Perfect time to build windowsill herb garden

Marianne Ophardt, WSU Benton County ExtensionNovember 8, 2013 

Now that the outdoor gardening season has ended, gardeners don't have to be twiddling their green thumbs. Keep them busy -- grow a windowsill herb garden.

If you have a sunny windowsill, all you need is a waterproof tray and some pots that will fit on the sill, quality potting mix and herb plants or seeds. The herbs will do best in a south- or west-facing window that can provide four to six hours of direct sunlight a day.

You can go the fancier route and buy a special windowsill herb garden tray and pots. Some come planted with herbs. If you prefer to keep it simple, look for a long plastic tray that will accommodate several pots, or use pots with individual saucers. Make sure the tray or saucers are waterproof so you don't damage the sill. Pots should be at least four inches wide and 6 to 8 inches deep, with a hole in the bottom for drainage. I prefer glazed pottery pots, but plastic or terra cotta clay pots work too.

I recommend growing about three to five different herbs. Select the herbs that are easiest to grow indoors and ones you'll enjoy using to cook. Herbs that grow well indoors are chives, marjoram, parsley, rosemary, sage, thyme and winter savory. While sweet basil is a favorite herb of many gardeners, it doesn't do well in windowsill herb gardens.

You might be able to find small herb plants at local nurseries or buy seeds to start your own. Some start plants for growing indoors by root cuttings taken during the growing season from their outdoor garden herbs, like rosemary, sage, thyme and mint.

Next is quality potting mix. Don't use soil from the garden, because it is not sterile and it does not drain well. A quality potting mix for indoor growing has a blend of materials that hold moisture and provide drainage. I like ones that have a combination of peat moss, perlite, vermiculite or sand, and avoid those with lots of dark, partially composted organic matter.

Place a piece of screen or fabric garden mulch over the hole in the bottom of each pot, and then add some potting mix. Place the herb plant with its loosened roots into the pot and fill in around the roots with the mix. The base of the plant should be at the same depth as it was in its previous pot. Leave about a half-inch of space between the mix and the top of the pot. This will allow room for watering. (If planting seeds, follow the directions on the seed packet.)

Once your plants recover from transplanting and start to fill the pot, snip off leaves whenever you need them. Trim your herbs occasionally to keep them neat and tidy. Leggy growth indicates too little light. If your potting mix contains fertilizer, you shouldn't need to fertilize your plants for a while. If not, use a water soluble houseplant fertilizer.

Keep the potting mix moderately moist. Most herbs do best when the soil is not wet. Monitor the moisture in the pots frequently, using your finger to check below the surface. (Note that mix in terra cotta pots will dry out more quickly.)

-- Marianne C. Ophardt is a horticulturist for Washington State University Benton County Extension.

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