Some of us just can’t bear to say good-bye to all our herbs during the fall harvest. Although I have bottles of dried herbs and plenty of pesto in the freezer, I still have some pots of basil in a southern exposure window and a number of herbs downstairs under “the lights”. As the sunlight gets lower and weaker in our part of the world the poor basil are straining toward the windows. Time to give them some artificial light to help them out.
Most herbs respond to fluorescent lights and my favorite are full spectrum lights. Full spectrum lights have a closer light profile to sunlight and the plants seem to enjoy them just a bit better than regular fluorescents. Although I have used the regular ones in years past and one herb in particular doesn’t seem to mind. I have a pot of lemongrass that is several years old and it doesn’t seem to care if the light is full spectrum or not, as long as it is directly over the plant. Most herbs do like bright lights but they need a little rest too. Putting a timer on the lights to give the plants about 8 hours of dark seems to work for me.
A new light that is quickly becoming more affordable is the colored LED. I just looked at a panel online for $27 (plus shipping) that will cover a 6 square foot area. Plants really respond to the blue and red LED lights. The blue lights are more for vegetative growth and the red ones are more for flowering. The cool thing about these lights are that they are literally cooler, so they don’t overheat your plants. And they last longer, and they use less electricity. I’m headed in that direction, but it is hard to just toss good fluorescents when I have them and they are working.
The most difficult part of keeping herbs indoors is figuring out when to water. Regular watering is good, but most herbs do not like soggy roots. Rosemary is a prime example of this. The more you water rosemary, the drier it looks until it turns brown and dies. The best test for watering is the finger test. Stick your finger into the soil and water when it is dry an inch down. Rosemary might also like sitting on top of pebbles so the bottom of the pot is not soggy either. And it does like cooler temperatures – 60°F to 70°F. Basil likes more water. But they will tell you right away. If they start showing signs of wilting, it is time to give them a good long drink.
Be on the lookout for pests. They love it when you crowd to many pots into to small an area. (Ask me how I know.) Spider mites and mildew can quickly become a problem in an over crowded area. Air movement really helps too. Not a full on blast, but a small clip-on fan placed far enough away to create a gentle breeze.
I tend to fertilize with a water-soluble fertilizer only once a month or so, depending on the pot size and the plant.
Most of the herbs I have overwintered over the years do seem to slow down considerably, whatever I have done. I’ve stopped expecting to get regular harvests throughout the winter but it is a fun challenge to see if you can keep them alive until the greenhouse warms up in the spring.
If you have already harvested all of your plants, you might try propagating some from the fresh herbs you can buy at the store. I’ve placed a variety of herbs in water under my lights and watched them root, potted them and watched them grow. It is an inexpensive way to play in the soil during the winter if you need a little fix.