Container Gardening, Part I
When thinking about plants in containers, do you envision a windowsill filled with philodendron, grape ivy, and other houseplants, or a tub of petunias sitting on a sunny deck? These examples are only the beginning! Using your imagination, conjure an odd, little space around the house; an empty nook in a garden bed; a lonely stairstep; a small balcony or patio; or just the front door. You can start to dream about where a planter, urn, or basket might be just what you need. Whether you are a novice or a recognized “green-thumb,” container gardening offers a plethora of possibilities!
This article discusses the basic guidelines for growing plants in containers outside. Some ideas can be applied to houseplants; however, spring is the ideal time to plan for outdoor spaces. As with planning a special meal or a vacation trip, there are multiple strategies that can be followed. Getting ready can begin with choosing a container and acquiring other supplies, determining the location, and then selecting plants that fit the designated environment. Flowers, herbs, vegetables, and even trees and shrubs can thrive in containers when given care and attention.
Choosing a Container
A conventional pot, a barrel, or a creative “find” from the attic can make the perfect home for your plants. Drainage is a crucial feature. Excess water needs to soak through the soil and out to prevent problems such as root rot. If a container does not have adequate drainage, you may be able to drill or punch holes with a large nail. In addition, the container needs to accommodate root and plant growth and allow for aeration. Thinking ahead about the size and number of plants you choose to grow will contribute to good decisions regarding container dimensions. A small pot (six-inch round or less than one gallon) is a good choice for a single herb or small flower. A larger container (12″ to 18″ round or 5 gallons or more) can accommodate a collection of several plants or a shrub, such as a hibiscus, or a tomato plant.
Selection of a container impacts both garden maintenance and appearance. A wide variety of materials are used for fabrication. These include pottery, clay/terracotta, concrete/cement, stone, peat pots, wood, molded plastic, fiberglass, metal, wire used for baskets, and recycled items, such as boots or carts. The design and construction of a container affects durability, resistance to temperature fluctuation, watering frequency, and mobility. Popular plastic containers are lightweight and available in an array of colors, sizes, and shapes. Double-wall design on plastic pots can help protect against extreme temperatures, while UV-treated polyethylene is color-fade resistant. Wooden planters are appealing for their natural look, portability, and do-it-yourself options. Choosing a lumber variety resistant to decay (such as cedar) and ensuring that the wood has not been treated with harmful preservative chemicals will help ensure product integrity and safety. Pottery, stoneware, and concrete can offer attractive and substantive planting possibilities. Depending on size and construction, the container may be heavy and difficult to move. Cracks in pottery are exacerbated by freezing and thawing, causing ultimate deterioration if left unprotected outside in the winter. If a decorative vessel does not have adequate drainage, address the problem with double potting: put the plant into a smaller second pot with drainage holes and place on top of some gravel inside a larger primary planter. Wire baskets and other creative receptacles may require a liner for planting. For example, enhance a hanging basket lined with a plastic bag by packing damp moss around the inside.
Grow bags, manufactured with thick, breathable fabric, are available in a variety of sizes and depths, depending on the intended use. They can be filled with soil and placed in a container with one large hole or many holes (like a laundry basket) or hung from a wall or railing. Advantages of grow bags are that they are particularly effective in providing plant roots with aeration and drainage. Also, the risk of soil-borne disease and fungus is significantly reduced by using a new or thoroughly cleaned bag for each planting.
Garden suppliers offer an increasing repertoire of self-watering planters. Models vary, but generally water is drawn from a bottom reservoir into the soil by capillary action through small soil columns or rope wicks. Some planters have a mechanism to manage overflow. These planters are particularly useful for balcony gardening, where water supply and drainage may be challenging, and also for travelers or vacationers. Care should be taken to ensure that the soil is not too wet and plants do not show symptoms of overwatering.
With so many choices, selecting a container may seem overwhelming. As a guideline, keep in mind: convenience, cost, and curb-appeal! Consider the questions below and start simple, building on your successes and container collection.
Preparing the Soil
To support plant growth, soil needs to be aerated, maintain a balance of nutrients, and retain moisture without getting soggy. As already emphasized, drainage is key to keeping plants healthy in a container environment. Commercial garden soil is too heavy and dense, thus depriving the plant of needed oxygen. Earth taken directly out of the garden may have some beneficial nutrients from decomposed organic matter, but like bagged garden soil, it may be too dense and could also harbor insects, disease, or weeds.
Potting soil is a modified or soilless medium, that is composed of various materials. These mixes may include sphagnum peat moss, pine bark, perlite, vermiculite, or clean coarse (builder’s) sand. Some products include water-retaining crystals, which might be advantageous in certain situations. Soil mixes are often amended with slow-release fertilizer. Fertilizer-amended potting soil gives plants a boost in the beginning but will not sustain growth throughout the season. If you are growing organically and want to avoid chemical fertilizers, look for mixes with alternatives, such as bone meal, or lime to adjust acidity if needed.
Since so many products are available, consider the specific needs and watering requirements of your container plantings. Perennials, herbs, and annual flowers tend to prefer soils that are well-drained with more perlite, sand, or bark. Tropical plants and foliage thrive with moist, but not soggy conditions, and succeed with more peat and less coarse material. Purchasing a good quality medium allows you to modify composition and texture to suit your flora.
The portability of containers is an asset in any garden. Heavy planters can be adapted with wheels or a trolley. Planters can be shifted to fill in empty spots around the yard or arranged to embellish a family gathering or event. Vegetables craving sun or tender plants seeking shade can be accommodated. You can situate containers to satisfy light requirements, protect from wind, and tackle temperature and moisture variability.
Start by thinking about microclimates or small spaces with slightly differing light, wind, temperature, or humidity than other areas of your neighborhood or even your own property. You can increase the potential of your container garden by taking advantage of a mini-zone that provides added protection, warmth, and more or less sun as needed. For instance, planters positioned next to a building or fence or in a courtyard will benefit from the heat absorbed by the structure and protection from wind. In reviewing the available lighting, southern and western exposures are the sunniest and warmest; however, the sun’s position deviates throughout the year. Satisfying a pot of sun-thirsty plants, such as verbena and heliotrope, may involve two or three moves from May to September. Survey your environment and maximize spaces that offer the best conditions for the plants you select.
After all this careful preparation, it will finally be time to fill those containers with plants. But which plants? Next month, we’ll discuss all the delightful candidates for your container garden.