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#1 01.09.2014 09:19

David Schweden
Junior-Mitglied
Registriert: 07.06.2014
Beiträge: 9

Artificial light in winter (Kunstlicht / Beleuchtung)

I mainly wonder if Toby can tell us if he has a general approach to light in the winter which he applies in the greenhouse and can recommend? Or is it individual? Of course all input is welcome but there might already be some such threads.

I bought a 1½ m Rh Baueri and 1 m Cyphosperma from PPP which I put in a NW oriel (with two ~1 m Licualas, a Kentia and a Ch Elegans) and a small Lipstick palm which is in a big SW window (with a small Foxtail, Footstool and Ph Roebelenii), and I want them to at least stay green but preferably have moderate growth in the winter.

My main plan is to this week buy CDM (Ceramic metal halide) lamps 4200K with narrow reflectors (with an ordinary fluorescent, the top centimeters get much more light due to the beam width, and also are hard for me to place, and the long distance with reflector keeps the heat down), 2 per group of plants (so that no fronds are shaded by others) and turn the "bushy" palms 1-2 times/week. For the oriel I have 5 klx in mind (150W for 1,5m diam) and for the SW window 20 klx (70W for 0,5m diam). Temp in oriel will probably be 20-22C, in SW window 18-20C.

I read that many (e g Ph Roebelenii) do ok (but don't grow) just by standing next to a window without extra light and that you can even move them to a dark corner. I also read that the elongation that many plants can have if low light or red/yellowish light (like high pressure sodium or 3000K fluoescent) in combination with high temp, does not apply to palms, so I guess I could get cheaper lights but I can't find any HPS with reflector (and fluorescent or LED would be too clumsy to get a narrow beam); ordinary Metal halide would be ok but are not cheaper and have less human friendly light.

I would hate to see fronds turn brown prematurely since I've gotten much better at handling my palms the last months (e g I killed a big Ph Roebelinii a few years back, but this one puts on a new frond per month, and my poor 10 year old Kentia has never been this happy).

I found these 2 related threads: 1 2.

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#2 01.09.2014 13:12

Hamal
Senior-Mitglied
Ort: Werl, Zone tC
Registriert: 07.12.2013
Beiträge: 1.304

Re: Artificial light in winter (Kunstlicht / Beleuchtung)

I do not face the same issues yet, as most of my palms are still small. When I had a number of planted aquariums, I used to work with compact fluorescent bulbs with aluminum reflectors. The reflectors could be bent to narrow or widen the beams. Above some tanks I used metal chains to position the reflector lamps as closely as possible to the surface. On some tanks I also used standard T8 fluorescent bulbs, which worked fine.

In all of my planted tanks I had tremendous growth and had to remove a bucket full of plants every week. So I cannot imagine that this will not keep your plants healthy and alive during the dark winter, maybe even provide some growth.

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#3 01.09.2014 14:12

David Schweden
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Registriert: 07.06.2014
Beiträge: 9

Re: Artificial light in winter (Kunstlicht / Beleuchtung)

Thanks. I agree ordinary "cold white" (~4000K) fluorescent or CFL are often a very good choice both for the plants, economically and to get an acceptable light color in a living area. However they have to be placed very close to the plant to get high illumination. Both CFL and LEDs are too bulky to fit in a reflector that gives a beam angle of 15-25 deg, which is what I want. So for me it is probably just metal halide and high pressure sodium that can do it, and among those, afaikt ceramic metal halide are the only ones with reflector and that come in a low wattage (most common is ~400W which is too much for me), and they also have the advantage of quite enjoyable light color (not as blue as normal metal halide). A couple of (minor) downsides are efficiacy (40-45 lm/W for 35-70W, not bad but is is more than double that at higher wattages) and since a ballast is required (and there's only one manufacturer) prices are not very low, about €250-300 per lamp and per ballast at the cheapest resellers. A bit hard to find too.

I hope Tobias will tell us what he finds works too, he must have an enormeous amount of experience.

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#4 01.09.2014 18:51

Hamal
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Ort: Werl, Zone tC
Registriert: 07.12.2013
Beiträge: 1.304

Re: Artificial light in winter (Kunstlicht / Beleuchtung)

David Schweden schrieb:

Both CFL and LEDs are too bulky to fit in a reflector that gives a beam angle of 15-25 deg, which is what I want.

Is there a special reason why you want this narrow angle? As long as the plants have enough light to stay healthy, I would be happy. Especially in Sweden, the winter days are short, so it must be a struggle to keep palms alive.

David Schweden schrieb:

high pressure sodium

My understanding is that sodium vapor bulbs emit light in a very narrow yellow spectrum, which is not what you want for plants. You need red and blue light, so the metal halide is what you want.

David Schweden schrieb:

I hope Tobias will tell us what he finds works too, he must have an enormeous amount of experience.

Yes, I hope so, too, even though he probably does not need to worry with the glass houses he keeps his palms in.

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#5 02.09.2014 08:55

David Schweden
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Registriert: 07.06.2014
Beiträge: 9

Re: Artificial light in winter (Kunstlicht / Beleuchtung)

The reasons for the narrow beam are: That the light shall reach all leaves not just the top & middle ones, to be able to place the lamps close to the roof not in the middle of the windows, and to get less heat on the plants. I also like the white light of CDM.

The difference between a house of glass and an oriel or being close to a big window at home is not necessarily that big, it is mainly a matter of number of hours of sun I'd say, so the difference can be <50% in total energy at least for me since I have big unblocked windows, and unless the greenhouse has very clean non-clouded windows, you can actually have more total energy in my home than in a greenhouse. I'm no expert on greenhouses but I think some have opaque windows which would decrease illuminance peaks well below the max of ~100 klx. In my home during direct sun I get 60 klx due to triple glass, even far into the apartment. But the PPP greenhouse is located further south than me which makes a difference in mid winter.

I read that HPS are the most widely used grow light for supplementary light when there's some daylight, also by professional growers. They need no ballasts which make them cheaper.

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