Overwintering Coleus: Placement and Light

It is officially the end of summer at Rosy Dawn Gardens. The coleus that were not fortunate enough to make it into the greenhouse are charred by frost and hanging limply over the sides of their pots. Inside the greenhouse, life goes on in colorful splendor, defying shorter days and cooler temperatures. Fall invariably brings a flurry of emails from our customers asking if there is a way to overwinter their coleus. So... What do you do if you do not have a greenhouse but you can't bear the thought of letting your beautiful coleus succumb to the the ravages of winter?
I won't sugarcoat it - keeping coleus in the house can be a tricky proposition. All the things that coleus love in the winter are in short supply inside the average home: good light, humidity, and good air circulation. It can be done, however, and many people do pull it off successfully by creating, in their home, the atmosphere that coleus need. Some people devote a whole spare room or basement area to their tender annuals, and some can only find a single window or corner of a room to spare for the cause. Either way, the goal of keeping the coleus alive until spring can be achieved.
The first consideration has to be light, since window placement is often the primary factor when deciding where your coleus are going to spend the winter. Unfortunately, windows in the average home seldom provide the ideal environment for coleus. If you place the coleus too close to the window they may be subjected to drafts and injured by contact with cold glass. Often there are heat vents in front of windows which can blast the coleus with hot, dry air. Windows often provide inconsistent levels of light. Your coleus could sit in relative darkness during the early part of the day and be blasted by too much direct sun in the afternoon. Plus, the coleus have to be very close to the window. Positioning your coleus a mere 12-18 inches away from the glass may not provide enough light for good health, even at the brightest point in the day. Despite the reputation of coleus as a shade-loving plant, they will not thrive in the low light conditions of the average home and, at best, lean and stretch for the light and become spindly. The simplest answer to this problem is to provide artificial light to supplement or substitute for natural light.
There are a number of options when purchasing artificial light. No-frills, 48" fluorescent shop light fixtures are very inexpensive at hardware and home-improvement stores and are the best buy for the amount of light you get. They can be suspended on chains, affixed to a stand, or set up between two stacks of bricks or other sturdy, non-flammable material. Standard fluorescent bulbs are economical and will do the trick for a few months indoors, or you can use the more costly grow-light bulbs for a full spectrum of light. I would definitely recommend grow-lights if your indoor growing situation is permanent. There are other types of grow-light fixtures available in all sorts of sizes and configurations, ranging from little light strips that can be mounted under a cupboard to stand-alone fixtures like goose neck lamps. Spotlights can be ceiling-mounted, but most grow lights have to be within a few inches of the top of the leaves to be effective. The most deluxe (and costly) option is a ready-to-use indoor gardening center that has one to three levels and all of the bells and whistles for growing coleus and other tender plants inside the house. One could build a similar set-up with minimal carpentry skills and some ingenuity. For many years before erecting our first greenhouse I started seeds and overwintered tender plants under homemade banks of lights in the basement and in other nooks and crannies in the house. I found it preferable to have free-standing fixtures and be independent of our limited windowsill space. Grow lights can also be used to supplement natural light in front of a window or door wall. Suspending or supporting fixtures above your plants will give you the ability to provide your coleus brighter light on cloudy days and extending the short days of mid-winter. There are other types of grow lights on the market as well. The newest type are energy-efficient LED grow lights, and if you want to make the investment it would be a great way to go. I have never used them, so I cannot offer instruction on how to use them. Comments from readers would be welcome!
If a windowsill is your only option, then you have to make do. Coleus have been kept over the winter for generations in a kitchen window, sometimes as nothing more than a cutting in a jar of water. It may not have been the loveliest of creatures come spring, but the coleus survived to see another summer.