Colorado’s high elevation and cool nights push begonia planting to late May or early June. Knowing the Best Time To Plant Begonia In Colorado is the first step to a thriving garden. This guide covers everything from frost dates to soil prep, so you can enjoy blooms all summer.
Begonias are tender perennials that hate cold. In Colorado, the last frost can sneak up as late as mid-May in some areas. Planting too early means risking your plants to a freeze. Wait until the soil warms and nights stay above 50°F.
Best Time To Plant Begonia In Colorado
The ideal window for planting begonias in Colorado is from late May to early June. This timing avoids the common late-spring frosts. It also gives the soil enough time to warm up, which begonias need to grow strong roots.
If you live in the Front Range, like Denver or Boulder, aim for the last week of May. In higher elevations, such as Colorado Springs or the mountains, wait until mid-June. Lower elevations on the Eastern Plains can start a bit earlier, around mid-May.
Why Timing Matters So Much
Begonias are native to tropical and subtropical regions. They cannot handle frost at all. Even a light frost will turn their leaves black and mushy. Colorado’s unpredictable spring weather makes timing critical.
Soil temperature is just as important as air temperature. Begonias need soil that is at least 60°F. Cold, wet soil can cause root rot. Using a soil thermometer takes the guesswork out of planting.
Checking Your Local Frost Dates
Your exact location in Colorado changes the planting date. Use these general guidelines:
- Denver metro area: Last frost around May 5-10. Plant begonias after May 20.
- Colorado Springs: Last frost around May 10-15. Plant after May 25.
- Fort Collins: Last frost around May 5-10. Plant after May 20.
- Mountain towns (like Leadville): Last frost as late as June 10. Plant after June 15.
- Grand Junction: Last frost around April 25. Plant after May 10.
Always check your local extension office for the most accurate dates. Weather patterns shift year to year.
Preparing Your Garden For Begonias
Before you plant, get your soil ready. Begonias like rich, well-draining soil with lots of organic matter. Colorado soil is often clay-heavy or sandy, so amending it is key.
Testing And Amending Soil
Start by testing your soil’s pH. Begonias prefer a slightly acidic pH between 5.5 and 6.5. Most Colorado soil is alkaline, so you may need to lower the pH.
Add compost or peat moss to improve drainage and acidity. Mix in 2-3 inches of organic matter into the top 6-8 inches of soil. This helps roots spread easily.
Choosing The Right Location
Begonias need bright, indirect light. Direct afternoon sun in Colorado can scorch their leaves. Morning sun with afternoon shade works best. If you plant in full shade, they may not bloom as much.
Protect them from strong winds. Colorado’s gusts can dry out plants quickly. A spot near a wall or fence provides shelter.
Planting Begonias Step By Step
Follow these steps for the best results. Whether you are planting tubers or seedlings, the process is similar.
Planting Tuberous Begonias
Tuberous begonias are popular for their large, showy flowers. Start them indoors 8-10 weeks before your last frost date. This gives them a head start.
- Fill a flat or pot with moist potting mix.
- Place the tuber with the concave side up (the indented side).
- Cover with about 1/2 inch of soil.
- Water lightly and keep in a warm spot (70°F).
- Once sprouts appear, move to a bright window.
- Harden off plants by setting them outside for a few hours each day for a week before planting.
- Plant outdoors after the last frost, spacing them 8-12 inches apart.
Planting Seedling Begonias
Nursery seedlings are easier for beginners. Choose healthy plants with dark green leaves and no yellowing.
- Dig a hole twice as wide as the root ball.
- Place the plant at the same depth it was in the pot.
- Backfill with soil and press gently.
- Water thoroughly after planting.
- Add a 2-inch layer of mulch to keep soil cool and moist.
Caring For Begonias Through Colorado’s Summer
Once planted, begonias need consistent care. Colorado’s dry climate and intense sun require attention to watering and feeding.
Watering Needs
Begonias like evenly moist soil but not soggy. Water when the top inch of soil feels dry. In hot weather, this may be every 2-3 days. Water at the base to avoid wetting the leaves, which can cause powdery mildew.
Use a soaker hose or drip irrigation for best results. Avoid overhead sprinklers. Morning watering is ideal so leaves dry by evening.
Fertilizing For Blooms
Feed begonias every 2-4 weeks with a balanced, water-soluble fertilizer. Look for one with equal parts nitrogen, phosphorus, and potassium (like 10-10-10). Too much nitrogen gives leaves but few flowers.
