Rio Dipladenia is a tropical vining plant, typically grown as an annual in cooler climates that experience frost. Since it cannot survive temperatures consistently below 50°F (10°C), overwintering is necessary to preserve the root system for the next growing season. This process involves transitioning the plant into a controlled, semi-dormant state. Successfully overwintering the plant requires specific steps to ensure its survival and vigorous return to bloom the following spring.
Preparing the Plant for Indoor Living
The transition indoors must be timed carefully, ideally when nighttime temperatures begin to consistently dip below 55°F, and well before the first hard frost arrives. Risking cold damage should be avoided, as a sudden freeze can destroy the plant’s above-ground structure. This timing initiates the plant’s rest period, signaling that active growth must cease.
Before moving the plant indoors, a physical reduction in size and a thorough pest inspection are necessary. The vining stems should be pruned back hard, often reduced by up to one-half or down to 12 inches, to make the plant more manageable in its confined winter space. This cut minimizes the foliage that the root system must support during dormancy and helps prevent the plant from becoming leggy indoors.
After pruning, the plant must be treated for pests, which thrive in the warm, dry air of indoor environments and can quickly spread to other houseplants. Use a strong spray of water from a hose to dislodge any insects, particularly spider mites and mealybugs, which are common on outdoor plants. A spray of insecticidal soap or a diluted neem oil solution should be applied to all leaf and stem surfaces before the plant is moved inside.
Setting Up the Indoor Environment
The indoor location for the Rio Dipladenia must support a cool, resting state without allowing the plant to freeze. The ideal overwintering temperature should remain above 50°F (10°C), but cooler than a typical heated living space, as this helps induce the necessary semi-dormancy. Unheated spaces like a cool basement, spare room, or attached garage that stays above freezing are often suitable locations for this period.
Light requirements depend on the chosen temperature and desired level of dormancy. If the plant is kept cool, it can be maintained in a state of deep rest, requiring only minimal, indirect light or even semi-darkness. If the indoor temperature is warmer, closer to 60-70°F (15-21°C), the plant will remain more active. In this case, it requires bright, indirect light, such as a south- or west-facing window, or under a supplemental grow light.
In a bright location, the plant will likely retain most of its leaves and may continue to grow slowly, though flowering will be minimal. A cooler, darker location will often cause the plant to drop most or all of its foliage. This leaf drop is a natural process of deep dormancy and is not a cause for concern.
Winter Maintenance Schedule
The most significant adjustment is the reduction in the watering schedule, aligning moisture supply with the plant’s slowed metabolic functions. The plant should be allowed to dry out almost completely, and water should only be applied when the top two inches of soil feel dry to the touch. In a cool, dormant location, this may mean watering as infrequently as once per month, just enough to prevent the root ball from shriveling.
During this resting period, the plant requires no nutritional support, so all fertilization must be halted from late fall through early spring. Applying fertilizer will only promote weak, etiolated growth that drains the plant’s limited winter energy stores and will likely not survive. The energy the plant conserves by not producing new leaves or flowers is instead directed toward maintaining the health of the root system and its water-storing tubers.
Even after the pre-move treatment, continuous monitoring for pests remains a necessary chore throughout the winter. The dry air in most heated homes creates an environment where indoor pests like spider mites can reproduce rapidly, so a weekly visual inspection of the leaves and stems is prudent. While the plant is tropical, the low humidity of an indoor winter environment is tolerated, and excessive misting can potentially encourage fungal issues when combined with reduced light and cool temperatures.