Colorado gardeners face a unique challenge when August heat meets the need for resilient blooms. Finding the best flowers to plant in august in colorado means choosing varieties that can handle intense sun, dry soil, and sudden afternoon thunderstorms.
August in Colorado is hot. Your garden might look tired. But you can still add color and life. The key is picking flowers that love heat and don’t mind a little drought.
This guide covers the top flowers for late summer planting. You’ll get tips for success in Colorado’s high-altitude climate. Let’s dig in.
Best Flowers To Plant In August In Colorado
August planting requires tough plants. Colorado’s sun is strong. The soil can be rocky or clay-heavy. But many flowers thrive here if you choose wisely.
Here are the top picks for August planting in Colorado gardens.
Marigolds
Marigolds are heat champions. They bloom non-stop from planting until frost. These bright orange and yellow flowers attract pollinators and repel pests.
- Plant in full sun
- Water deeply once a week
- Deadhead spent blooms for more flowers
- Great for borders and containers
Zinnias
Zinnias love Colorado summers. They grow fast from seed or transplants. Colors range from pink to red to purple. They handle dry conditions well.
- Sow seeds directly in August
- Space plants 6-12 inches apart
- Water at the base to avoid mildew
- Cut flowers for indoor bouquets
Cosmos
Cosmos are low-maintenance and drought-tolerant. Their daisy-like flowers sway in the breeze. They self-sow, so you get free plants next year.
- Plant in poor soil for best blooms
- Full sun required
- Thin seedlings to 12 inches apart
- No fertilizer needed
Sunflowers
Sunflowers grow quickly and bring height to gardens. August planting gives you late-season blooms. Choose shorter varieties for better wind resistance.
- Plant seeds 1 inch deep
- Water regularly until established
- Stake tall varieties
- Harvest seeds for birds or snacks
Petunias
Petunias handle heat and keep blooming. They come in trailing and upright forms. Use them in hanging baskets or ground beds.
- Plant in well-drained soil
- Water when top inch feels dry
- Fertilize every two weeks
- Pinch back leggy growth
Salvia
Salvia is a Colorado native favorite. It attracts hummingbirds and bees. The spiky flowers come in blue, purple, red, and white.
- Full sun is best
- Drought-tolerant once established
- Cut back after first bloom for repeat flowers
- Deer resistant
Portulaca
Portulaca is a succulent ground cover. It thrives in poor, dry soil. Flowers open in sun and close at night.
- Plant in hot, dry spots
- Water sparingly
- Great for rock gardens
- Self-seeds easily
Gaillardia
Gaillardia, or blanket flower, is a Colorado native. It blooms from June to frost. The red and yellow daisies are stunning.
- Plant in full sun
- Well-drained soil essential
- Deadhead for continuous bloom
- Very drought-tolerant
Lantana
Lantana loves heat and humidity. It works well in containers or as a bedding plant. Flowers change color as they age.
- Full sun required
- Water when soil is dry
- Fertilize monthly
- Can be overwintered indoors
Verbena
Verbena is a low-growing spreader. It produces clusters of small flowers in purple, pink, or red. It’s perfect for borders.
- Plant in full sun
- Good drainage is key
- Water regularly during dry spells
- Cut back after blooming
Why August Planting Works In Colorado
August soil is warm. Seeds germinate faster. Transplants establish quickly. The days are still long, giving plants plenty of light.
Colorado’s monsoon season brings afternoon rain. This helps new plants settle in. But you still need to water during dry periods.
Planting in August gives you color through September and October. Some flowers last until the first hard frost, which can be as late as October.
Benefits Of Late Summer Planting
- Warm soil speeds root growth
- Fewer weeds to compete
- Less watering needed than spring
- Extended blooming season
- Lower risk of frost damage
How To Prepare Your Colorado Garden For August Planting
Good soil prep makes a big difference. Colorado soil is often alkaline and low in organic matter. Here’s how to get it ready.
Step 1: Test Your Soil
Get a simple soil test kit. Check pH and nutrient levels. Most flowers prefer slightly acidic to neutral soil (pH 6.0-7.0).
Step 2: Amend The Soil
Add compost to improve drainage and fertility. Mix in 2-3 inches of organic matter. This helps sandy soil hold water and clay soil drain better.
Step 3: Remove Weeds
Pull weeds before planting. They compete for water and nutrients. Use a hoe or hand pull.
Step 4: Water Deeply
Water the planting area a day before you plant. This gives roots a moist start. Deep watering encourages deep root growth.
Step 5: Plant At The Right Depth
Follow seed packet instructions. Transplants should be at the same depth as their pot. Firm soil around roots gently.
Step 6: Mulch
Add 2-3 inches of mulch. This keeps soil cool, retains moisture, and suppresses weeds. Use wood chips, straw, or shredded leaves.
Watering Tips For August Flowers In Colorado
Watering is critical in August. Colorado’s low humidity and intense sun dry soil fast. But overwatering causes root rot.
