From our perspective, the answer to your question begins with our fundamental genetics. Most lobelia species commonly grown for indoor enjoyment, such as Lobelia erinus, are technically tender perennials. However, our life strategy is heavily skewed towards that of an annual plant. This means our primary evolutionary goal is to channel all our energy into a single, spectacular season of flowering, setting seed, and thereby ensuring the survival of our genetic line. When brought indoors, you are interrupting this natural cycle by preventing us from completing our mission and dying back. You are, in essence, asking us to extend our performance beyond our typical biological programming.
If you provide us with ideal conditions—which we will detail next—you can expect a prolific blooming period that typically lasts from late spring or early summer for about 2 to 3 months. We will produce a constant cascade of small, intricate flowers in shades of blue, violet, white, or red, depending on our cultivar. This bloom period is not indefinite. It is the culmination of our energy reserves. Once this main flush of flowering is over, we will naturally begin to look tired and leggy as we attempt to set seed. Many gardeners treat us as temporary floral displays for this reason, appreciating our intense beauty for a season and then composting us to make room for new plants.
To maximize our lifespan and blooming potential indoors, you must replicate our preferred conditions as closely as possible. We require very bright, indirect light. A south or east-facing window is ideal. Direct, hot afternoon sun through glass can scorch our delicate foliage, while too little light will make us become leggy and cease flowering. We crave consistently moist, well-draining soil. Our roots are fine and susceptible to rot in soggy conditions, yet we wilt dramatically and perish quickly if allowed to dry out completely. Furthermore, we prefer cooler temperatures. An indoor environment of 60-70°F (15-21°C) is perfect. Hot, dry air from heating vents will stress us, shorten our bloom time, and make us more vulnerable to pests like spider mites.
It is possible, though challenging, to coax us into living for more than one year. After our initial major bloom fades, you can give us a "hard haircut." Prune us back by one-half to two-thirds. This drastic measure encourages us to put energy into producing new, bushier growth instead of struggling to support old, spent stems. Place us in a very cool (around 50-55°F / 10-13°C), bright location for a winter dormancy period. Water us sparingly, just enough to keep the soil from turning to dust. In spring, as daylight increases, bring us back to warmer temperatures, resume regular watering, and begin fertilizing with a half-strength balanced fertilizer. With this intensive care, you may successfully get a second, though often less vigorous, year of bloom from us.
