PBS Forum

Hmmmm

The usual density of LEDs used in horticulture for growth, without any natural light, is 600-700W/sq. m, so yes, that will get hot if you are anywhere near that (they may be far more efficient than incandescent lamps, but well over 99% of the energy is emitted as heat).

A lot of people think of S African plants, especially succulents and bulbs, as universally growing in very dry habitats. That isn't so, very many do grow in seasonally dry, or even very arid areas, but it is seasonal and many have copius amounts of water during their growing season - quite a few species, even some Lachenalia, for instance, naturally grow in shallow standing water -a handful of species even have the specific name "aquatica" as a consequence.

As a guess, plants such as cono's are "designed" to lose rather little water while in growth. Bulbs may have fleshy leaves, but they require quite a bit of water when in growth in pots and, unfortunately, it is perfectly possible to have moist air above very dry compost.

Maybe the "simplest" thing to try is to separate the air flow so that most (almost all) cools the LEDs without getting near the plants, and then try growing the bulbs without covering them?

When I grew many hundreds of cacti and succulents, I would sterilise everything for sowing seeds and did perfectly well. For bulbs I now assume that the commercial compost is "sterile" as is claimed (in reality it has been sterilised, but the bags have tiny holes so that they can be stacked for transport, so aren't actually sterile, but will be free from seeds).

With Strumaria and any amaryllid seed that arrives pre-germinated, I use either a cocktail stick or piece of stainless steel wire and make a hole deeper than the length of the  root that has formed and use tweezers to "plant" each seed with the actual seed sitting in the top of the hole. The bulbs always form under the seed, so they form below the top of the compost. I would not use any grit as a top layer for sowing, unless it is tiny - 2-3mm.

Based on you photo' I would suggest that you add 2-3-4mm of seived loam to the top of the compost mix in your pots -it will settle a little when watered/misted (I use a hand spray to water as it is more accurate and far more difficult to over-water). That loam should help the seedling anchor itself better

Mould that is visible is undoubtedly due to high RH. I am unsure why the temperature on a windowsill would go over 30C during the day though.

RSA has a minimum (winter) daylength in Cape Town of around 10 hours, and obviously it is longer as you travel north in RSA. As for your seedlings, they look essentially normal, apart from the yellowing, so light level must be at least close to being OK.

Growing SA winter-growers where you are is not going to be easy without considerable hassle and expense, unfortunately.

That is very warm compared to here - daytime temperature is whatever the weather provides although the minimum temperature will only ever be around 5-6C at any time of day or night.

Provided that there is good drainage, seedlings can be watered reasonably freely. That said, I would never use extremely high mineral compost - something like 50:50 coarse gritty sand:conventional potting compost - in my case John Innes (loam-based). If the picture shows your compost rather than a top-dressing (which I do not use for seed/seedlings), it seems almost devoid of any water-retaining component.

In my experience, seedlings only die-back in response to decreased and then no watering, so they will be green until March-April.

The 3-4-5 species that I have grown from seed have been easy to raise. Unless home-produced, the difficult bit is getting seed before it dies as all that I have known germinates in the seed capsule long before the capsule dries.

If the red item on the surface is a bulb, it should be 5-10(+)mm below the surface, in which case this implies your compost is wrong.

Hybrid vigor is not guaranteed in anything, sometimes it happens, sometimes not. If you trawl the literature poor performance in hybrids is mentioned frequently - if all showed vigor, the plant breeding industry probably wouldn't exist as it does.

Zubov appears to be at least a semi-professional botanist, he called it candidissimum 3 years ago.He has lots of mentions in Kew publications.
The plant gets a few mentions across the www as the species.

If that isn't good enough and it gets no mention in the latest monograph, I would suggest that you are very unlikely to get any better informed short of contacting Grey-Wilson (et al). He is or was here -  kit@agsbull.demon.co.uk, if that does not find him, he will be contactable via the AGS.

Your council of perfection may be the enemy of the good - the plant seems reasonably well distributed in cultivation as C. candidissimum.....

Quote from: David Pilling on January 07, 2024, 04:13:23 AMWe've all heard of the 'greenhouse effect' - radiation goes in, but can't at a different wavelength get out. That's why it is so hot.

