If you want a garden full of color, knowing when is the best time to plant phlox makes all the difference. Getting the timing right is the key to those vibrant spring blooms you’re dreaming of. This guide will walk you through the perfect planting windows, step-by-step instructions, and the simple care tips that ensure success.
Phlox are beloved for their clusters of fragrant flowers that can paint your garden in shades of pink, purple, white, and red. They attract butterflies and are surprisingly easy to grow once you understand their needs. The secret to a spectacular show is putting them in the ground at the optimal moment.
When Is The Best Time To Plant Phlox
There are two main types of phlox: tall garden phlox (Phlox paniculata) and creeping phlox (Phlox subulata). Their ideal planting times differ slightly, but both revolve around avoiding weather extremes.
For Spring-Blooming Creeping Phlox (Phlox subulata)
Creeping phlox, also called moss phlox, is the early bloomer that forms colorful carpets in spring. For this type, you have two excellent planting windows:
- Early to Mid-Autumn: Planting about 6 weeks before your first hard frost is ideal. The soil is still warm, which encourages root growth, but the air is cool. This gives the plant time to establish itself securely before winter dormancy, leading to a stronger bloom the following spring.
- Early Spring: As soon as the ground is workable and no longer frozen, you can plant. Do this just as the plant is emerging from dormancy. While you might get a few blooms that first year, the plant will focus more on root development, setting the stage for a better display in year two.
For Summer-Blooming Tall Garden Phlox (Phlox paniculata)
Tall phlox blooms later, in mid to late summer. Its planting schedule is similar but with a greater emphasis on autumn planting.
- Autumn is King: Again, the 6-weeks-before-frost rule is perfect. Autumn planting allows the perennial to develop a robust root system without the stress of summer heat. This leads to healthier plants and more prolific blooms the next summer.
- Spring Planting Option: You can plant in spring after the danger of frost has passed. Be prepared to water more diligently through the first summer, as the plant will be working hard to grow roots and foliage simultaneously.
Why Timing Matters So Much
Planting at the right time is not just a suggestion; it’s crucial for the plants survival and flowering potential. If you plant too late in autumn, the roots won’t have time to anchor before the ground freezes, which can cause the plant to heave out of the soil. Planting too early in spring in cold, soggy soil can lead to root rot.
The goal is to aim for mild conditions that promote root growth. Strong roots are the foundation for those vibrant blooms you want.
How to Plant Phlox for Success
Once you’ve chosen your time, follow these steps to give your phlox the best start.
Step 1: Choose the Right Location
Most phlox varieties thrive in full sun, meaning at least 6 hours of direct sunlight daily. They can tolerate light afternoon shade, especially in hotter climates. Good air circulation is vital for preventing foliar diseases like powdery mildew, so avoid cramming them against walls or other plants.
Step 2: Prepare the Soil
Phlox prefer rich, well-draining soil that holds moisture but never becomes waterlogged. Here’s how to prepare your planting site:
- Loosen the soil to a depth of about 12-15 inches.
- Mix in a generous amount of compost or well-rotted manure. This improves drainage, adds nutrients, and helps with moisture retention.
- If your soil is heavy clay, consider raising the planting bed or adding some coarse sand to improve drainage.
Step 3: Planting Your Phlox
- Dig a hole that is twice as wide as the plant’s root ball and just as deep.
- Gently remove the plant from its container and loosen the roots if they are pot-bound.
- Place the plant in the hole, ensuring the top of the root ball is level with the surrounding soil surface. Planting to deep can cause stem rot.
- Backfill the hole with your amended soil, gently firming it around the base of the plant.
- Water thoroughly to settle the soil and eliminate air pockets.
Step 4: Spacing for Health and Beauty
Proper spacing is non-negotiable for health. For creeping phlox, space plants about 15-18 inches apart. They will quickly fill in the gaps. For tall garden phlox, space them 18-24 inches apart. This ensures good air flow between mature plants, which is your best defense against disease.
Caring for Your Phlox After Planting
Your job isn’t done after planting. Consistent care, especially in the first year, is essential.
Watering Wisely
Keep the soil consistently moist but not soggy for the first growing season. This is critical for establishing those deep roots. A good rule is to provide about 1 inch of water per week, either from rainfall or supplemental watering. Water at the base of the plant to keep the foliage dry and prevent disease.
Once established, phlox are somewhat drought-tolerant, but they will bloom best with consistent moisture.
Mulching for Moisture and Weed Control
Apply a 2-3 inch layer of organic mulch, like shredded bark or compost, around your plants. This helps retain soil moisture, keeps the roots cool in summer, and suppresses weeds. Keep the mulch a few inches away from the plant stems to prevent rot.
Feeding for Vibrant Blooms
In early spring, apply a balanced, slow-release fertilizer or a top-dressing of compost around your plants. Avoid high-nitrogen fertilizers, as they will promote lush foliage at the expense of flowers. A second light feeding after the first bloom flush can help encourage more flowers on tall varieties.
Pruning and Deadheading
For creeping phlox, a light trim after blooming can help maintain a compact shape and encourage denser growth. For tall garden phlox, deadheading (removing spent flower clusters) can promote a second, smaller bloom period. In late fall or early spring, cut tall phlox stems back to about 2 inches above the soil.
Common Problems and Simple Solutions
Even with perfect timing, you might encounter a few issues. Here’s how to handle them.
- Powdery Mildew: This white coating on leaves is common in humid weather with poor air circulation. Choose mildew-resistant varieties, ensure proper spacing, and water at the base. Neem oil can be used as a treatment if needed.
- Spider Mites: These tiny pests cause stippled, yellow leaves. A strong spray of water from the hose can dislodge them. Insecticidal soap is an effective organic control.
- Poor Blooming: If your phlox isn’t blooming well, the culprit is usually to much shade, over-fertilization with nitrogen, or overcrowding. Reassess its location and care routine.
FAQ: Your Phlox Planting Questions Answered
Can I plant phlox in the summer?
It’s not recommended. Summer heat and drought stress can overwhelm a newly planted phlox. If you must, plant on a cloudy day, water extremely diligently, and provide temporary shade.
Is fall or spring better for planting phlox?
For both types, early fall is generally the best time to plant phlox. The conditions are perfect for root growth without the demands of top growth or extreme heat.
How deep should I plant my phlox?
Plant at the same depth it was growing in its nursery pot. The crown (where the stems meet the roots) should be at soil level, not buried.
Can I divide and replant my phlox?
Absolutely! Dividing every 3-4 years in early spring or early fall rejuvenates crowded clumps. Simply dig up the plant, gently separate it into smaller sections with healthy roots and shoots, and replant immediately.
Do phlox come back every year?
Yes, both creeping and tall garden phlox are herbaceous perennials. They die back to the ground in winter and regrow from their root system each spring.
By following this guide on the best planting times and care, you’ll set the stage for a stunning display. Remember, patience is key—a well-planted phlox might take a season to settle in, but the reward of those vibrant, long-lasting blooms is well worth the wait. Your garden will be buzzing with color and life for seasons to come.