Grrowing Medicinal Herbs Under Artificial Light
Answered by: Conrad Richter
Question from: Lindsay Buffington
Posted on: January 10, 1999

I’m a student doing a year-long research project on the effect of different types of light on the growth of medicinal herbs. Before I begin my experiment, I have a few unanswered questions that I can’t seem to find the answer to anywhere.

Here are my questions:

1. How intense is artificial light compared to natural light during the winter and early spring months?

Artificial light can be stronger or weaker depending on the artificial light source and how far it is away from the plants. Most household light sources such as incandescent and fluorescent lights are weaker than outdoor summertime light. And they are usually much too far from plants. It is worth noting that light intensity drops to one quarter for every doubling of the distance. Check the Richters website ( in the Magazine Rack section for an article on growing herbs indoors and the lighting systems required.

2. From which direction does the sun shine the strongest during the winter and early spring months?

From the south.

3. Approximatley how many hours of direct sunlight does the eastern shore of the USA receive on a regular basis during the winter and early spring months?

Don’t know. The local weather office should be able to get you information. The local cloud cover is important.

4. How long does it take for most medicinal herbs to sprout from seed?

1-3 weeks.

5. Which types of medicinal herbs grow fastest, strongest, and healthiest indoors?

Not many do well indoors unless you have excellent lighting such as that provided by the high intensity lights (see the article referred to above). Gotu Kola, sheep sorrel, comfrey, are some possibilities.

It is important to realize that scale is an issue with many medicinal herbs. It may be possible grow certain herbs indoors but can you grow enough to make the effort worthwhile. You also need to consider whether the herb requires more than one season to reach maturity, and whether or not it normally enters into winter dormancy: many hardy perennial herbs require a winter freeze once a year to do well.

6. What type of soil is best for growing medicinal herbs from seeds indoors?

Because you will be growing in containers the soil requirement is automatically different from what is needed outdoors. This is because of the need for better drainage. Look for a good potting soil that is made with compost and some top soil; avoid mixes made with mostly peat moss supplemented with fertilizer.

7. What type of container helps medicinal herbs grow best indoors?

This depends on the type of medicinal herb you are growing. Root herbs such as valerian and echinacea need deeper containers, while leaf herbs such as catnip, gotu kola and sheep sorrel can do with less deep containers. (Valerian and echinacea grow too tall to be worth the bother of trying to get them to grow indoors – I mention them here to make a point because they are well known root herbs.) Generally, a good container is at least 6 inches deep and has lots of drainage holes.

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