PBS Forum

Quote from: Arnold on January 06, 2024, 12:20:35 PMUli

Paint the water bottles black and you'll do much better with stored heat.

Possibly, possibly not as the water cannot get hotter than the greenhouse, but the loss rate when the temperature falls will certainly be faster to some degree.

What is a better absorber is, by equal measure, a better emitter.

Quote from: illahe on January 05, 2024, 09:29:21 PMI think 5' would be ideal here as well, but high groundwater where I'm at makes that an impossibility,

One of the limitations to ground source heat pumps is ground water/soil moisture - they are better conductors of heat than dry soil.

I forget which one, but at least one very large country house in the UK uses their large lake as their heat source. If nothing else it is a hell of a lot easier to locate the exchange array compared to digging miles of trench.

Many thanks @Carlos 

Thanks Mark @illahe

Yes broadly similar, your foliage looks slightly lusher, which is probably down to numerous reasons of culture here v. with you, but it also means that the infected leaves here are generally drier throughout, from the first hint of a problem to the whole leaf suffering.

I have sprayed the affected plants a couple of time with systemic fungicide, but suspect that it is too late to produce much/obvious of an effect this growing season.

I have changed things around this winter and suspect that they were around two degrees warmer, as a minimum, last winter, so maybe the clue is that. But we have had/are having the mother of all wet winters so far too; irrespective of any leak, ambient humidity must have been through the roof for long periods.

The greenhouse leaks a bit here, fortunatley, just in the corners, so RH is definitely too high this autumn/winter - it has barely stopped raining for weeks upon end here.

It just struck me as odd that two Ferraria had shown what I am sure is rust.

I did buy some systemic fungicide a week or so back........

The plants are kept at 5C minimum and I was surprised to see what must surely be scorch (too low a temp.) on Pauridia capensis - the leaf tip blackend to 3-4mm. 

One batch of over-wintering Haemanthus humilis seedlings also have very dark leaves, which looks like cold-damage, although the leaves are still firm, and the 2-3-4 other clones, all larger, look perfectly OK.

(Now considered to be Colchicum.)

I have sown several species, from 2-3 suppliers, over the past 18 months or so, sown late summer-early autumn to cycle cool to warm, in the greenhouse. Having a very minor sort of the greenhouse, I now realise that nothing has germinated, so far.

I am now collecting the several pots to try some experiments in a heated propagator.

Does anyone have any experience from seed?

I suspect that they aren't very popular, but I like several species and ssp.. I don't believe that I have ever seen bulbs for sale anywhere, or as part of society bulb X, so it must be at least uncommon.

My question was really if rust or anything similar is common on any Ferraria.

So far as I recall, the only time that I have ever seen rust before has been on wild grasses; I don't think that i have ever seen it even on roses. And yet two plants near certainly have it this winter.

Ferraria are part of the iridaceae and most iridaceae seeds germinate a lot more freely when sown very fresh - as soon after they are ripe in the seed pods as possible.
Once they dry completely, many are slow to germinate and many species will germinate erratically over years, even several years, if they germinate at all.
I have sown Ferraria only a few times, different species, and germination has been erratic, although some batches of seed have produced good numbers of seedlings very fast. 3 weeks is no time at all. Be patient.

I doubt that any Ferraria species regularly sees temperatures below 5C, so personally, I would not subject seed to that low a temperature. Temperature changes (night to day change of 10-15C) probably stimulate germination.

Quote from: OrchardB on December 31, 2023, 02:37:04 AMHeat stores/recovery systems, in boxes, or snaking through the garden, are still being promoted of course.

They are called air-source and ground-source heat pumps.

Air-source start to struggle as temperatures drop. Ground-source heat-exchange piping is usually installed at a depth of around 1.5m (5 feet) - it needs to be that deep to remain at a reasonably constant temperature when in use (in the UK - 10C)

I do not see how these PCM tiles can work as they give up all their energy at one temperature as the temperature is reached - it will not be absolutely precise but once a temperature is reached the change happens and the heat is given out.

What happens as the temperature rises slightly? Presumably the panels chill the air as they change back? Which is not what you want at all.

They don't seem to provide anything like enough joules either.

I accurately measured what it took to keep the large cloche that I am using, inside my greenhouse, an average of 6C above outdoor temperature, over-night (15 hours). The cloche is made from bubble-wrap, two layers to the outside wall of the greenhouse, around 3 cubic metres/cubic yards - near enough the same for this exercise. That was around 4.5kWhr, which is around 16MJ - 16000kJ

When I was heating the entire 12 x 8 greenhouse, I needed a bare minimum of 1kW of heating to cover most frosty nights. In reality, there was far better distribution of warmth and a good margin for extremes, by using two 1kW fan heaters, one at each end of the greenhouse, controlled by a solid state thermostat with a bare sensor. From memory, 1kW would give a temperature difference of around 8? 10?C outdoors v. within the greenhouse when running all the time. That is 3600kJ/hr.
The greenhouse was completely lined with bubble-wrap.

I wish I knew where it is, but Kew did lots of measurements over several years across various sites and published figures to calculate how much heat any greenhouse, anywhere in the UK, would use if kept at temperature X. This was back in the 1960's? 1970's?

There are calculators online, but compared to the Kew one they must be pretty crude - the Kew one required figures for floor area, glass area, location (as in where in the UK, so allowing for local climate and day length), and minimum temperature required. It also allowed a figure for leaks. 
It was compiled before anyone seriously bothered with insulation but the number would still be close enough.

I have grown pedio- and sclerocactus from seed too, and used the same "technique" - outside all winter.

I am unsure how similar the growing conditions are but La Mancha and Iran may be a lot closer to each other in that respect than to Saffron Walden in the UK (which, long ago, was at the centre of a thriving saffron "industry", hence the name.)

Very dry all year, heavy alkaline soils would be where to start - S.W. is in East Anglia - my home area and it is not a desert only by virtue of the fact that the meagre rainfall is evenly spread over the entire year. Historically, huge tracts were used for sheep grazing as the land was fit for not much else - numerous towns and what are now villages made fortunes from the wool industry.

Lots of information should be online, but I used to live near Long Melford - a large village today - which has an enormous church, fit to be declared a small cathedral, and lots of other features, all paid for by the medieval wool trade.

When I was sowing large numbers of seeds, more than numerous species of hardy plants, they were always put out on what amounts to a trestle table, outside in early autumn, open to the elements.
They always got at least several fosts each winter, generally down to -3C or maybe a little lower. Some winters there was a freeze of a few days, others not.

It seemed to work OK.

The only particular seed that I remember failing with, treated like this is two species of giant Lobelia, 2 years ago. There will obviously have been others, but not quite so potentially spectacular and failures weren't that common.

Other seeds - pretty much all pot in a bag, although I sowed some Othonna yesterday and, like geophytic Pelargoniums, they require cool temperatures to germinate - they are in the unheated part of the greenhouse until frost is imminent, when they will be moved.

Quote from: David Pilling on December 29, 2023, 03:41:30 AMmy conclusion sticking things in the fridge was never as effective as real Winter (putting them outside)

It (the fridge, or freezer) doesn't really replicate any natural process and given that we don't really understand how germination is delayed in any detail, I would agree.
Even at the simplest level temperature isn't varying and if something needs to be washed from the seed, a fridge is not replicating rain.