When to Plant Begonias Outside: A Guide to Maximizing Their Beauty

Begonias are some of the most popular flowering plants grown in gardens thanks to their showy blooms and attractive foliage. But knowing when to transplant these beauties from indoors to the garden is key to helping them thrive. In this article, we’ll explore the ideal time to plant begonias outside based on the climate and growing conditions in your area.

With over 1,800 species, begonias are native to tropical and subtropical regions across the world. They come in a diverse range of sizes, leaf shapes, and flower colors. Begonias are broadly categorized into the following types:

• Tuberous begonias – Grown for their large, showy blooms that come in bright shades like pink, red, orange, yellow, and white. They grow from tubers and are often treated as annuals

• Wax begonias – Also called fibrous-rooted begonias. They have smaller flowers but are prolific bloomers. Wax begonias work great in garden beds and container plantings.

• Hardy begonias – A small group of begonias like the popular Begonia grandis that can withstand colder climates and overwinter outside in sheltered locations

• Foliage begonias – Prized for their spectacular ornamental leaves. Rex begonias and cane begonias fall in this group. They make excellent houseplants.

When to Move Begonias Outdoors

Begonias thrive in warm weather and quickly suffer damage if exposed to frost or freezing temperatures. Planting begonias outside requires waiting until the danger of frost has definitively passed.

In general, begonias can be moved outdoors about 1-2 weeks after your region’s average last spring frost date. But it’s also important to watch the weather forecast specifically for freezing temperatures before transplanting. Some tips:

• In USDA zones 8-10 where winters are mild, begonias can be planted out as early as February or March.

• In colder zones like zone 5 and 6, wait until early May to plant begonias after you’re confident the last frost has passed.

• In zone 3 and 4, transplant begonias in late May when nighttime temperatures remain above 50°F.

• Don’t rely solely on the zone hardiness map. Track your local weather and only plant begonias after several consecutive days of temperatures above 40°F.

• Be ready to protect newly transplanted begonias with cloches or fabric row covers if an unseasonal frost threatens your area in early spring after planting.

Preparing Begonias for Transplanting Outdoors

To ensure begonias transition smoothly from indoor conditions to the garden, they need a period of “hardening off”. This toughens up the plants before exposure to direct sun, wind, and other elements.

Here are some tips for hardening off:

• Start the process 1-2 weeks before the last expected frost.

• Move pots outdoors into partial shade for a few hours, bringing them back indoors for the night.

• Gradually increase the time spent outside over 7-10 days.

• Introduce to direct sunlight for just 1-2 hours on the last few days.

• Avoid hardening off on extremely hot, cold, or windy days.

• Reduce watering during the hardening off period but don’t let plants severely wilt.

• Plant outdoors only after 7-10 days of gradual hardening off.

Choosing the Best Outdoor Location

When selecting where to plant your begonias, keep these factors in mind:

Sunlight

• Most begonias flourish in partial shade or dappled sunlight.

• Variegated foliage begonias appreciate some early morning sun to bring out leaf colors.

• Cane begonias and a few other sun-loving varieties can tolerate a few hours of direct sun but need afternoon shade.

Soil conditions

• Begonias thrive in organically rich, slightly acidic, well-draining soil. Add compost prior to planting if needed.

• Improve drainage in heavy, clay-like soils by mixing in materials like peat moss.

• Test soil pH and amend with sulfur to lower if too alkaline.

Air circulation

• Allow for good air movement to prevent fungal diseases. Space plants adequately.

• Avoid planting in enclosed, humid locations like against walls or under eaves.

Shelter

• Protect from strong winds that can damage delicate stems and foliage.

• Site them near fencing, shrubs or other structures that provide windbreaks.

Planting Begonias in the Garden

When planting begonias in beds or borders:

• Dig holes the same depth as the rootball and 2-3 times as wide.

• Gently loosen the roots if rootbound and place in the hole.

• Backfill with native soil, pressing firmly around roots to remove air pockets.

• Water thoroughly after planting to help settle the soil.

• Space begonias 6-12 inches apart depending on their mature size.

Caring for Outdoor Begonias

To keep your begonias looking their best in the garden:

• Water whenever the top 1 inch of soil becomes dry. Avoid wetting foliage at night.

• Apply a balanced, water-soluble fertilizer every 2-3 weeks during the active growth period.

• Remove spent flowers and dying foliage to encourage new blooms.

• Stake taller varieties if needed to prevent damage from wind and rain.

• Watch for slugs, snails and other pests. Remove by hand or use iron phosphate baits if infestations occur.

• In cold climates, transplant back indoors before the first fall frost, typically around late September or October.

Overwintering Begonias

While most types of begonias are not cold hardy, there are a few strategies gardeners in cooler regions can use to save their plants from year to year:

• Dig up tuberous begonia tubers after the foliage dies back in fall. Store them in a cool, dry spot over winter before replanting in spring.

• Take cuttings from wax and other begonias to propagate new plants indoors during winter under grow lights.

• Bring potted begonias indoors to a sunny window before frost. Reduce watering and limit fertilizer until spring.

• In zones 8-10, hardy begonias like the rhizomatous Begonia grandis can be left in the ground over winter if thoroughly mulched.

Key Takeaways

Knowing when the time is right to move your begonias from indoor comfort to the great outdoors is critical for their health. Follow these best practices:

• Wait until after the average last spring frost and nightly lows are above 50°F before transplanting outside.

• Harden off begonias gradually over 7-10 days to avoid shock from outdoor conditions.

• Plant in an area with organically rich soil, partial sun exposure, and protection from wind.

• Provide regular water and fertilizer during the growing season. Move containers and non-hardy plants back indoors before fall frost.

With the proper advance planning and care, your begonias will reward you with their dazzling flowers and foliage all season long. Just be patient and avoid setting them outside too early before the weather has stabilized.