I very strongly suspect that that is very largely or entirely urban myth in terms of why greenhouses get hot/warm.
The last (scientific) consideration that I read was as I mention above. Otherwise, that was my belief/explanation until I read the article.

Lots of common liquid fuels are going to have very very similar heats of combustion - they are all various mixtures of hydrocarbons at the end of the day. The one uncommon one being alcohol, which is not a hydrocarbon. Where they differ markedly are in vapour pressure and flash point.

If you are adding heat, no matter how modest the source, the temperature cannot help but be raised, it is just a question of how much. Lots or people used to use a 60W or 100W indandescent lamp for frost protection and/or to discourage condensation, in unheated buildings, such as garages. As kids, my father grew a LOT of potatoes, and the store for winter was a large wooden trunk, wrapped with layers of old carpet and hessian sacks, in a very small wooden shed that had a suspended floor. When frost threatened, he used to burn a small hurricane lamp in the shed. Every once in a while, they were taken out to check for any rotten ones, and although it must have happened, I do not recall any frost-damaged ones, so it wasn't common - in Colchester, so in one of the winter-chillier parts of England, short of heading for the hills.

As for the temperature "inversion" day-night in a greenhouse, quite possibly an effect of heat being given off by the floor at night. If so, the effect should change quite a bit between either end of a series of several days and more, of low temperatures day and night (which we/I are/am headed for this coming week - "normal" winter temperatures - nothing above 5C and plenty of time around 0C or slightly under). If the greenhouse doesn't warm appreciably during the day, the floor may even be an overall heat-sink at night (concrete has a SHC around 1 and earth/soil a little less).

If anyone wanted to make best use of the bottled water idea, they'd be near the glass while there was any sun, and in the middle of the greenhouse otherwise. Leaving them near the glass just ensures that "some" of the heat is lost to no effect.

I did once view a house - 35ish years ago - where the owners and their son were tinkerers with modern technology - they had a small wind turbine and a solar panel. The solar panel was not generating electricity - it was a long way before that idea was developed significantly - the panel was a serpentine wound clear plastic pipe sandwiched between glass and black-painted (probably) plywood and it stored energy as heat in a very large underground water tank. It was a long while ago, but the panel wasn't small - 6-8 feet square, maybe more.

Latent heat of change of state is usually huge, far in excess of SHC, which is why regrigeration and related plants, and much else, uses change of state rather than simple change of temperature. (One of the great whte hopes that is being persued for storage of solar energy is common salt - using the molten state, stored underground.)

Quote from: Uli on January 07, 2024, 02:20:13 AMVery good idea, indeed. Thank you! I will paint some at first and compare. Not sure if it is right that the water cannot become warmer than the air in the greenhouse. Radiation behind a glass pane is very powerful. Black pots and aluminum become very hot

Radiation behind glass is the same as on the outside of the glass, unless you have some unusual glass. (Actually, it is quite a bit less as the glass absorbs far more than you imagine or can perceive with the eye.)

The reason that a greenhouse gets warm/hot is that there is no change of air, or not much compared to outside, even in still weather, not least, unless you have an entire roof that opens, there is no convection (rising of warm air).

The SHC of water is 4.2kJ/litre/degree C.
Assuming that the water gets 20C above what you require as a minimum, that would be a contribution of 84kJ/litre, although you culd never get all of it emitted as the loss rate from the water decreases as the temperature drops.
One kWhr is 3600kJ, so you would need all the heat from 43 litres of water warmed by 20C to store 1kWhr of heat. It will also lose this heat as the greenhouse cools rather than when it reaches your minimum temperature.

The water is having essentially no effect, although where you are located it probably doesn't matter much, if at all.

There are a handful of photo's online but the best is the SRGC website, reply 5, and on, source/habitat being given as Azerbaijan. The contributor gets vast numbers of mentions online.

Photos of Spring flowering Colchicum from D. Zubov (srgc.org.uk)

Colchicum candidissimum #floweringtoday #thebulbyard #colchicum #bulbs #twitter | Plants, Crocus, Meadow (pinterest.com)

Colchicum candidissimum 20180208 0002: Colchicum candidissimum 20180208 0002 (edgewoodgardens.net)

https://www.pacificbulbsociety.org/pbswiki/index.php/DimitriZubov

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.