Boston Fern Care Outdoors in Winter: A Complete Guide

Boston ferns are a popular variety of fern grown both indoors and outdoors. With their gracefully arching fronds, these plants add lovely greenery and texture to gardens and patios during the warm months. However, caring for Boston ferns outdoors through the winter can be challenging, especially in colder climates.

This article provides a complete guide to outdoor Boston fern care in winter You’ll learn tips for preparing ferns for colder weather, overwintering methods, proper watering techniques, and ways to protect plants from frost, wind, and other hazards. Follow these best practices and you can increase the odds of your outdoor Boston ferns surviving the winter in great shape.

An Overview of Boston Ferns

Native to tropical regions, Boston ferns (Nephrolepis exaltata) thrive in warm, humid environments. Under ideal growing conditions, these ferns can reach lengths of 4-5 feet. The lacy, arching fronds create a graceful, cascading appearance as they spill over containers and garden beds.

Since they originate in subtropical areas, Boston ferns can only withstand mild winters. They are hardy outdoors in USDA zones 8-11 where winter temps rarely dip below freezing. Any colder and they will require overwintering indoors or in a protected structure. Even in warm zones they need some protection from winter extremes.

Preparing Outdoor Boston Ferns for Winter

If you want to maintain your Boston ferns outdoors all winter, take these key steps in early fall to prep them for dormancy:

• Prune off any dead, damaged, or yellowing fronds so the plant can direct energy into the healthy foliage. Avoid major pruning late in fall.

• Apply a slow-release fertilizer in early fall to provide nutrients through the winter months.

• Water ferns deeply before the first frost. Well hydrated plants better tolerate cold damage.

• Add a 4-6 inch layer of insulating mulch like pine straw or leaves around the base.

• Position ferns near heat sources like south-facing walls or under tree canopies for subtle warmth.

• Use portable heaters or frost blankets when extreme cold threatens.

• Monitor weather and adjust care as needed all winter long.

Ideal Winter Conditions for Outdoor Boston Ferns

Even in warm winter climates, Boston ferns need consistent moisture and protection from temperature swings:

Temperatures: Ideal temps are 60-80°F. Brief light frosts in the low 30s°F are tolerated if sheltered.

Light: Bright, indirect winter light is best. Reduce water slightly in very sunny spots.

Water: Water 1-2 times per month in winter, enough to moisten soil. Avoid overwatering.

Humidity: Mist ferns and use humidity trays. Humidity is crucial.

Carefully maintain these preferred conditions throughout winter for best results.

Winter Care Dangers to Avoid

While Boston ferns are resilient, there are some key threats to avoid:

• Freezing temps – Even brief freezes can damage fronds. Cover ferns at first frost.

• Winter winds – Desiccating winds dry out foliage. Use sheltered locations.

• Overwatering – Excess winter moisture causes root rot. Allow soil to partially dry between waterings.

• Low humidity – Dry winter air dehydrates fronds. Provide ample humidity.

• Sun scalding – Harsh winter sun can burn fronds. Filter sunlight as needed.

• Heavy snow – Weight of snow crushes fronds. Carefully shake off snow before it compacts.

Adjust care as required to defend against these hazards and keep ferns healthy.

Providing Winter Water for Outdoor Boston Ferns

Proper watering is critical for outdoor Boston fern winter care. While the plants need moisture, overwatering causes major issues:

• Water less frequently, only when the top few inches of soil become dry.

• When watering, soak the soil thoroughly until excess drains from the bottom.

• Always dump out water collecting in saucer trays so ferns don’t sit in excess moisture.

• Mist plant fronds periodically to boost humidity.

• Use rainwater or melted snow instead of treated tap water when possible.

• Partially sink pots in the ground to help retain soil moisture longer.

Adjust watering to match winter’s slower growth, avoiding constantly soggy soil.

Protecting Outdoor Ferns from Winter Elements

Outdoor Boston ferns need ample protection from harsh winter conditions. Here are some effective options:

• Cold frames – Mini greenhouse structures maintain warmer temps and humidity.

• Cloches – Bell jars trap warmth but allow airflow. Ventilate on sunny days.

• Frost blankets – Breathable fabric provides 4-8 degrees of cold protection when fastened tightly.

• Burlap wraps – Wrap burlap around ferns and stakes to insulate from wind and frost.

• Mulch – A thick mulch layer keeps roots warmer and moist.

• Tree canopy – Situate ferns where leafless branches provide shelter.

• South walls – Brick or stucco walls radiate subtle daytime warmth.

Choose solutions fitting your climate and exposure. Combining methods offers the best protection.

Overwintering Indoors

In climates colder than USDA zone 8, overwintering Boston ferns indoors is recommended. Ideally, bring them inside a few weeks before your first average fall frost date. Here are tips for overwintering indoors:

• Prune back long fronds by several inches before bringing inside to fit the space.

• Select a bright room with east or south-facing windows for winter sunlight.

• Water slightly less, allowing the soil to partially dry between waterings.

• Provide a humidifier or pebble tray for essential air moisture.

• Maintain indoor temperatures between 60-70°F. Avoid drafty areas.

• Move to lower light if fronds yellow. Watch for signs of sunburn.

• Return ferns outside after the last spring frost once nights exceed 50°F.

With proper winter protection, Boston ferns can survive outdoors even in cooler climates. Pay close attention to their needs, and you’ll be rewarded with their graceful beauty in your garden year-round.

Frequently Asked Questions

Can Boston ferns stay outdoors all winter?

In frost-free climates (zones 8-11), Boston ferns can stay outdoors year-round with proper care. Any colder, and they will need winter protection or overwintering indoors.

What is the ideal temperature range for outdoor Boston ferns in winter?

The ideal temperature range is 60-80°F. Brief light frosts in the low 30s are tolerated if plants are protected. Avoid prolonged freezes below 32°F.

How often should I water outdoor Boston ferns in winter?

Water outdoor ferns every 1-2 weeks in winter, when the top few inches of soil become dry. Provide enough water to moisten the soil but avoid keeping it soggy.

Should I fertilize my outdoor Boston ferns in winter?

Avoid fertilizing dormant outdoor Boston ferns in winter. If you did not provide slow-release fertilizer in fall, resume regular feeding in spring after new growth emerges.

What can I use to protect my outdoor ferns from winter cold?

Use protective solutions like cold frames, burlap wraps, frost blankets, tree canopies, and south-facing walls. Combining multiple methods provides the best winter protection.

How do I know if my outdoor Boston fern needs overwintering indoors?

If you live where temps regularly fall below freezing (USDA zones 7 and colder), Boston ferns will need to be overwintered indoors. Bring them in before the first expected fall frost.

When should I move outdoor Boston ferns back outside in spring?

Once spring nighttime temperatures reliably remain above 50°F and the threat of frost has passed, you can begin transitioning Boston ferns back outdoors.