Herb Seedlings will thrive under the correct Grow Lights

Spring is Approaching fast!

 Things to Consider for Spring

• Germinating Your Own Herb Seeds

• Ordering Potted Herb Plants

• Controlling Garden Pests

• Composting - Using Compost

• Drying and Storing Your Herbs

• Soil Fertility - Soil Testing Your Herb Garden Soil

• How the Changing Weather Will Affect Your Herb Garden

Natural sunlight, artificial light and herb plant growth

Vegetative growth of the leaves of herb plants is, for the most part, controlled by light. Of all of the limiting factors in photosynthesis, light intensity is the most important. Foot candles is the standard unit used to measure light intensity. The intensity of the full sun on a clear day is about 10,000 foot candles. Indoors, even near the sunniest window, that figure drops to 500 foot-candles or less.

• Herb plants grown in little or no light have small leaves, overly long stems, known as being "leggy," and are yellow in color because no chlorophyll in the leaves is formed.

• As the light is increased the stems grow shorter and the leaves increase in size but are still yellow from lack of chlorophyll formation.

• Increase the light a bit more, while the size of the herb doesn't change, the leaves will begin to produce chlorophyll and turn green.

Photoperiodism is the length of time a plant is exposed to light. The required intensity artificial light needed to grow herbs varies according to the length of time the herb plant will be under the lights. The lower the intensity of the grow lights, the longer the light over the herb needs to be lighted. The critical light period per day for most plants to produce adequate growth is 14 to 16 hours.

The light that is received from the sun consists of a small percentage of ultraviolet, about 1/2 in the visible range and the rest is infrared. The only part of this light needed for photosynthesis comes from the visible spectrum which consists of Violet, Blue, Green, Yellow, Orange and Red.

• Florescent lights produce the visible spectrum and ultraviolet but no infrared.

• Incandescent lights produce the full visible spectrum and infrared but no ultraviolet light .

Used in combination they produce limited but adequate light if they are kept close enough to the plants.

Grow Lights of the correct type will extend your Herb Gardening Season

There are three basic types of grow lights available to the home herb gardener:

1. Fluorescent Grow Lights- They produce the lowest light intensity but with little heat - they are inexpensive and readily available - can be home-made or purchased complete - They need to be very close to the herb seedlings to provide adequate light intensity.

2. High Pressure Sodium- Do not produce the complete spectrum but very good when some ambient light is available - They produce excessive heat  - Can be expensive to purchase - heavy to handle.

3. Metal Halide- The most full-spectrum so they are the best choice when no ambient light is available - Also produce excessive heat and must be kept some distance from plants - They can be expensive and heavy.

Good quality lighting for raising top-quality herb seedlings by the home-owner can be had using readily available fluorescent grow lights. Ordinary 40 watt cool-white or warm-white fluorescent tubes, like ones found in an over-the-counter 48 inch shop light, and incandescent bulbs can be used in combination.

In the latter example, a combination of two fluorescent tubes and three incandescent bulbs may be used to produce the correct color-spectrum. Fluorescent lights are rich in blue; incandescent lights are rich in red. Combine them and you get a good approximation of sunlight. Although this combination offers good quality color, its intensity does not approach that of direct sunlight.

The ratio in Wattage of fluorescent to incandescent light is about 3-to-1

If each fluorescent fixture is 48 inches long, the four 40 watt bulbs offer a total of 160 watts, producing about 600 foot-candles of cool illumination, still a long way from the 10,000 foot candles produced by the sun. This is the absolute minimum for growing healthy seedlings.

The added incandescent light is needed in much lower level so balance the fluorescent light with only three 15-watt incandescent bulbs.

Fluorescent Grow lights will produce the artificial light for raising vigorous seedlings

Purchase two double fluorescent fixtures or shop lights, three surface-mount sockets for the incandescent bulbs, a length of 14 gauge electrical wire, a plug, a switch and some wood and assorted fasteners. Enlist the help of an electrician or someone else competent in electrical wiring.

• The two double fluorescent fixture, combined with three incandescent bulbs will boost the light levels well above the minimum 600 foot-candles needed for good herb seedling growth.

Arrange a method of conveniently raising and lowering the bank of lights, keep the lights on 16 hours each day, occasionally dust off the bulbs so every bit of light gets out, and you’ve created a winter herb plant paradise.

A simpler alternative would be to order a set of inexpensive fluorescent grow lights from a reliable garden supplier. A typical example is the 48 Inch Model Table Top Plant Grow Light from Park Seed

Thomas Kueny, Publisher - www.growing-herbs.com