Encouraging Phlox to Spread

Keys Takeaways 

Phlox are popular perennial plants known for their colorful spring and early summer flowers. They emerge early each year and readily self-seed to create large clusters in gardens over time. Here are the key takeaways for encouraging phlox plants to spread:

  • Provide ideal sunlight and soil conditions. Phlox prefers full sun but tolerates light shade. They thrive in organically rich, well-drained soil.
  • Leave spent flowers on the plants. Allowing faded phlox flowers to go to seed encourages self-sowing and spreads plants.
  • Divide mature clumps. Carefully dig up and divide large, overgrown clumps every 2-3 years to rejuvenate growth.
  • Plant in drifts. Group multiple phlox plants together in sweeping drifts through beds and borders for a fuller, cascading growth habit over time.

Sun and Soil Needs for Healthy Phlox Growth


Phlox is not too demanding in terms of care, but providing the right amounts of sun and amending soil to have good drainage is key for success with the plants.

Sun Requirements

  • Full sun: Ideally 6+ hours of direct sunlight per day
  • Light shade: Will tolerate 3-6 hours of sun
  • Heavy shade: Not recommended, leads to fewer blooms

Soil Specifications

  • Nutrient-rich: Mix in compost or aged manure before planting
  • Well-draining: Sandy or loamy soils that won’t get waterlogged
  • Neutral pH: Test soil and amend to reach pH 6.5-7.5 if needed

Preparing a Site for Planting

When introducing phlox to a new garden bed or border, prep the site properly by:

  • Removing weeds, debris, or unhealthy plants
  • Working organic compost thoroughly into the top 6-12 inches
  • Loosening compacted earth to improve drainage
  • Watering deeply to hydrate soil before planting

Caring for Phlox Through the Seasons

Here is an overview of key care phlox required in each part of the growing season:

SeasonCare Needs
Spring– Cut back dead growth from winter
– Water if rainfall is low
Summer– Pinch off spent flower heads
– Occasional watering in drought
Fall– Prune back leggy stems after bloom
– Leave seed heads for self-sowing
Winter– Mulch plants to protect roots if very cold

Techniques to Expand Phlox Through Self-Seeding

With proper care and optimal site conditions, phlox readily self-sow, expanding clusters each year. Here are some key techniques to really maximize self-seeding from your plants:

Leave Spent Blooms

Instead of deadheading, allow faded phlox flowers to dry out and drop their seeds:

  • Seeds fall around the mother plant and take root easily
  • Self-sown plants create dense drifts, cascade over time
  • Can get hundreds of seedlings each year

Transplant Extra Seedlings

For even more new plants:

  • Carefully dig up and pot extras sprouting adjacent to the original plants
  • Transplant seedlings to other beds, borders, or share with gardener friends!

Scatter Seeds

In late fall, harvest dry seed heads and manually scatter seeds:

  • Mimics natural self-seeding
  • Place seeds along pathways, edges of low borders
  • Cover lightly with 1⁄4” soil

Dividing Overgrown Phlox Clumps

Mature phlox sends up many stems and becomes overgrown after 2-3 years. Dividing the roots rejuvenates the plants:

When to Divide

  • Spring and early fall are the best seasons
  • Avoid summer heat or winter dormancy periods

Division Process Step-By-Step

  1. Use a garden fork to loosen the soil and carefully lift the entire plant
  2. Shake off excess soil then separate sections with a knife or pruners
  3. Replant divisions 12-18” apart to allow for future spreading
  4. Water gently until established

Each division will grow rapidly again when given space and ideal conditions!

Designing With Phlox for Gorgeous Garden Drifts

There are over 50 popular phlox species and varieties available, with options spanning various heights, colors, and growth habits.

Incorporate different types together to create beautiful, natural-looking garden drifts:

Combine These 3 Phlox Groups:

  • Tall phlox – Fragrant large-clustered back of border flowers
  • Creeping phlox – Mat-forming carpets loaded with blooms
  • Border phlox – Medium height with bold flower heads over mounds of foliage

Complementary Color Palettes

Group compatible hues for stellar displays:

  • Blue phlox with purples and whites
  • Pink or coral phlox with red and orange flowers
  • Pastel mixes: lavender, peach, cream varieties

Consistent Watering is Key!

To prevent disease issues:

  • Ensure Phlox gets regular water
  • Quick drying avoids potentially harmful mildew problems
  • Space/thin plants for adequate air circulation

Continual Care of Established Phlox Plantings

With mature, expanding phlox stands, sustain beauty and flowering with attentive yearly maintenance:

Regular Division

Thin congested areas and give away extras to share the perennial bounty!

Occasional Cut Backs

Prune leggy stems mid-summer to prompt bushier regrowth.

Clean Up Dead Foliage

Remove tattered leaves before winter to improve appearance.

Monitor for Pests

Watch for signs of phlox plant bugs; control with neem oil or insecticidal soap sprays if found.

Weed Vigilantly

Pull emerging weeds to keep beds clean for phlox to spread nicely into space.


With bright, fragrant, summer-long blooms and the ability to quickly spread into impressive stands, phlox is one of the best self-seeding perennials for adding color, texture, and charm to gardens.

Follow the tips outlined here for encouraging lush, flowing phlox that develops gorgeously over time with little effort on your part as the gardener. Soon you’ll have plenty of phlox to share so friends can enjoy their beauty as groundcovers, borders, cut flowers, and more!

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