Clearance needed under lights?

[AKNicolle]

I've got a bunch of fluorescent lights above trays in a room in the basement, currently providing lighting for my tropical bonsai, cacti, and soon some veggie seeds. There are five sets all told, each containing three T-5 full-spectrum tubes. From what I gather, they should be suitable for orchids.

My question is about clearance. The photo attached shows the clearance I have for three of the five trays. It's about 1ft or so between the tray and lights. The other two have closer to 2 or 3 ft clearance.

How much space would a typical orchid need? The lower lights would probably be fine for miniature varieties, but I'm new to this whole thing and have no idea how tall the flower spikes on orchids can get.

Does the spike have to be under lights also, or only the leaves? Would certain varieties consider this to be too much light, or is it impossible to provide too much light under indoor lights?

Thanks!
Andrew

[Subrosa]

I haven't been keeping orchids that long, but I've been doing it long enough to get a chuckle out of the phrase "typical orchid"! In the past couple of months I've figured out that there's an orchid that will grow in any reasonable situation you can provide, the trick is finding the right orchid for the conditions. What format of T5 bulbs do you run, normal output or HO? It makes a big difference in the amount of light. I personally think that for orchids you might as well hang the light as high as practically possible and then place your high light lovers on stands or hang them to get them closer to the lights.

[AKNicolle]

I just discovered something interesting. Only one set are T5HO - all the rest are actually conventional T-8 6500K. The T5s are eye-searing to look at, so it appears there's a big difference in output! Would light be a concern for the T-8s, then?

[Subrosa]

Big difference is right! I don't grow with T8s , but here's a pic of my cold room. The Dendrobiums are within 3" or so of a T5HO with a top quality reflector on it. The Phals are actually located outside the cone of intensity, as even with the lights all the way up it would probably be too bright for them:

[orion141]

It really depends on the orchid species as to what distance you need to put them from the lights ( higher light species like cattle has can be very close as in 4-6 inches whereas phals should be 17-20 inches away). The spikes don't need to be under the lights.

[Miss_Cat]

On the contrary. Orchid spikes and flowers are photosensitive. So they will grow towards the light no matter what. Tall spiking plants will naturally need more headroom than short spiking ones. As Orion and Subrosa said, it all depends on the kind of orchid you want to grow.

[Paul]

While there are exceptions, the plant's leaves will often give you a clue as to the suitability of the light you are providing them.

Dark green -- We are conditioned to think that dark green leaves means a healthy happy plant. That is a fallacy. Dark green means that the plant is maximizing the amount of chlorophyll its leave can contain to capture every photon it can. This is typically a response to less than desirable lighting. The plant is, in essence, desperately trying to capture all the light it can.

Medium green -- The plant is receiving enough light energy such that it does not need to go overboard on chlorophyll production. Instead, it can afford to divert some of its resources to other pursuits like growing and flowering.

Light green -- The plant is receiving so much light, that it needs to invest far less in chlorophyll production.

Yellow-green -- While this can result from other conditions, when it is a light related issue it indicates that the leaves are approaching a light "overload" or possible danger zone. As such, when leaves attain that color, it is generally wisest to step down the light intensity (of the plant's proximity to the light source). As with anything, there are exceptions. Cymbidiums, for example, often do far better when given full direct outdoor sun to the point the leaves become very chartreuse in color during their growing season (summer).

I use mainly t12s in my plant rack. The light quality of the inches at either end of a 4ft fluorescent tube is greatly inferior to that produced by the rest of the tube. As such I consider it "dead space" and place few if any plants in those regions and only the plants are those which can endure very low light. I don't even place phals there.

My catts, or other high lighters, generally occupy center stage and are placed so that the leaves are within an inch -- give or take -- of the bulbs. Those plants that are much shorter in stature whose leaves are too dark a green get moved up closer to the lights by virtue of being placed on an upside down pot. Plants desiring lower light levels than catts -- like phals -- are simply placed so they are further from the lights (ie. not place on pots). Phals can often be located -- in my set up -- about 8inches below the bulbs.

Spiking plants are lowered (or lights raised up) as their spikes get close to the lights. Tall spikers like many of the Oncidium alliance can be a major hassle in this respect so I do not usually grow them. On those occasions when I have, once the spike gets too tall to remain under my lights, I would place the plant in a brightly lit window.

As with most anything, your results may vary from mine. The plants in question, the type of lights being used, even how new or old the bulbs are all factors affecting just how close your plants will need to be to the light source(s).

[kaede]

Thanks, Paul, very useful.