South African Bulbs/Geophytes 2018

[PaulFlowers]

Arnold

My set up is in a very bright (when its sunny) south facing conservatory. That part of the house is cold in winter but always above freezing .

I built a 1M square unit out of plastic pipes to support the lighting unit, which hangs down from it using adjustable cables. The lights, and their fans, do generate heat and raise the day time temperature considerably if it is a sunny day but as the lights are on a timer, the temperature dips down cold at night. 

The LED unit was very expensive and has two switches 'grow' and 'bloom' - I don't really understand the mechanism, or if it had to do with the switch to bloom setting, but most of the bulbs flowered much earlier than they should, so the lachenalia, gladioli, moraeas were all flowering in January. Then again, we had some very cold nights in July and many of the bulbs started much earlier than they should have this year too. Equally, I bought some tulbaghias a few weeks ago, and as it was too cold for them outside, they were under the lights and are all blooming now.

Hope this is helpful - I can send you specs and brand of the LED lights if you'd like

All the best
Paul

[Robert]

Moraea elegans is looking good now.

[ArnoldT]

Paul:
Thanks for the details.

I've read much on LED's and Kelvin Temperature and wave length.


I have to say I'm a bit confused.

Each manufacture has their won set of numbers and figures.


Looks to me like the market drivers aren't  those of us that grow flowers for their beauty but those that grow their plants  for other reasons.

[Steve Garvie]

It is all fairly confusing Arnold.
Until recently the main driving force behind the development of LED plant lighting has been Cannabis growers on the one hand and the aquarium/vivarium hobby on the other with hydroponics growers and professional horticulturists also now joining the party. Each tackles the issue from a different perspective.

Green plants look green because they preferentially absorb light of certain wavelengths and reflect what they don’t use. Photosynthesis is mainly driven by absorption of light between 400 and 700nm -this range is referred to as PAR (Photosynthetically active radiation). Within this range there are absorption peaks at both the blue end (400-480nm) and the red end (650-700nm). The area in between is mainly green-yellow light; the human eye is most sensitive to light in the 550-650nm range.

If you were to design an efficient artificial light to preferentially grow plants this lamp would emit blue light peaking at about 430nm and red light peaking at about 720nm. LEDs tend to emit light of fairly narrow wavelengths -the specific wavelength dependent upon how the LED is constructed. So by carefully choosing your types of individual LED it is possible to create a group of LEDs which selectively output light at the plants’ desired wavelengths with almost all the energy input being directed into plant-useable light. Such a multi-LED lamp looks peculiar to the human eye and does not appear to be particularly bright.

If you are displaying plants in an aquarium or vivarium then aesthetic appearance is paramount. White light is required to give it a natural look. There is however no such thing as pure white light as white light is composed of varying amounts of red/yellow/green/blue/violet light. The exact proportions of each dictate how the white light is perceived by the human eye. More red/yellow-green produces a “warm” white light whilst “natural daylight” has more blue and is described as a colder light. These “thermal” terms have no scientific meaning as white light is also often labelled by its colour temperature measured in Kelvin -paradoxically the higher the Kelvin temperature the “colder” the appearance of the light! Warm white light is usually around 3,500K whilst Natural Daylight is about 6,500K.

In a planted vivarium the plants will look their most natural (to the human eye) with a white light of about 6,500K. This light will have blue and red components (as well as all the other colours). If this light source is very strong (bright) then it will contain enough red and blue light to drive effective photosynthesis BUT it has a low bang for the buck as only a modest proportion of this light’s energy consumption goes towards producing “plant-growing light”.

If you simply want to grow plants under artificial light and keep power consumption to a minimum then a selective PAR light source is required. Paul appears to be using a Platinum light unit which has selective LEDs producing “blue-heavy” and “red-heavy” light (I think they also include near infra-red and UVA LEDs also) -this unit will produce great plant growth over its intended coverage but will look alien and bizarre to the human eye. It does however produce great plant-growing light for the energy consumed. There is evidence that at least in certain plants (most evidence comes from cannabis growers), green leaf growth is most dependent upon blue light whilst flowering is induced by increasing red light exposure which is why many units (including the Platinum unit) have a “growth” button and a “flowering button” (the latter switches on more red LEDs).

The science is more complicated than I have described above and I perhaps should include a disclaimer that I do not and never have cultivated or used cannabis! 

[Robert]

An interesting discussion of LED grow lights.

