Winterizing Window Boxes

The dog days of summer are but memories and as fall settles in we all face the perennial challenge what to do with our window boxes with winter on its way. From experienced green thumbs to container gardening initiates, the decisions are always tough ones. Unless, that is, you live in one of North America's extreme temperature zones where the decision is made for you. By the way, if you are new to container gardening, or are planning to start - check out the many options at The USDA temperature zone of your location is a guide to the lowest temperature your window box plants can tolerate. But it is just that - a guide. Window boxes are particularly vulnerable to freezing and thawing, even in temperate zones where 10-20deg.F are not uncommon in January and February.


With this in mind, your winter plans should first consider general practice for your temperature zone. Next, and this is where decisions get tough and experience matters, you should consider your own microclimate - the way your local landscape can affect your weather. General practice should range from "over wintering" in the case of extended cold periods, to relocation of window boxes into sunrooms, or temporary insulation of the entire window box and its plants during a short cold snap. Over wintering means removing your plants from the window box and making rooted cuttings. Pelargoniums, for example can be lifted from the box, trimmed to within three inches of the base, then replanted in a temporary container and kept dry and at the lowest temperature they can tolerate. Too much moistness and warmth will promote premature growth. Relocation is an option where you have a sunroom available or a greenhouse. This is best in areas where temperatures are not extreme and cold periods still provide reasonable amounts of sunlight. If you (or your local weatherman) have a good record for predicting the length of cold snaps in temperate zones, you can always bundle your boxes and plants up in plastic or, better yet, a burlap bag with straw. Be sure to cover the bottom of the box as well since cold air can quickly freeze the soil. The look may not be elegant - but the solution works for brief cold or freezing temperatures. And so to microclimates - If you live in San Francisco you know exactly what this means.


Homes on the slopes on the Pacific side of the twin peaks can experience chilly, fog-laden winds, while on the other side the hill and towards the Bay it can be warm and dry at the very same time! Being aware of your local topography can help you and your window box better survive the impact hills, plains, ridges and lakes can have on general weather conditions. There's even more.


Your own neighborhood can have its little weather patterns, just consider the difference in temperature on either side of a north facing house on a clear, sunny but chilly winter's day. Of course there is yet another option, window boxes designed to hold pots. The look is great, but you can always remove the pots if the weather suddenly changes. Now, armed with the knowledge of your USDA temperature zone and your own local meteorological idiosyncrasies, you can plan your winter window box. In the southeast, for example, warm spells result from humid tropical air that often brings rain with the higher temperatures. Yet within days, a "Canadian Clipper" can rush south with frigid and very dry air. Even when armed with your weather knowledge it makes sense to plan your winter window boxes with plants that can handle the changes as opposed to summer when anything goes and grows. North facing boxes are best with shade tolerant varieties such as Camellia, Ajuga, and Hydrangea. South facing boxes in colder dryer periods are good for varieties better able to tolerate lack of water (and we all know that watering is always an issue with window boxes), Agapanthus, Ficus, Yucca are examples.


One last tip, the Internet is THE place to research container gardening and buy window boxes. One of the widest selections to be found is located at