Stop fertilizing in late August to let plants slow down for fall. This helps them store energy for the next season if you overwinter tubers.
Deadheading And Pruning
Remove spent flowers to encourage more blooms. Pinch off dead leaves to keep plants tidy. If begonias get leggy, trim back stems to promote bushier growth.
For tuberous begonias, let the foliage die back naturally in fall. This feeds the tuber for next year.
Common Problems And Solutions
Even with good care, begonias can have issues. Here are the most common in Colorado.
Powdery Mildew
This white, powdery fungus appears on leaves in humid conditions. Colorado’s dry air helps, but poor air circulation can cause it. Space plants properly and water at the base. If it appears, use a fungicide or a baking soda spray (1 teaspoon per quart of water).
Root Rot
Overwatering or heavy clay soil leads to root rot. Symptoms include yellowing leaves and mushy stems. Prevent it by using well-draining soil and letting the top inch dry between waterings. If rot sets in, remove affected plants and improve drainage.
Pests
Aphids and spider mites can attack begonias. Spray them off with a strong jet of water. For severe infestations, use insecticidal soap. Check the undersides of leaves regularly.
Overwintering Begonias In Colorado
Begonias will not survive Colorado’s cold winters outdoors. You have two options: treat them as annuals or save the tubers for next year.
Saving Tuberous Begonias
In fall, before the first frost, dig up the tubers. Cut back the stems to 2-3 inches. Let the tubers dry in a warm, airy place for a week. Then store them in a paper bag or box with peat moss. Keep them in a cool, dark spot around 45-50°F. Check monthly for rot and remove any bad ones.
Replant them indoors in late winter to get a head start again.
Treating As Annuals
If you don’t want to save tubers, simply pull up plants after frost kills them. Compost the debris. Buy new plants next spring. This is easier but costs more over time.
Best Begonia Varieties For Colorado
Some begonias handle Colorado’s conditions better than others. Here are top picks.
- Wax begonias (Begonia semperflorens): Tough, sun-tolerant, and bloom all summer. Great for beds and containers.
- Tuberous begonias (Begonia × tuberhybrida): Large, showy flowers in shade. Perfect for hanging baskets.
- Rex begonias: Grown for colorful foliage. Need more humidity, so they do well in terrariums or indoors.
- Dragon wing begonias: Angel-wing type with glossy leaves and red or pink flowers. Very heat tolerant.
Container Planting Tips
Containers warm up faster than ground soil. You can plant begonias in pots a week or two earlier. Use a high-quality potting mix with perlite for drainage.
Choose pots with drainage holes. Begonias hate sitting in water. Group pots together to create humidity. In Colorado’s dry air, this helps keep leaves from crisping.
Water containers more often than garden beds. They dry out fast in the sun. Check daily during hot spells.
Frequently Asked Questions
Can I Plant Begonias In April In Colorado?
Only if you protect them from frost. April is risky because soil is still cold and frost is common. Wait until late May for safety.
What Is The Latest Time To Plant Begonias In Colorado?
You can plant begonias through early July. They need at least 8-10 weeks of warm weather to bloom well. Later than July may not give enough time before fall frost.
Do Begonias Need Full Sun In Colorado?
No. Most begonias prefer morning sun and afternoon shade. Direct afternoon sun can burn leaves. Wax begonias are more sun tolerant but still need some shade.
How Deep Should I Plant Begonia Tubers?
Plant tubers about 1/2 inch deep with the concave side up. Cover lightly with soil. Deeper planting can cause rot.
Can I Leave Begonias In Pots Over Winter In Colorado?
Not outdoors. Bring pots inside before frost. Place in a bright, cool room and water sparingly. Or dig up tubers and store them as described above.
Final Thoughts On Planting Begonias In Colorado
Timing is everything for begonias in Colorado. Wait for warm soil and no frost risk. Prepare your soil well and choose the right spot. With proper care, these plants will reward you with color from June through September.
Remember to adjust for your specific microclimate. A garden in a warm valley may be ready earlier than one on a windy hill. Use a frost blanket if a late cold snap threatens after planting.
Begonias are forgiving plants. Even if you plant a bit late, they will catch up. Focus on consistent watering and feeding. Deadhead regularly for continuous blooms.
By following these guidelines, you will master the Best Time To Plant Begonia In Colorado. Your garden will be full of vibrant flowers that stand out against the Rocky Mountain backdrop. Enjoy the process and the beautiful results.