I have to admit that I do not use and know nothing about LED grow lights, however a few things did come to my mind. Visible light runs in the 10¹⁴ Hz to 10¹⁵ Hz range. When considering waves, not only does wavelength/frequency need to be considered but also amplitude (Power, i.e.Watts). Light emitting diodes are known for their low power usage (Wattage). I do not know, but maybe this affects photosynthesis for the plants growing under such lights. Something to consider: a low amplitude, unmodulated microwave does not do much, increase the amplitude and it will cook your food. Another consideration might be how diodes work. AC current applied to a diode creates unidirectional pulsing DC current. This is certainly different from natural sunlight and even other light emitting devices. Do LED grow lights have different wattage out put ratings? As well as differing frequency bands? Certainly the material from which a LED is made will determine the frequency (spectrum) of light emitted.

Maybe a light-emitting rectifier(s) would create a more useful light for plants, but then power usage would increase considerably.     

Just some thoughts that I thought might be helpful. Or questions to ask the distributers of the LED grow lights.

[Steve Garvie]

Robert, the wattage of a light source is a rather poor indication of the “photosynthetic effectiveness” of that light source as artificial lights variably squander much of their power input through heat generation. LEDs produce less heat than fluorescent or metal halide lights but the lumen value or wattage on the box of an LED light unit is not a good indication of its plant growing power. The best measurement of “plant lighting” is the PAR output which is measured in micromoles of photons per square metre per second (within the wavelength range of 400-700nm) unfortunately most lighting units don’t come with a PAR score.

The other issue which I didn’t mention is light intensity reduction with distance. The intensity of light is inversely proportional to the square of the distance from that light. This means that if you double the distance of a plant from the light source this will reduce the light intensity to a quarter of what it was. As LEDs run a lot cooler than other light sources it is possible to reduce the distance between the LED and the plant thus increasing light intensity without scorching the plant.

[Robert]

Hi Steve,

I'm not likely to use artificial lighting, however the information is quite interesting. Thank you for sharing. I will look into this more as I can.

[ArnoldT]

Veltheimia bracteata in full color and two similar Lachenalia.

I enjoy the gentle blending of the colors on the Lachs.

Lachenalia callista
Lachenalia aloides quadricolor

[PaulFlowers]

The colour of this cyrtanthus is unbelievable: the photo doesnt quite capture it.

[Gail]

The colour of this cyrtanthus is unbelievable

Really nice flower shape too.

[Véronique Macrelle]

nice this Cyrthantus !

it feels very good in my greenhouse  now!

 Gladiolus tristis, sown in January 2016. it is very pleasantly scented.
 one on this  Gladiolus, among this seedling has bloomed in 2017, the year after sowing; its foliage seems to remain smaller (70 -80 cm approximately), finer too.

 Freesia xanthospila (syn Freesia caryophyllacea?) Bulblets were received from the srgc in January 2016 and have been waiting this winter to produce leaves and flowers. they supported -7 ° C in the greenhouse this spring.

[ArnoldT]

Gladiolus longicollis

Sweetly scented of carnation and clove pollinated by night flying moths

Found SE Cape

[Véronique Macrelle]

apart from the scent, it seems that Gladiolus longicorni looks a lot like Gladiolus tristis ...
 what are the differences?

[ArnoldT]

Veronique:

Here are some images of both.

  https://www.pacificbulbsociety.org/pbswiki/index.php/Gladiolus_tristis
https://www.pacificbulbsociety.org/pbswiki/index.php/Gladiolus_longicollis

Gladiolus longicollis Baker is a species found in a wide area of southern Africa, including the southern Cape, the eastern Cape, the Free State and the Northern Province. There are two subspecies. It has pale yellow to white long tubed flowers that are either uniformly colored or mottled with brown. Flowers are night blooming and sweetly scented of carnation and cloves. The first three photos from Cameron McMaster and the next two from Mary Sue Ittner. Photos three thru five were taken at Naude's Nek. The last photo from the book Plants of the Klein Karoo courtesy of Jan and Anne Lise Schutte-Vlok. They describe it as growing up to 60 cm tall with narrow cylindrical leaves and flowers with red brown spots and lines. The anthers are not much exposed, a characteristic that helps distinguish it from a similar looking Gladiolus tristis.

[Véronique Macrelle]

why, Arnoldt, yours is now blooming in the Northern Hemisphere while it is said to be growing in the rainy summers?
  G. longicollis is normally summer growing, right?
 I think to have some germination of G. longicollis from seeds srgc 2017-2018