Humans have employed containers to grow plants for both function and decoration for centuries. Various cultures such as the Egyptians, China, India and the Romans grew many varieties of medicinal and edible plants in containers with the intent of being able to move plants from one location to another. Even the Europeans utilised containers to transport tropical plants such as breadfruit between the pacific islands and the West Indies. These days container plants have become more of a fixed feature in our urban landscapes. Mobility of containers is still a consideration, but their purpose is often to provide a focal point rather than being utilised for mobility of plants.
Modern garden designs employ the use of containers to provide impact as well as functionality. Containers have become an integral part of landscape design and the diversity of containers available can enhance the overall aesthetic and functionality of any landscape. From the contemporary to the whimsical, there are containers that can provide impact and effective utilisation of space to provide scale and dimension without compromising other design considerations.
Technological changes of the modern era have provided us with a range of materials that containers can be constructed from, each with its benefits and potential pitfalls. The use of recycled materials or repurposed materials in container manufacture has resulted in better quality products that are available in a range of colours and styles to suit any landscape. The desire for sustainable products is becoming increasingly more popular and the environmental impact of some products has seen a shift away from their use.
Plastic pots are undoubtedly one of those products that many people are attempting to avoid but their popularity as a short-term installation cannot be overlooked.
Lightweight, cheap and available in a range of profiles, plastic containers will always remain a viable option for the lower end of the market. Plastic containers will become brittle over time, however many products incorporate UV stabilisation to improve their longevity and due to the method of manufacture through injection moulding, often provide better drainage than some of their more expense contemporary counterparts.
Contemporary containers have become increasingly popular in garden design and the range of Glass Fibre Reinforced Concrete (GRC) containers brings all the elements together to provide a product that has strength to weight ratio greater than traditional wet poured concrete. GRC is durable and will stand up to the harshest of environmental conditions. The beauty of GRC is that it can be purchased in a range of profiles and colours and can be customised to suit any landscape situation. GRC products are made by spraying or pouring a mixture of concrete glass fibre into a slurry to which pigments and waterproofing agents are added before being moulded.
Earthenware containers encompass a large variety of clay-based materials in a range of colours, sizes and shapes, which will ultimately determine the price point. Traditional terracotta pots are extremely porous, but can be a disadvantage due to container media drying out prematurely. This can be overcome with treating the inside of terracotta containers with a sealant, but this comes at an additional cost. An alternative product is Fibrecotta, which is a combination of terracotta reinforced with fibreglass and overcomes the previous limitation.
Glazed containers or large ceramic outdoor planters have been glazed and fired to high temperatures making them tough and hardy. The most redeeming factor for glazed containers is the sheer breadth of styles and colours available. The effects can vary including drip, multi-coloured, and crackled finishes. The beauty of glazed containers renders them for use with or without plants within a landscape.
Metal containers are available in a range of profiles and materials that are suitable for a variety of landscape situations. Metal planters are reasonably priced compared to some earthenware or concrete planters. They are comparatively lightweight and come in styles ranging from plain to ornate. Galvanised zinc tubs are probably the least expensive metal planters, while inlaid copper or brass containers can be quite expensive but are extremely attractive.
Corten Steel planting containers continue to enjoy popularity in landscapes and rightly so. Corten planting containers can be customised into a variety of shapes and the high-end products are usually lined with an insulating material to overcome the biggest problem with metal planters, rapid heat build-up. If containers are not properly insulated, overheating can damage plant roots.
Other popular metals in plant containers include powder coated steel, galvanized steel, stainless steel and aluminium. The choice of one product over another will often depend on price point however all design factors should be considered before choosing one product over another.
Plant Container Functions
Any plant container regardless of size must provide a suitable environment to support plant growth. Containers should provide protection from growing media overheating on north and west facing exposures, water drainage control, stability in high winds, ease of watering, and to a lesser extent portability.
Drainage control is probably the single most important consideration for containers. Containers that do not drain correctly may result in plants suffering from root rot. This is particularly problematic in earthenware pots that often do not have adequate drainage holes installed during manufacture. Conversely if water drains too rapidly from containers, plants will suffer water stress and nutrient leaching, which can lead to plant health decline. Finding the balance is not just a matter of choosing a container with adequate drainage holes. For large containers, the installation of a drainage system may be necessary. The inclusion of geotextile materials and drainage boards can overcome some of the problems, however even these measures can lead to repeated blockage. Good drainage starts with selecting the correct growing medium for containers in the first instance.
Get The Mix Right
Selecting a container mix requires local knowledge of the complex relationship between all the competing factors for beneficial plant growth and maintenance. Therefore, it is essential to ensure that you have a reliable source for your growing media. Specialist suppliers should be consulted particularly when installing high end large container installations. There are a number of functions that a growing media serves: to supply the plant with moisture, air, nutrients and stability. For containers, soilless mixes are the superior choice as a growing media. Soilless mixes are lightweight, drain well, hold water and nutrients, are pH stable and generally free of weeds, insects, and diseases and are typically comprised of ingredients such as coarse river sand, perlite, vermiculite, composted bark, recycled organics, and coconut coir. Suppliers can customise a mix suitable for specific installations.
Thrills, Spills and Fills
Growing individual plants in containers may be appropriate in some circumstances but to maximise impact the ‘thrill, spill and fill’ concept should be employed. Choose the star of the planting, the ‘thriller’ – this plant should be one that is bold and appealing, with a bit of height so it can be positioned at the back of the container. Colourful, strappy leafed plants such as Cordylines or Phormiums work well. For the ‘fillers’ choose smaller, rounded plants to fill the majority of the container. The ‘spiller’ plants are the finishing touch. These are trailing plants that tumble over the edge of the container and complete the look. A classic spiller is Dichondra ‘Silver Falls’. For the best results and success, combine plants that have similar growing conditions.
We can develop amazing green spaces through incorporating beautiful containers into the landscape and with so much diversity available it will be hard to contain the excitement.