Using Perennials and Shrubs as Container Plants
When it comes to container gardening there is a big emphasis on getting a quick fix of colour – nurseries are full of bowls of pansies in spring, salvias in summer and mums in fall. Annual flowers in full bloom are an easy way to spruce up your doorstep, but plants with a longer lifespan – shrubs and perennials – are equally worthy of container culture. They bloom year after year and are larger, helping to soften the space of a balcony, deck or patio with vegetation throughout the seasons.
Just like a well-designed yard, a well-designed container garden should have several layers of plants. They may mingle together in one container or each be presented in their own pot, in a grouping of several. Those vibrant annuals are great in the foreground while they are in bloom, but a few choice shrubs, especially evergreen ones, will form a verdant backdrop year round and a carefully curated selection of perennials provides a varying spray of colour and texture in spring, summer and fall in the mid-ground. Consider ferns for shady niches, ornamental grasses for exposed windy locations and succulents on hot south-facing walls.
The right size container for the plant is one of the most important considerations for keeping potted shrubs and perennials in good condition year after year. One gallon containers are fine for perennials in their first year, but most need a five gallon container to stay happy in the long term. For shrubs, five gallon containers suffice at first, but depending on their mature size, 15 gallon size pots or larger will eventually be necessary. Good quality soilless potting mix is important, though it should be refreshed every few years. Applying a balanced slow release fertilizer during the growing season goes a long way toward replacing the nutrients that are leached out of potting soil every time you water.
Matching your container plants to the sun exposure they will receive is the most important selection criteria, but it's also important to match them to each other, just like you would if you were laying out a garden bed. Hostas look great with hydrangeas, for example, but neither would pair well with a yucca plant – the woodsy look and the desert look just don't go together.