Article and photos by Derek Thomas
Roof top gardens can be transformed to elegant outdoor rooms with container plants.
Many urban gardens have a very limited space to grow the plants and vegetables that an avid gardener would like to have. In fact with the recent condo explosion, In the Washington metro area, many gardens are now just a cement patio or balcony. Not many options for gardening right? How wrong you are. The craft of container gardening has come a long way to serving the needs of the most space challenged Washingtonians. If you have an outdoor space with access to water you can now create the lush gardens that you desire with less effort than you imagine.
When deciding on landscaping with containers there are several important things you must consider for achieving success.
Choosing the containers
Think about the space. Is it in full sun, or dank shade? Are you covering an aspect of your landscape or adding contrast to an existing design? Is the container the focal point or the plants within? Will you want to change the plants seasonally or are you going to install a more permanent planting? Will the area be protected in colder months, or are you going to have to move the containers indoors? Are you container gardening for the beauty of the craft or the functionality of it?
By considering these questions you will be able to make choices about what your containers will be. For instance if you are using containers to plant your vegetables a visit to a full service nursery will provide you with used growers containers. I use the black plastic, 20-gallon size, for vegetables and have had great success with them. You will also save money on these planters since many nurseries will give you their used containers or sell them to you for a greatly reduced cost. However, if your purpose is to add impact to your front entry choosing two cast iron planters filled with palms will give you the impact and elegance you desire. Perhaps your plan is to use the pot as an art object then a concrete urn placed in the shade of your favorite tree will give great contrast and in this instance you have used the planter as an element of design in you garden. If you want to use the planter to add color to your landscape then you can choose one of the high gloss ceramic planters that are now available in many patterns and colors. Just plan to bring these containers in during the winter or house them in an area where they will stay dry, (freezing and thawing tends to crack these type of planters). Since there are so many planters available today doing a little planning before shopping will help you make a smart choice about the containers you choose and where you will use them.
Consider the soil
There are many “container soil mixes” available today. However when choosing one I prefer and have had more success with the ones that are soil-less. These blends are usually identified as potting mixes or container mixes. They will not have the word soil in the label description or name. These potting mixes tend to be lighter and aid in good air circulation in the container. You should never use soil dug from you garden, no matter how good it is, since this soil will compact over time and provide a greatly reduced air circulation to the roots of your plants. You can mix your own container mixes when doing this use ½ peat, ¼ sand, perlite and charcoal (in equal parts totaling about 1/8 of the total mixture), and1/4 organic material (a commercial leaf mold/compost is good for this). You can also add a silicate gel that is sold as an additive to help moisture retention. Follow the instructions on the package since these crystals expand 10 times their size when water is added.
When it comes to filling your containers the choices are as extensive as the containers themselves. Use common sense, plants that perform well in the garden with little care will need more care when grown in a container. Plants that are extremely aggressive may over power their containers. Plants that are extremely delicate may not be suited to the extremes that can be encountered when container gardening.
If you are planting evergreens remember they will need the same seasonal care as if planted in the earth. Evergreens will also require more care as time goes by, you will have to amend the soil and prune regularly. You will need to repot or root prune every couple of years to keep evergreens healthy.
If you are planning to plant tropicals, are you going to bring them indoors in the fall or treat them as disposable? Many tropicals that are kept outdoors in the summer months can become the host of insects. If you have indoor plants and choose to bring in the tropical plants grown outdoors in summer you should consider several sprayings of an organic insecticide prior to bringing them indoors. This will prevent insect spread to you indoor plant collection.
Perennials can be a hit in container landscaping, choose plants that flower for extended periods to give a longer lasting impact. Perennials will perform well for several years in container gardens. After two to three years you can divide them or plant them in the garden and replace them with younger plants.
Once you choose the plant or plants for your container consider a multi plant approach. You can also mix things up, use a tall plant for the impact and combine it with several contrasting plants. Make sure all the plants that you choose in your blend are compatible. Mixing a sun loving plant with three shade plants will not work and depending on placement something in your design will not be happy. You can use grasses, shrubs, and even a variety of trees in your containers. If unsure what to use consult your garden center pro or landscaper for advice. There are many books on the market that either are about container garden plants or have a section dedicated to container plants. Be playful and a focus on what your desired result is for this particular container garden.
This is the most important thing to consider in container gardens. Many times the failure you have experienced is due to improper watering. Your plants will have a better chance of surviving if you took the time to do several water smart things. First make sure that the containers that you use are large enough to accommodate the mature size of the plants. If you are watering your containers and one hour later the plants are wilting then the roots are most likely overcrowded. Planting in large enough pots and not overcrowding to begin with can help to prevent this problem. Always water thoroughly and use a 2”-3” layer of mulch to help water retention. Add a silicate gel to the potting medium. These products are available at most garden centers and work by absorbing water and releasing it when surrounding soil has dried. You can also purchase or have installed a drip irrigation system that works on a timer and provides water at predetermined intervals. When planning your summer vacation work with your neighbors to do a buddy system for watering or move the containers to a shaded location for the time you are away.
Perhaps the most important thing to remember in container gardening is to have fun with this. Don’t be afraid to experiment. Play with colors textures and shapes. Enjoy.
Derek Thomas is principal of Thomas Landscapes. His garden designs have been featured on HGTV’s Curb Appeal, and Get It Sold. His weekly garden segment can be seen on WTTG/Fox 5 in Washington. He can be reached at “http://www.thomaslandscapes.com” or 301.642.5182. Follow us on twitter @thomasgardenguy friend us on Facebook at Facebook/Thomas Landscapes.