Any plant can be successfully grown in a container. In our gardens, I grow a wide range of roses, herbaceous perennials, alpines, water garden plants, evergreens and yes, even annuals in containers.
My garden would be the poorer if it were constrained to the traditional "annual in a bucket" look. I also believe that gardeners who restrict their plant choice to those plants advocated by the horticultural industry as "container plants" cheapen their own gardening experience.
To me, one part of gardening is learning to be adventurous, to be bold with the use of plants in the garden. To grow the plant you like in the place you want to enjoy it is the ultimate plant growing experience.
Growing in containers allows a gardener to enjoy any plant in almost any location.
Because any plant can be grown in a container, this book will not list appropriate plants for container growing.
Instead, the author will simply suggest that if the plant is alive and the reader enjoys the plant - for flower, leaf or fruit - then it is a suitable candidate for container growing.
There are four primary factors to be considered when growing container plants: the container itself, the appropriate soil for the plant, feeding the plant and providing adequate water. Each of these factors is considered below.
The choice of container is as important in the garden as the choice of plant to fill it as it is this initial choice that sets the tone for the rest of the garden adventure.
A pair of old rubber boots can indeed by used to hold geraniums and petunias but this choice of container sends an entirely different design message than using a hot-fired Italian clay pot filled with the same plants.
The first time a tipped-over barrel is filled with flowers to make it appear as if the flowers were spilling out over the lawn, it is cute. An entire street of such barrels resembles a gaudy theme park more than a gardening neighborhood.
The easiest way to decide about personal style is to spend a winter examining the pictures of other container gardens in magazines and books.
Keep a record of the containers that particularly appeal to your gardening sense of style and copy those designs and pots in your own garden. Imitation is the sincerest form of flattery.
Clay pots are the best pots for growing plants. I say this after 20 years in the nursery business and 20 years of growing a wide variety of plants in every kind of container in the industry.
To be sure, clay has its drawbacks but its ability to support plant life is not one of them. Clay is heavy, it breaks if dropped and is more expensive than plastic. These are the drawbacks to clay cited by other gardeners but these are more than compensated in my mind by the superior growth conditions clay provides.
I was delighted when I obtained Mr. Julius Heinrich's 1911 book on container gardening and found he shared my opinion. In a discussion of pots he wrote, "After years of trial and experience, I find that the best pots in which to grow plants are the common clay pots."
Clay pots breathe. Moisture moves through the sidewalls as well as downward through the soil. This moisture on the side walls evaporates during hot summer days providing a potential cooling effect to the soil and plant roots that is not duplicated in plastic pots.
Clay is heavier than other pot materials but this is to its advantage during summer windstorms. It does not tip over as readily, leaving crushed plants and ruined blossoms scattered in its wake. I like the solidity that clay brings to the garden and I confess that while the look of clay has been duplicated in plastic pots, the ability to breathe has not.
Clay, unlike plastic, will not break down in sunlight and can, with careful handling, last for many years in the garden.
If clay pots are going to be used, purchase the high or hot-fired clay. These will not spall, flaking off pieces of their sides, in the garden during the winter months.
I have some of these good pots in my garden that are twenty years old while the cheaper clay pots only last a few years before they must be tossed into the local landfill. The more expensive high temperature fired pots can even be left outside (although I do not recommend it - it has happened) over the winter in our zone 4 garden without damage.
As a nurseryman, I have grown more plants in plastic pots than any other kind and they do have advantages. All forms of plastic pots on the market hold water better than similarly sized clay pots. This is one reason the nursery trade uses plastic: a plant growing in a plastic pot will require less frequent waterings than one grown in clay.
The plastic does not sweat -or cool down the plant - through the sidewalls. The second reason the nursery trade moved to plastic was that it was significantly lighter than clay. If a plant has to be moved about, a light plastic pot makes the task that much easier.
Plastic is also cheaper than clay and this can be a significant difference when more than a few pots are to be used.
Plastic does not break as easily as clay but it does break down in the sunlight and after a few years, cheap plastic pots become so much plastic dust in the garden.
Both the large clay and plastic pots can have their drainage hole sealed to make them watertight.
I use a hot glue gun for this purpose and then use the water-holding pots for growing my water lilies and bog plants.
Wooden tubs or window boxes also grow a good plant. In our area, the whiskey barrel is the preferred container for dockside planting. It is heavy enough that it is not blown around and "borrowed" by passers-by. It is large enough that it survives a week or more without constant watering and it looks good when painted and maintained. There are even liners available in garden centers now that will turn these half barrels into small water gardens.
Many friends or customers have complained about their window boxes rotting after a few years of gardening. There are two methods to retard this rotting that have worked well in my garden. The first and preferred solution is to have a liner for the window box.
A metal liner is the optimum and deluxe solution but -never seeming able to afford such luxury - we made our wooden boxes the right size so that the paper-fiber boxes available at garden centers would drop right inside.
Two fiber window boxes dropped into our wooden liner, and the wooden-box look is complete without the problem of rotting wood
Mr. Heinrich also suggested simply placing the potted plants into the wooden boxes - without using soil in the wooden box. If peat moss is packed around the potted plants to help hold them upright and act as a moisture reserve, the plants will thrive for the summer. This is an excellent technique for summering houseplants outdoors.
For many years, I have held many of my greenhouse stock plants in large containers constructed of railroad ties and packed with wet peat. While on a somewhat larger scale than the average homeowner would require, the technique is the same and the results, as measured by plant growth and summer bloom, are excellent. The plants grow well all summer, and in the fall are quite content to move back indoors.
Concrete tubs and the newer foam pots act very much like plastic pots in the way they grow plants. The obvious advantage of the foam pots is their extreme lack of weight - making them easy to move about in the garden. If you are the kind of gardener who moves plants about as you would furniture, this lack of weight may be to your advantage.
Concrete on the other hand, is of a more permanent nature. The foam has not been on the market long enough to evaluate its sunlight degradation qualities but because it is impermeable, it will act exactly like plastic for watering.
Concrete, although it does sweat if kept full of water, acts more like plastic than clay for water holding capacity and if properly made will not degrade in the sunlight.
Author Note: This is an ongoing project to publish the entire Gardening Wisdom (award winning book) online. I usually publish one part of a chapter a week and you can be notified of new additions by signing up for the newsletter from the navigation bar
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