Summersweet (Clethra alnifolia) is a slow-growing shrub, making it a decent choice for pots or planters. Because these shrubs can be large when they reach maturity, they may be suitable in containers for only a couple years at a time. Some smaller varieties of Summersweet can stay in containers for a bit longer. The most important aspect of keeping Summersweet in pots and planters is maintaining consistently moist soil. This may mean placing Summersweet in a spot where it is protected from intense afternoon sun in hotter regions.
Planting Summersweet in Pots
Summersweet can be planted into pots and planters in the spring as they begin to break their dormancy. Choose a pot size that will allow the plant about 2 to 3 year of growth, at least 6 inches larger than the current rootball. Choose a pot that has a drainage hole and use high-quality potting soil or potting mix. Plant Summersweet so that the soil is level with the top of the root ball soil level.
Depending on the variety of Summersweet, you can place your pot in full sun to shade. Keep in mind that pots dry out faster than gardens, and a pot in a full-sun spot may be more difficult to keep watered. Certain pots like terracotta and cement are porous, causing the soil to dry out even faster, and should be avoided. High-quality ceramic pots retain moisture and often come in larger sizes to accommodate Summersweet.
Best Soil For Summersweet in Pots
Because Summersweet does not like to dry out, use a high-quality, moisture-retaining potting soil to plant in. With soil, you get what you pay for. Good quality soils will help keep Summersweet happy and healthy, make watering easier, and will provide your plants with nutrients. To aid in moisture retention, add a few inches of mulch onto the top of the soil. Rocks in the bottoms of pots are unnecessary as they make pots heavier and often prevent them from draining properly. Summersweet does best in well-draining soil, so a pot without a drainage hole is not recommended.
Caring For Summersweet in Planters
Slow-growing Summersweet can be used in planters without the risk of it crowding out other plants quickly. When choosing companion plants, make sure they have the same lighting and water needs as Summersweet; choose annuals or perennials that also appreciate moist soil.
Watering Summersweet in Pots
Soil in pots tends to dry out faster than that in the ground. For this reason, it is important to check the moisture in your pots daily, especially for a plant like Summersweet. Keep the soil consistently moist, only allowing the top inch or so to dry in between waterings. Pots that are placed in full sun may need water every day depending on your climate. When watering pots, water until it flows out the bottom of the pot.
Fertilizing Summersweet in Pots
Many potting soils have plenty of fertilizer mixed in to keep Summersweet happy for its first year in a pot. After a year, add slow-release fertilizer around your potted Summersweet in the spring as the leaves start to emerge. Because nutrients leach from pots more quickly than in the garden, you may need to use liquid fertilizer a couple months after planting Summersweet.
If the leaves begin to lose their deep green color and yellow, it could be a sign that they are in need of fertilizer. Take care when choosing a fertilizer, as those high in nitrogen may take away from Summersweet’s bloom. Instead, choose a fertilizer higher in potash or one that is specifically made for flowering plants.
Winter Care For Summersweet in Pots
Depending on the variety, Summersweet is a cold-hardy shrub that can handle deeply cold winters. However, even the most cold-hardy plants are more likely to be damaged when housed in containers. With its roots above ground and exposed to temperature extremes, you may need to bring your potted Summersweet into a garage or basement in the winter, depending on your climate. Keeping them in a dimly lit but still chilly area over winter allows Summersweet to go dormant, improving its next-year blooms.
Moving potted plants into protected areas also prevents the pots from cracking. In colder regions, the water in pots may freeze, but only the top portion may unfreeze on milder days. This leads to roots sitting in water with nowhere to go, leading to root damage and possible plant death. Be sure to water Summersweet over the winter when in pots and prevent them from drying out completely.
Growing Summersweet Indoors
Like most other flowering perennials, Summersweet will bloom best when it is allowed to go dormant or experience a period of cold. It is best to allow Summersweet to go dormant outdoors in a protected area rather than in your home or in a greenhouse. Over the winter, keep Summersweet in a dimly lit area.
Because Summersweet is deciduous, it is likely to lose all its leaves unless you are in a warmer climate, and thus it will not need light to survive. In warmer regions, potted Summersweet can often be left outdoors without the risk of root damage. Keep the soil consistently moist even through the winter.
Author Lynn Gusman - Published 1-13-2023