Hello, I got a boxwood shrub in a planter about a year ago and placed it at my front porch (gets some sun but not full sun). It now looks a bit brown. Do I need to something besides regular watering, or will it get better on its own? Thanks
Thank you for contacting the Toronto Master Gardeners concerning your potted boxwood. There could be a number of reasons why your boxwood is exhibiting brown leaves. Drying winter winds, lack of water before freeze up, lack of drainage in the container, fluctuation in soil temperatures are just a few of the environmental factors that can affect container grown plants.
Unlike deciduous woody plants which go completely dormant during winter, evergreens do not; they slow down, but they still “breathe” (transpire). The needles/leaves still need moisture from the roots, especially if they are being dried out from winter winds and/or afternoon sun. Yet once the ground freezes plant roots are not able to take in moisture from the soil. Therefore, you want to make sure that the roots of your boxwood have as much reserve moisture as possible going into winter; do not stop watering them until freeze-up. Then, place a thick layer of mulch over the soil to keep it all nicely insulated.
You want to avoid sudden warming; site the planters away from vents and any spot subjected to reflected heat (e.g. immediately next to a light-coloured wall facing south or south west). This will cause the leaves to transpire and lose more water.
Containers must have drainage holes in the bottom, and must be at least 5 cm wider than the original nursery pot, This ensures that there is enough soil around the roots of your plant to provide insulation and minimizes sudden fluctuations in soil temperature.
You can add a layer of compost to the top of your planter and work it in gently, be careful not to damage the surface roots. This replaces nutrients that might have washed out of the container. Eventually, you might have to repot a boxwood, but it depends on the variety you choose and size of the container. If you notice the growth of your boxwood slowing down, it is time to repot.
As the spring progresses, check for new buds. Once they start developing, you can cut back any damaged or dead branches. Boxwood takes to light cutting and shaping quite. The best time to prune boxwood is the beginning of June. I usually shape my boxwood the first week of June. never prune boxwood after mid-August as they will not have enough time to harden off before winter.
The new York Botanical Gardens have and excellent article on Boxwoods and the Missouri Botanical Garden article on Growing Evergreens in Containers provides some general information.
Lastly, the Toronto Master Gardeners Garden Guide on Container Gardening provides some useful information.