A penthouse garden towering high above the skyline of a major metropolitan city is the equivalent of Eden for those of you who are garden lovers trapped in the big city. It's a tranquil oasis and retreat from the hustle and bustle down below, and the contrast vividly sharpens the appreciation. But, creating a area like this is a challenge.
When it comes to roof-top potted patio gardens, you will have specific challenges. Space is a premium, building codes for weight and materials must be adhered to and the rooftop climate swings can create extremes. Obviously all the plants you want to use must be contained in some sort of planter. As with any garden even ones you a back yard there will be special problems and opportunities.
Limited Space: A postage size potted garden serves as a outdoor room for summer living and entertaining. You want to create the appearance of lushness without crowding out people so planters that take up a minimum of space is perfect. We like the tall, slender ones show that can hold a tall, narrow tree to create maximum impact in a vertical space.
They need to be big to hold enough soil for the size of tree you want to plant to develop a healthy and hardy root system. When you crowd the containers together the foliage mass create a natural living barrier for privacy and to block unsightly other buildings. Make sure if you are working in a load limitation that the trees, pots and soil are all in that range.
Weather is exaggerated on a rooftop. It gets colder and hotter than on the ground levels below. It's good to have at least half a day's shade to moderate the summer heat. Moisture supply can be another problem on a rooftop.
Rain that soaks into ground level soil is always available but on a rooftop most of the rainfall runs off. The amount that soaks into a garden planter is much less than would be available to plants growing in the ground. In addition, the drying effect of extreme temps and winds is a real threat to the potted plants.
They bake in summer and freeze in winter. The solution is a watering systems. It reduces the stress on plants and relieves the home owner of this chore. In the winter you can turn it off so the water doesn't freeze in thepots and crack them.
There are certain types of plant materials to consider when selecting them for your planters. Conifers are ideal because they provide a variety of foliage colors and textures, are interesting to look at and tolerate extreme heat, cold and winds. In late spring you can plant a few colorful annuals like impatients and salvias. They tolerate being crowed into planters without succumbing to fungal problems. Perennials don't tend to fare well, as they are too vulnerable to cold temps.
Obviously ground level rules don't apply of a rooftop. Most important is selecting plants that are slow growing, tolerate crowding, and hard most of the year. But, of course don't forget.....they have to fit into the elevator first!