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Grow light #780561

Asked January 21, 2022, 9:47 AM EST

Before moving out of the country, my neighbor "bequeathed" me this grow light that he had used with his orchids. I know nothing about it - not even the brand/manufacturer. Before I (try to) use it, I have a few questions: 1. Do you recognize this product and Is it of good quality ? It seems rather "old school," what with an incandescent bulb. 2. If I were to use it - let's say with succulents - what is the appropriate distance between bulb and plant? 3. Should I be concerned about the amount of heat that the bulb will undoubtedly produce? 4. Links to articles with information not raised in my questions will be appreciated. Thank you!

Montgomery County Maryland

Expert Response

We don't recognize the specific product, but based on the bulb size and fixture design, it appears to be a type of high-intensity discharge (HID) lamp. They aren't as commonly used by home growers as fluorescent or LED lamps, but serious hobbyists (of orchids, among other plants) and greenhouse growers can use them to boost plant lighting. They can be used in conjunction with natural light or used by themselves. In general, HID lights are more intense and generate more warmth than fluorescents and LEDs. They also use more electricity, though their energy-efficiency isn't bad.

There is a series of articles about artificial lighting on our blog which are being published about once per month; there will be four parts to the series in total, and the third will be publishing by the end of this month. This third installment happens to be the one discussing lamp types and technical terms dealing with light measurement. HID lights are mentioned but not reviewed in much detail since they are rarer and may take a more specialized setup in terms of using a ballast (more so for higher-power HIDs), accommodating the warmth they produce, and securely anchoring the ballast unit and light unit due to weight of the metal housing on each. The series as a whole provides an overview of artificial lighting with regards to types of light output and how lighting impacts plants. You can find the beginning of the series here: https://marylandgrows.umd.edu/2021/11/29/an-introduction-to-gardening-under-lights/

If you are wary about using it or think you won't need a lamp that powerful, you may be able to find an interested buyer (or someone to donate it to) in a local orchid group or among other plant hobbyists (vivarium keepers, aquarium keepers, hydroponics growers, etc.).

The main benefit of HID lamps is that they provide light to a larger square-footage area and allows you to grow taller plants underneath it, since the intensity of the light allows foliage to sit further from the bulb and still receive lots of light energy. (Some orchid flower stalks, for instance, can grow a few feet higher than the foliage, so they need lots of "head room." Lower-power lamps won't provide enough light energy to foliage placed that far away from the tubes/bulbs.) Aside from certain orchids, higher-light loving houseplants that would benefit include succulents, air plants and other bromeliads, and edibles overwintering inside (citrus, herbs, bay leaf).

Even so, depending on the output of this particular unit, it's likely foliage shouldn't come within a couple feet of this bulb so it's not too intense. Exactly how close or far it needs to be positioned will depend on what you measure its output is. Perhaps the base of the bulb, when unscrewed, will still be printed/stamped with the wattage. 400W is commonly the low end of the range of bulb power for HIDs. Otherwise, you can get a ballpark range of light brightness by measuring the lit bulb's output with a light meter (usually in footcandle units). Some phone apps can do this crudely, and there are ways to use cameras or dedicated handheld light meters to measure it as well.

If you don't have a way to measure light output, start by placing the succulents several feet away and gradually move them closer (perhaps around six inches at a time once a week so they have time to acclimate) until they start to show signs of light stress. This can manifest in different ways depending on the plant species, but signs include foliage turning more red or purple, leaf internodes (the distance between leaves along the stem) becoming shorter as the stem grows, or more explicitly, a "sunburnt" or "bleached" look that damages leaf tissue, causing tan areas and a dried texture. Injured foliage cannot heal, but in correcting for over-lighting by moving the plants back a bit, new growth after that point should remain undamaged. Plants that are not actively growing new foliage may not be able to acclimate fully until they resume new growth, since leaves have a limited capacity to adjust to changing light levels.

Given these bulbs draw more amps from a household electric circuit than fluorescents and LEDs, to be safe, make sure you don't use it on a circuit that already powers high-draw appliances. HID lights are also warm enough that cool water splashed or sprayed on the bulb might cause it to shatter, so keep this in mind when deciding on where and how to hang the fixture. Some HID fixtures come with a glass plate that is held in front of the bulb as a shield from this temperature shock, but it doesn't look like this unit has one. In either case, if used in a smaller room or one with limited airflow, expect that running this unit several hours a day may raise the room's temperature by several degrees.

 

Miri


Miri:

Thank you for your response.  So interesting that it was you who responded: I just read your "Maryland Grows" post of Dec. 29 about light levels; that's what prompted me to get around - finally!! - to ask about this light.

All things considered, I am going to offer it to other gardeners and look for a less intense grow light for my succulents - one that is not as energy-thirsty.

Thanks again.

Howard

On Fri, Jan 21, 2022 at 1:50 PM Ask Extension <<personal data hidden>> wrote:
The Question Asker Replied January 21, 2022, 3:11 PM EST

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