Indoor Lighting

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Charlie:
This is a big topic that can involve a lot of technical stuff, but we will avoid that for now and just take a quick look at the question of what type of lights are available for growing hibiscus indoors.

You can grow hibiscus indoors, and winter is a good time to experiment with it. The hibiscus are warmth loving plants and being able to grow indoors where it is warm is what they crave in winter. However, they do need some light as well as warmth and that is where the problem comes in for some people.

Light can do 3 things for hibiscus - it can keep them healthy and green, it can help them grow, and it can help them bloom. It takes less light for the first, and increasing amounts of light for the last 2.

It helps a lot if there is a place to put hibiscus near a window that gets a lot of winter sunlight. In some situations such as in our house, the lower sun in winter angles directly into some of our windows. In summer it is higher in the sky and does not directly enter the house. In winter the hibiscus we place in those windows actually blooms, while in summer all they can do is grow in the bright indirect sunlight.

If you have a sunny window you may not need any extra light on the hibiscus at all. If no sunny window is available then some extra light will be needed. It can be as little as a regular lamp nearby. This is not a lot of light but it will help the hibiscus stay green and healthy.

To see growth or blooms in the winter more light is needed. Here is a chart that tells the types of light that are helpful. Unfortunately, the better the light, the more it costs, but that's life, it seems.

1.  METAL HALIDE LAMPS - This type of light is blue-orientated in the spectrum. It is the best type of light to be used as a primary light source (if no or little natural sunlight is available). This type of lamp promotes plant growth.
2.  HIGH PRESSURE SODIUM LAMPS - These lamps are red/orange in the spectrum. They are the best lamps available for secondary or supplementary lighting (used in conjunction with natural sunlight). This" type of light promotes flowering/budding in plants. It is ideal for Greenhouses/Commercial growing applications.

3.  CONVERSION LAMPS - There are two types:

          A.  Sodium Lamps which run on halide ballasts - more common.
          B.  Halide Lamps which run on sodium ballasts.

This type of lamp allows you to tailor the light source to the growth stage of the plant (again using halide blue light for growth and sodium red light for flowering/budding) merely by changing lamps.

4.  FLUORESCENT - This type of light is perfect for starts and seedlings but is a poor light source for growth and budding primarily because of low lumen output.

5.  INCANDESCENT - Does not require a ballast. These lamps consist of Sylvania Spot Gro R-30 and R-40 flood lamps available in 75 watt and 150 watt. Also good for starts and seedlings. Good lamp for individual plants or small groups of plants. Provides an inexpensive alternative to HID lamps (Halide and Sodium lamps are referred to as High Intensity Discharge Lamps).

Charlie


Charlie:
Bart writes to ask if the incandescent Spot-Gro lights he has are good for growing hibiscus. My reply might be helpful to others wondering the same thing. Here it is:

Those lights are made to give a pleasing (to people) light when pointed at plants, and they do make foliage look nice. They are not efficient for growing plants. Like all incandescent lights they put out more heat and less light than other types available. Since the heat prevents them from being too close to plants the light they provide at the leaf level is less than it should be. With that said, they are still a lot better than no light and will provide some energy that the plants can convert to carbohydrates by photosynthesis. Most people prefer going with cf bulbs nowadays (compact fluorescent bulbs) when using a standard light fixture for growing. In both cases having a directional reflector aimed at the plants helps increase the light levels.

None of the bulbs that standard light bulb companies label "grow lights" are significantly better for growing plants than standard bulbs. This is because plants use light that is at both ends of the visible (to humans) spectrum more than they do the middle of the spectrum. It is difficult to make a bulb that increases just the top and bottom of the spectrum so real grow lights concentrate on either the blue end or the red end of  the spectrum. Such light appears odd to human eyes, particularly the red end of the spectrum, so normal bulbs are not made that way because no one would buy them for use around the house. However, for growing plants, such bulbs are available with some suppliers making room in the light fixture for both types of bulbs so that the entire spectrum is covered. In situations where there is a little daylight available then the grower only needs to supplement with light from the red end of the spectrum which promotes flowering. If there is no natural light present growers use either bulbs on the blue end or a combination of both types.

The real problem with all this is cost. All light types except for incandescent need a separate ballast to operate. In the case of real grow lights, these are expensive, big, and heavy. They provide a great deal more plant-usable light than other types and use less electricity per unit of light than other types but the initial cost is high. Not surprisingly, the worst type of lighting for plants is the cheapest - that being incandescent like the Gro-Spot - next in expense and amount of light are fluorescent bulbs, and finally the most expensive but best light comes from HID High Pressure Sodium and HID Metal Halide lamps - cost $250 to $500.  With lights you get what you pay for.

To keep hibiscus alive and green you don't need the most expensive lights. To get them to bloom in winter you probably do need the expensive ones. I haven't tried it but I think you will get some growth with the cheaper lights but not as much as with better lights and it might be a little stretchy, too. A lot depends on that window you are planning to install. If it is south or west facing it might let in enough sunlight so that supplemental lights are helpful but not critical and the cheapest ones will be plenty.


Charlie

Louis:
Hi All,
i would like to add my 2 pesos in the discussion,

i have my plants in a large bay window during the day and brought into the room at night, then close the drapes on the window to keep the coolness out.

on a sunny day, the plants get direct sun from 10 am till 3 pm and after that, i light some supplemental lights, which are the 150 watt grow lights. they supply the needed extra light and also some additional warmth. it seems to be working for me, because the plants are in bloom, with numerous buds and lots of new growth coming up.

i do have a greenhouse but i don't use it because of the cost to heat it.

i was using it back a few years ago but stopped when out rates doubles. gotta love the utility companies :(

Louis

Charlie:
Hey Lou,

Those big windows are a real plus for your hibiscus. The warmth of the house plus some decent sunlight = wintertime flowers!

One contrary thought is that from time to time most hibiscus need some degree of pruning to look and perform their best. I'm not suggesting you cut back your blooming stems now as long as they look good but in the long run I think you will be most satisfied if you use some judicious pruning when the timing seems right. For instance it is not uncommon for a stem to grow long and lose a lot of the lower leaves so only a bare stick with some leaves and buds at the top remain. Cutting such a stem from 2/3 to 1/3 back is the best way to get it to leaf out again and often to get more than one branch growing back as well.

Thanks for the dos pesos..

Charlie

Charlie:
Speaking of indoor lighting, Bart H from Kentucky is trying an interesting experiment this winter. Since he has no good indoor place with windows to overwinter his hibiscus (no wifely approval either!) he decided to grow them in his garage. First problem - no heat and too big to heat economically.

To solve the heat problem he built a simple cube shaped room inside the garage. He also put a ceiling on it so that it is fully contained and separate from the rest of the garage. When a room is airtight and not too large even a small heater can heat it up quickly and efficiently. One the heater was added he had a grow room suitable for his hibiscus.

But, he decided to be more ambitious than just providing a way for his hibiscus to survive. He wanted growth and blooms. The only thing lacking was sufficient light. The room has no windows and the small spot lights he was using just don't provide the amount and type of light that plants need to grow and bloom. So, after consulting a light manufacturer we decided on a 1000 watt HID light that supplies light in the blue and red spectrums that hibiscus need to both grow and bloom.

This operation is up and running now, along with a lot of small refinements he has made to make it an automated operation fine tuned to growing and blooming.

Since he heavily pruned a lot of the hibiscus it will be awhile before we see if both the growth and blooming can be accomplished with NO real sunlight. Stay tuned, photos when available!

Charlie

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