Greetings. I am Lobelia siphilitica, often known as Great Blue Lobelia. While my natural preference is for the moist, rich soil of a stream bank or woodland edge, I can indeed thrive in a container if my specific needs are met. Here is what you must understand from my perspective to ensure my success.
My roots require a home that provides both room to grow and consistent moisture without becoming waterlogged. Choose a container that is at least 12-16 inches deep and wide. This gives my root system ample space to establish itself. The most critical factor is drainage; the pot must have holes. My roots demand oxygen and will quickly rot in stagnant water. For my foundation, use a high-quality, peat-based potting mix. It should retain moisture well but also be amended with some perlite or vermiculite to ensure it remains open and well-draining. I am a heavy feeder in a confined space, so mixing in a slow-release fertilizer at planting time will provide a steady supply of nutrients throughout my growing season.
This is the most crucial aspect of my container life. I am notoriously thirsty. In the ground, my roots seek out constant moisture. In a pot, I rely entirely on you. You must check my soil daily, especially during hot or windy weather. The goal is to keep the soil consistently damp to the touch, like a well-wrung-out sponge. I will wilt dramatically if I am too dry, and while I may recover with a thorough watering, repeated stress will weaken me and shorten my display. However, I equally despise sitting in a saucer of water. Empty the drainage saucer after watering to prevent my roots from suffocating and rotting. A layer of mulch on top of the soil, such as fine bark or compost, will help significantly in reducing evaporation and maintaining the moisture levels I crave.
My ideal lighting condition is partial sun. I appreciate the gentle morning sun but need protection from the intense, scorching heat of the afternoon. A spot with dappled sunlight or about 4-6 hours of direct sun is perfect. In full, hot sun, my container soil will dry out too rapidly, and my leaves may scorch. In full shade, I will become leggy and may not flower as prolifically. As a perennial, I am hardy, but my container exposes my roots to freezing temperatures. To help me survive the winter, you must protect my pot. The best method is to move my container to an unheated garage or sheltered location after my foliage dies back in the autumn. Alternatively, you can insulate the pot by burying it in the ground or wrapping it with burlap and mulch.
I am a short-lived perennial. In a container, I may require more frequent division to maintain my vigor. Every 2-3 years, in early spring, gently remove me from my pot and divide my root mass into several sections. Replant the healthiest divisions in fresh potting mix. This reinvigorates me and prevents me from becoming pot-bound. After my main flush of blue flowers fades in late summer, you can deadhead the spent spikes. This often encourages a second, smaller show of blooms. Otherwise, allow some flowers to go to seed if you wish for me to self-sow, though this is less reliable in containers. My vertical spires of blue flowers will attract pollinators like bumblebees and hummingbirds, bringing life and movement to your patio or balcony.
