the whole thing, it is being banned because it is a hybrid of a banned species, no other reason. Maybe somewhere down in SW England, or somewhere very close to the coast in the W of Scotland (which actually has a very mild climate over large parts due to it getting "hit" by the Gulf Stream), there are large stands of the plant outside of gardens and parks, "feral"?

I have lived in S Devon and W Scotland, and saw no evidence of any problems.