You can absolutely put perennials in pots, a practice that offers gardeners immense flexibility and portability. Perennials live for more than two years, returning season after season. Using them in containers allows you to transform small spaces like patios and balconies, or to easily rearrange plants. This method also gives you precise control over the soil type and growing conditions, which is helpful for plants with specific needs.
Choosing Suitable Perennials and Containers
Successful container perennial gardening begins with careful selection of the plant and its vessel for long-term health. When selecting perennials, choose varieties that are rated for hardiness zones one to two zones colder than your local climate. This extra margin of cold tolerance is important because roots in a pot lack the ground’s insulation and are more exposed to temperature extremes. Perennials with fibrous root systems, such as Hostas, Sedums, and many ornamental grasses, generally adapt well to the confined space of a container.
The container itself plays a major role, and generally, a larger size is better because a greater volume of soil provides more insulation and root space. Container material affects how quickly the soil dries out; porous materials like unglazed terracotta allow moisture to evaporate rapidly, requiring more frequent watering. Glazed ceramic or plastic pots retain moisture more effectively, but regardless of material, every container must have adequate drainage holes to prevent waterlogging and root rot.
A high-quality, lightweight potting mix is necessary, as garden soil compacts too easily and restricts drainage and air exchange. This specialized mix typically contains components like peat moss, coir, or pine bark, combined with perlite or vermiculite for moisture retention and proper aeration.
Active Season Care and Soil Management
Potted perennials require a different maintenance approach than their in-ground counterparts, particularly concerning water and nutrients during the active growing season. Containers dry out significantly faster than garden beds, sometimes needing water daily during hot or windy weather. Check the moisture level by inserting a finger an inch or two into the soil; if it feels dry, water until it flows freely from the drainage holes.
Frequent watering constantly leaches nutrients from the soil, leading to depletion faster than in the garden. To compensate, incorporate a slow-release granular fertilizer into the potting mix at the beginning of the season or use a diluted liquid fertilizer every few weeks. This consistent feeding ensures the plant has the necessary elements for healthy foliage and flower production.
Over time, perennials can become root-bound, where roots densely circle the inside of the container. Signs include roots emerging from drainage holes, water running straight through the pot, or stunted growth. Repotting or dividing the perennial is necessary every two to three years to maintain vigor. When repotting, select a container only one to two inches wider than the old one, gently loosen the tangled roots, and refresh the potting mix.
Preparing Container Perennials for Dormancy
The most challenging aspect of growing perennials in pots is protecting them during the winter, as the roots are highly vulnerable to freezing temperatures. Unlike in-ground plants, where the surrounding earth insulates the roots, a container exposes the root ball to cold air on all sides. This lack of insulation means the soil temperature can quickly drop to the ambient air temperature, potentially killing the roots even if the plant is rated as hardy.
To maximize survival, choose plants that are two zones hardier than your region, or implement methods to insulate the pots once the plant has entered dormancy after the first hard frost. One effective strategy is to group the pots closely together against a sheltered wall, which creates a microclimate and protects them from harsh winds. For smaller containers, you can bury the entire pot in the ground, allowing the surrounding earth to provide natural insulation.
Alternatively, insulate the pots above ground by wrapping them in materials like bubble wrap or burlap, or by building a cage and filling the space with straw or shredded leaves. Moving dormant perennials into an unheated garage, cold frame, or shed provides excellent protection while still allowing the necessary chilling period. Even during dormancy, the plants need occasional, minimal watering to prevent the root ball from completely drying out, a condition known as desiccation.