How to Grow Phlox Drummondii (Annual Phlox)

There are more than 60 different species of phlox, each with its own unique characteristics and benefits. For its part, phlox drummondii—commonly known as annual phlox—brings a big dose of color to the table.

Native to Texas, phlox drummondii was discovered by Thomas Drummond during the early 1800s in his home state of Texas, but quickly grew to fame in England and other parts of Europe, thanks to its ease of care and the bright, saturated hues of its trumpet-shaped blooms.

Best planted in either the spring or fall, phlox drummondii will grow at a moderate pace, often reaching maturity after two to three years' time. However, it will bloom within its first year, making it a great plant to enjoy even in its juvenile stages.

Phlox Drummondii Care

Phlox drummondii is an abundant wildflower that grows exceedingly well, even with limited time and attention. To make the most of this blooming beauty in your garden, be sure to plant in an area with sufficient sunlight and feed it regularly.

Deadhead phlox drummondii regularly can encourage continued flower production and minimize self-seeding. However, some gardeners let the plant self-seed and therefore successfully avoid needing to replant this annual flower year after year.

Light

Like many other flowering plants, annual phlox needs a decent amount of sunshine in order to produce the colorful blooms it's known for. It does best when planted in garden positions that get at least six to eight hours of sun each day during the growing season. That said, if you live in a region with extremely hot and sunny weather, your phlox plants may actually do better located in partial shade, where they’ll be protected from intense heat.

Soil

Often found in grasslands and meadows, phlox drummondii can adapt to a variety of different soil conditions, as long as the ground is well-draining. The ideal planting environment for phlox drummondii is loose, sandy soil that's rich in nutrients. Additionally, the soil's pH levels should be slightly acidic, though it can grow well in neutral soil as well.

Water

Phlox drummondii plants appreciate consistently moist conditions during their growing season. If you live in an area with particularly low rainfall, it's likely that you will need to water them frequently throughout the summer, increasing your cadence if the weather is especially hot.

Temperature and Humidity

Native to the hot, dry climate of the southeastern United States, phlox drummondii loves warm weather and plenty of sun. It can tolerate temperatures as low as 30 degrees Fahrenheit, but it will cease blooming in that type of environment. Additionally, it's not a humidity lover—too much ambient moisture can lead to fungal issues for the plant.

Fertilizer

To put on a show each summer, phlox drummondii will need sufficient soil nutrients to support lush foliage and abundant flowering. For this reason, these plants do best planted in fertile soil. If your soil is lacking in nutrients, then an application of fertilizer during the growing season will be necessary. However, keep in mind that too much nitrogen can lead to leggy growth and poor flowering performance.

If you’re unsure of your soil’s nitrogen levels, get a soil sample analyzed and make fertilizer decisions based on the NPK (nitrogen, phosphorous, potassium) of your dirt. In general, flowering plants do well with a fertilizer formula that has a higher ratio of potassium when compared to nitrogen and phosphorous. Also skip foliar fertilizers (applied to the leaves), since the sticky, hairy leaves of phlox drummondii will hinder nutrient absorption. 

Varieties of Phlox Drummondii

• Phlox drummondii ‘Phloxy Lady’: This cultivar is intended to bloom longer than conventional annual drummondii. It features blooms in vibrant shades of red, pink, purple, and white.
• Phlox drummondii ‘Giselle Hot Pink’: This cultivar is available in a number of shades, including a hot pink variety. These phlox plants demonstrate even greater tolerance to heat and are an ideal option for gardens or containers where you want a pop of intense, dynamic color.
• Phlox drummondii ‘Pop Stars’: The most unique thing about this variety of annual phlox is its star-shaped blossoms.

Propagating Phlox Drummondii

Phlox drummondii is most commonly propagated by seed. The seeds for these plants are widely available commercially, but you can also collect them from the spent blossoms of mature plants you may already have. To do so, look for the small seed pods at the base of wilted blooms. When dry, the pods will easily split open to reveal the small, brown seeds inside.

Plant annual phlox seeds in the garden a couple of weeks before the last expected spring frost. If you want to begin growing your seedlings even sooner, you can start the seeds in a container and transplant them outdoors at a later date.

Potting and Repotting Phlox Drummondii

Phlox drummondii is a great candidate for growing in containers. With their mounding growth habit and bright blooms, these plants are a cheery option for window boxes, hanging planters, or container gardens. When growing phlox in containers, keep in mind that these plants have a 1- to 2-foot spread and plant them accordingly. You should also take steps to ensure the container you choose has sufficient drainage. Without this, the roots can become soggy leading to rot problems or poor crown growth.

Common Pests & Diseases

Phlox can face a few issues when it comes to pests and diseases, specifically fungal diseases. Climates with high humidity can lead to powdery mildew problems on the leaves of the plant. Watering from the roots and minimizing splashing on the foliage of the plant can assist in preventing this problem.

Phlox plants are typically susceptible to spider mites and phlox plant bugs. If you notice signs of an infestation, treat your plant with a horticultural oil, like neem oil.