How Often To Water
- New plants: Water daily for first week
- Established plants: Water 2-3 times per week
- Check soil moisture 1 inch deep
- Water early morning to reduce evaporation
Best Watering Methods
- Soaker hoses deliver water to roots
- Drip irrigation is efficient
- Avoid overhead watering to prevent disease
- Water deeply, not frequently
Common Mistakes When Planting Flowers In August
Avoid these errors for best results.
Planting Too Late
Some flowers need time to bloom before frost. Check days to maturity on seed packets. Choose fast-growing varieties.
Overwatering
Too much water causes yellow leaves and root rot. Let soil dry between waterings. Use your finger to test moisture.
Ignoring Sun Exposure
Colorado sun is intense. Even full-sun flowers may need afternoon shade in August. Watch for leaf scorch.
Skipping Mulch
Bare soil dries fast and heats up. Mulch protects roots and keeps soil temperature stable.
Forgetting Fertilizer
August flowers need nutrients. Use a balanced, slow-release fertilizer. Avoid high-nitrogen formulas that promote leaves over blooms.
Best Flowers For Colorado’s High Altitude
Higher elevations have cooler nights and stronger UV. Choose flowers that tolerate these conditions.
For Mountain Gardens (Above 7,000 Feet)
- Rocky Mountain Penstemon
- Columbine (Colorado state flower)
- Blanket Flower
- Yarrow
- Ice Plant
For Front Range Gardens (5,000-7,000 Feet)
- Marigolds
- Zinnias
- Cosmos
- Petunias
- Salvia
How To Extend Bloom Time Into Fall
With care, your August-planted flowers can bloom until frost. Here’s how.
Deadhead Regularly
Remove spent flowers. This tells the plant to produce more blooms. Do it weekly for best results.
Fertilize Lightly
Apply a bloom-boosting fertilizer every 2-3 weeks. Use a formula high in phosphorus. Follow package directions.
Protect From Early Frost
Cover plants with row covers or old sheets if frost is forecast. Remove covers in the morning. This adds weeks to the season.
Water Consistently
Don’t let plants dry out completely. Stress reduces blooming. Keep soil evenly moist but not soggy.
Container Gardening For August Flowers
Containers are great for Colorado gardens. You can move them to catch sun or avoid storms. They also warm up faster in spring.
Best Containers
- Terra cotta pots (breathable but dry fast)
- Plastic or glazed pots (hold moisture longer)
- Fabric grow bags (good drainage)
- Self-watering containers (reduce watering frequency)
Potting Mix
Use a high-quality potting mix. Add perlite or vermiculite for drainage. Avoid garden soil, which compacts in pots.
Planting Tips
- Choose dwarf or compact varieties
- Group plants with similar water needs
- Fertilize more often than in-ground plants
- Check soil daily in hot weather
Native Colorado Flowers For August Planting
Native plants are adapted to local conditions. They need less water and care. They also support local wildlife.
Top Native Choices
- Purple Coneflower (Echinacea)
- Black-Eyed Susan (Rudbeckia)
- Butterfly Weed (Asclepias tuberosa)
- Blue Flax (Linum perenne)
- Rocky Mountain Bee Plant
Benefits Of Natives
- Drought-tolerant once established
- Attract native pollinators
- Less fertilizer needed
- Resistant to local pests
- Lower maintenance overall
Dealing With Colorado Pests In August
August brings aphids, spider mites, and grasshoppers. Here’s how to protect your flowers.
Common Pests
- Aphids: Spray with water or insecticidal soap
- Spider mites: Increase humidity, use neem oil
- Grasshoppers: Use floating row covers
- Slugs: Hand pick or use diatomaceous earth
Prevention Tips
- Keep garden clean of debris
- Encourage beneficial insects like ladybugs
- Rotate plant families each year
- Water at soil level to avoid wet leaves
Frequently Asked Questions
Can I plant flowers in August in Colorado?
Yes, August is a great time. Choose heat-tolerant varieties like marigolds, zinnias, and cosmos. Water consistently and mulch well.
What are the best flowers to plant in August in Colorado?
Top choices include marigolds, zinnias, cosmos, sunflowers, petunias, salvia, portulaca, gaillardia, lantana, and verbena. All handle heat and bloom until frost.
How late can I plant flowers in Colorado?
You can plant until mid-August for most flowers. Fast-growing varieties can be planted into early September. Check days to maturity on seed packets.
Do I need to water more in August?
Yes, August is hot and dry. New plants need daily water for the first week. Established plants need 2-3 times per week. Always check soil moisture.
What flowers bloom all summer in Colorado?
Marigolds, zinnias, petunias, salvia, and gaillardia bloom from planting until frost. Deadhead regularly to encourage continuous flowers.
Final Tips For August Flower Success
Start with healthy plants. Check for pests before buying. Water deeply and less often. Mulch to keep roots cool.
Watch the weather. Colorado storms can be sudden. Protect young plants from hail with buckets or row covers.
Enjoy your garden. August planting gives you color when many gardens fade. You’ll have blooms through September and into October.
Share your success with neighbors. Colorado gardening is a community. Your flowers might inspire someone else to plant in August.
Remember, the best flowers to plant in August in Colorado are the ones that match your garden’s conditions. Start with a few varieties and expand next year. Every season teaches you something new.
Happy planting. Your Colorado garden will thank you.