Gardening in Window Boxes

With only window boxes to garden in, it's amazing how clever some Oriental Bay locals can be. From my third-storey apartment, I look down on a small space between the wall of a house and a boundary wall. It gets hardly any sun and could be a drab little area.

But it isn't. The eye is drawn immediately to a long window box crammed full of red and white petunias. They positively light the place up. On the boundary wall itself are semi-circular wall pots also spilling over with flowers. A dull little area has been turned into an inviting, colourful entranceway.

Anyone who's travelled in Europe has admired the window boxes in the cities — scarlet geraniums spring to mind, brightening up those narrow city streets, like torches. In Wellington we have the added challenge of the wind, so David from

California Home and Garden often suggests low plants that don't catch

the wind so much. Included in his list are the sun-lovers: dwarf calendula, dwarf chrysanthemum, geranium, lobelias, French marigolds, nemesia, pansy, pelargonium and petunia. These plants are not tall enough to catch the wind too much.

For shady positions he suggests alyssum, begonia, cineraria, ferns, forget-me-not, impatiens, ivy, lavender, native violets, primula and periwinkle. The herb rosemary doesn't mind the shade, falls attractively over the edge and provides pretty blue flowers as well as leaves to flavour lamb dishes.

Palmers' Handy Tips leaflet stresses using a premium tub or container mix as these contain water storage crystals, a wetting agent that spreads moisture to the roots, along with slow release fertilisers. Water crystals swell when water is added and act as a water reservoir. The crystals then shrink as the water is taken up by the plant and expand again when the plant is watered.

They advise against using garden soil or compost instead of potting mix in pots as compost generates heat as it breaks down and like soil, it compacts. This starves the plant of oxygen and fertiliser.

Their Tips stress that plants in containers dry out more quickly than plants in the garden. As the plant grows and the root ball becomes denser, it becomes harder for water to penetrate. Early morning or late afternoon is the best time for watering which should be daily in summer. Water thoroughly rather than giving several light sprinkles. Container plants still need watering after light rain.

Geraniums and pelargoniums, whether standard or ivy-leafed, are also favourites for Bill Ward (of Maggie's Garden Show fame). They flower for 10 months, he says, and colours can range from hot red, orange, and purple to softer hues of pink, white and lavender. He's particularly fond of petunias, perennial or annual.

Bill loves combinations of colours that contrast with each other. Yellow nasturtiums, coupled with upright blue rosemary, for instance. Or hot yellow/orange marigolds with the misty-blue flowers of ageratum; marigolds with blue or white lobelia; mixed nemesia or phlox with red, white or purple salvia; prostrate rosemary with the hardy bay (Laurus nobilis). He likes to use black mondo grass as a foil to colourful flowers or trailing plants like ivy.

When planting the solid types of window boxes, Bill suggests adding a layer of coarse gravel to the base which facilitates drainage and will protect the roots of your plants from being waterlogged.

If using open weave wrought iron types of window boxes you can choose to use individual pots. You may choose to line the window box with bird netting or chicken wire, adding dampened sphagnum moss to give a natural look, then add potting mix to around one third the depth before adding the plants.

Caption: scarlet and white petunias turn a drab little space into a delightful area.

JCD with help from David of California Home and Garden; Palmers How to Grow in Containers leaflet and Bill Ward's book on House Plants, Hanging Baskets and Window Boxes (Hyndman Publishing).

Bay View newsletter 65, May 2015