Getting it to bloom

Why won't my Smooth Phlox bloom? (and how to make it flower)

Also called Smooth Phlox, Marsh Phlox (Phlox glaberrima).

More about smooth phlox

About Smooth Phlox

Phlox glaberrima · also called Smooth Phlox, Marsh Phlox · flowering

A clump-forming native perennial valued for its mildew-resistant foliage and clusters of fragrant pink to magenta flowers in late spring. It tolerates more soil moisture than most phlox, thriving along stream edges or in moist borders. Plant in full sun to light shade in fertile, consistently moist soil and divide clumps every 3–4 years to maintain vigour.

Plant type: flowering

Watch for — Self-seeding: Deadhead spent flower clusters promptly to prevent excessive self-seeding and to extend the bloom period by encouraging new flower stems.

The reasons smooth phlox isn't blooming

Almost every non-blooming smooth phlox traces back to one of these, roughly in order of how common they are:

Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.
Too much nitrogen feed, driving lush foliage at the expense of flowers (very common with general or lawn feeds).
The plant has not been deadheaded, so it stops flowering once it sets seed.
Irregular watering — drought or waterlogging at the budding stage makes buds abort.
It is still too young or was checked by a transplant and is rebuilding before flowering.

Feeding smooth phlox a high-nitrogen general feed and growing it in too little sun — you get a big leafy plant and almost no flowers.

The fix — how to get smooth phlox to flower

Maximise sun. Give smooth phlox the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers.
Switch the feed. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.
Deadhead regularly. Remove spent flowers often to keep it producing more rather than stopping to set seed.
Water consistently. Keep moisture even through budding and flowering — drought-then-flood swings make buds drop.

Light and feeding do most of the heavy lifting here. Dial in the spot with the light guide for smooth phlox and get the feeding right with the smooth phlox fertilising schedule — the wrong feed (too much nitrogen) is one of the most common silent reasons a healthy plant makes leaves instead of flowers.

Bloom season and what to expect

Smooth Phlox flowers across its growing season (mostly summer) and, kept fed and deadheaded, can bloom for many weeks or right up to frost.

Post-bloom care so it flowers again

Deadhead, keep feeding lightly, and many will rebloom; collect seed from the best plants at the end of the season if you want to grow them again.

For everything else this plant needs day to day, see the full smooth phlox care brief and its watering schedule — a stressed, badly watered plant rarely has the energy to flower at all.

Smooth Phlox blooming — frequently asked questions

Why won't my smooth phlox flower?

Smooth Phlox blooms on the season's growth given enough sun, warmth and the right feed — there is no cold or photoperiod trick, just good growing conditions and a bloom-leaning feed. The most common reason it is not happening: Too little sun — most of these need full sun (or very bright light) to flower well; shade gives leaves, not blooms.

How do I make smooth phlox bloom?

Give smooth phlox the sunniest spot you have — for most bedding and fruiting plants, more direct light directly means more flowers. Move off high-nitrogen feeds and use a higher-potassium "bloom" or tomato-type feed as it comes into flower.

When does smooth phlox normally bloom?