Moving indoor or container ferns outside for the summer provides these plants with increased humidity and space for robust growth. Outdoor conditions, including brighter light and better air circulation, often lead to fuller, healthier fronds compared to indoor environments. Since most popular container ferns are tropical or subtropical, their successful move depends entirely on timing the shift to align with consistently warm weather. This careful timing ensures the ferns can thrive without experiencing a cold shock that could damage their delicate foliage.
Identifying Safe Outdoor Temperatures
The most important factor for moving tropical ferns outside is the overnight temperature. These plants are highly sensitive to cold and cannot tolerate frost, meaning all danger of the last spring frost must be completely over before the move. The minimum safe nighttime temperature for most common houseplant ferns, such as the Boston fern, is 50°F. A consistent overnight low of 55°F is a safer benchmark to ensure ongoing healthy growth. Waiting until the weather stabilizes above this 55°F threshold prevents the chilling injury that can cause fronds to turn yellow or stunt new growth.
Acclimating Ferns to Outdoor Conditions
Once the weather is reliably warm, ferns must undergo a process called “hardening off” to transition from the stable indoor environment to the variable outdoor elements. Indoor ferns are not conditioned to handle the intensity of direct sun, wind, or fluctuating temperatures, and sudden exposure will result in severe leaf burn or shock. This acclimatization process typically takes between seven and fourteen days to complete successfully.
Begin the hardening-off period by placing the fern in a deeply shaded, sheltered location for a short duration, such as one to two hours in the late afternoon. The initial sheltered spot should be protected from direct sun and strong breezes, which can quickly dry out the fronds and soil. Each day, gradually increase the amount of time the fern spends outside, moving it slightly closer to its intended permanent location.
This slow introduction to the outdoors minimizes the risk of transplant shock, which can manifest as scorched, crispy fronds. Keep the soil consistently moist throughout this period, as the increased air circulation outdoors causes container soil to dry out much faster than it does indoors.
Choosing the Optimal Outdoor Placement
After the hardening-off period is complete, the permanent outdoor placement must mimic the fern’s native forest floor habitat to ensure continued vigor. The primary requirement for nearly all tropical ferns is deep, consistent shade or dappled sunlight. Direct afternoon sun must be avoided, as the intense light will quickly scorch the delicate fronds.
Ideal locations include areas under the canopy of large trees, which filter the light, or on a porch or patio that faces north or east. Ferns thrive in high-humidity environments, so grouping them with other plants or placing them near a water feature can help create a beneficial microclimate. The location should also offer protection from strong winds, which can rapidly dehydrate the fronds.
Seasonal Maintenance and Re-entry
Outdoor container ferns require diligent attention to watering throughout the warmer months because pots, especially hanging baskets, dry out quickly in the summer heat and wind. Check the soil daily, and water thoroughly when the top inch feels dry, ensuring the pot has excellent drainage to prevent root rot. This frequent watering schedule may mean providing water once or even twice a day during particularly hot or dry spells.
While the fern is outside, inspect the foliage regularly for garden pests. Before the end of the season, a final transition back indoors is necessary to protect the plant from the cold. The optimal time to bring ferns inside is when the nighttime temperatures are consistently forecasted to drop below 50°F.
Moving the fern indoors before the first frost is necessary, as freezing temperatures will kill the plant. Before bringing the plant back inside, fully saturate the foliage with water to dislodge any insects, and inspect the soil closely for unwanted hitchhikers like slugs or snails. A light pruning of any dead or damaged fronds prepares the fern for its winter stay, where it will require less water.