Planting Window Boxes for Shade
Gardening author Cassandra Danz calls window boxes "the gardens of New York." She offers suggestions for planting a healthy and attractive window box that will thrive in the shade.
Make sure your container has drainage holes so water won't sit in the bottom of the box and rot the roots of your plants.
Cedar is a good choice for window-box planters because it lasts a long time and is naturally rot-resistant. To make your wooden window box last even longer, place a plastic window-box liner inside it – just make sure it has drainage holes too.
To create a beautiful design for your window box, you'll need plants of various heights: tall ones for the back, medium-height plants for the middle and something trailing in front.
Trailing plants: Good choices include ivy, ivy-leaved geranium and nasturtiums. Plant near the front of the window box so they can cascade over.
Plants for the middle of the box: Consider impatiens, primroses in the polyanthus group and Primula obconica, spotted deadnettle (Lamium maculatum), poor man's orchid (Schizanthus pinnatus) or holiday cactus (Schlumbergera). Choose selections with complementary colors.
Tall plants: Coleus, monkey flower (Mimulus x hybridus) and dusty miller (Senecio cineraria) would work well at the back of a window-box planting.
Fill the planter half-full of a good-quality potting mix. Add the plants, starting with the front and working your way to the back. Fill in around the root balls with soil, making sure that the tops of the roots are just barely below the soil surface. Planting too deeply may cause your plants to rot. Add a slow-release fertilizer such as Osmocote, and mix it into the soil surface.
Mount the planter securely in the desired location, and water well.
There are a variety of window boxes to choose from. Redwoods are attractive, but they tend to dry out quickly. Terra cotta window boxes keep the soil from drying out and hold salt and chemical deposits away from the soil. There are even self-watering window boxes available, with a hole in the side for water so you never need to water the soil. Plastic window boxes have the advantage of being the lightest to carry and install.