It’s that time of year again. For those of you like me whose aquaponics system has been relying on the free plant lighting that Mother Nature provides, this is the time of year when you have to decide: to supplement or not to supplement?
The purist locavores will tell you that eating in season is part of the gig. That it is the pact we make with Nature to replace the joy of summer produce with winter squash and potatoes. To that I say ‘hogwash’! I don’t have to wash my clothes in a stream, I don’t have to churn my own butter or milk a cow, and because of advances in grow lighting technology, I don’t have to give up on tomatoes and peppers in the middle of the winter. (I apologize if that was offensive to my locavore friends!)
I supplement the shortened natural daylight that pours through my greenhouse with HID grow lights that come on at ‘sunset’ and go off at 9:00 p.m.. This allows me to grow not only the herbs and greens that do well in a day with the 11 hours of sunlight we are now receiving, but also grow the fruiting plants that crave the longer days of summer.
A recent exchange on our community site shows the confusion over the different types of plant lighting that are available today. I know a thing or two about grow lights, and recently gave a presentation on the subject, so I posted some thoughts. Members seemed thankful for the guidance so I thought I would share them here with you as well.
When you select and run lights for your plants consider:
- Duration - As I said above, how long you run your lights will depend on the day-length requirements of your plants. Are they fruiting (e.g. tomatoes) or foliage (e.g. lettuce) plants?
- Spectrum - Be sure that you are covering the blue and red spectrums that are absorbed by plants.
- Canopy penetration – The light should penetrate deep enough into the plant’s canopy to effectively get light to the lower leaves. A tomato plant has a very different canopy depth than a lettuce plant.
- Heat - Some light sources produce a lot of heat. This can be a good thing when you are trying to heat a greenhouse in the winter, but not such a good thing if you are growing in a small, enclosed room within your house.
- Energy input for light output – Some fixtures require a lot of power, some are fairly energy efficient.
- Cost - Consider all facets of cost, which include the original cost of the size fixture required to grow the plants you want to grow, the cost of the replacement bulbs, the frequency of replacement, and the cost of the power to run the light.
Below, I evaluate the 3 main types of lighting options favored by indoor gardeners using the parameters listed above.
Florescent Lighting using T5 bulbs – T5s are used in indoor lightingfixtures because they are skinny, so you can pack a lot of them into a fixture. As the number next to the ‘T’ goes down, so does the diameter of the bulb (T12′s are bigger than T8′s which are bigger than T5′s)
- Pros of T5′s – They have a broad plant lighting spectrum so they work for both fruiting and foliage plants. They are also low power use and don’t throw off a lot of heat.
- Cons of T5′s – They will only reach through 18″ of plant canopy. For taller plants (again, think tomatoes) you can put them up sideways. Also their performance drops off significantly after 6 months, even though they still look just as bright as the day you got them. You must replace the bulbs every 6 months of use.
- Pros of HID – They provide much more intense light that goes through almost any plant canopy. If you get a switchable ballast you can easily move from a high pressure sodium bulb (red spectrum for fruiting) to a metal hallide bulb (blue spectrum for vegetative growth) for an even more precise plant spectrum. Bulbs last at least a year.
- Cons of HID – The bulbs are expensive, they draw more power than fluorescents, and they throw off some serious heat.
- You might find this chart helpful in figuring out coverage if you decide to go down the HID lighting route…
- Pros of LED – no heat, very low power consumption, you never replace the bulbs
- Cons of LED – Because these are still new, I have not seen enough data to be confident that they will grow as well as either of the other two options and they are relatively more expensive at this time. Also they cast a very odd light over your plants and give a red glow to the room. A friend who has just started growing with LEDs uses a flashlight to actually see what her plants truly look like.
Here is another interesting chart I ran across recently that shows the light output of some different options…
I hope this helps you to make an educated decision about whether or not to help Nature out and extend your season too.