When to Plant Phlox – Planting Guide 2024

Save for later!

An easy perennial to grow, phlox comes in many different shades of colors and is a fan-favorite with gardeners. Learn when to plant phlox and how to best care for it so that you have a vibrant garden.

When to plant phlox: Phlox is a gorgeous plant that produces multiple blooms with small, star-like blossoms. It is almost always a perennial plant and should be treated as such. The best time to plant phlox is in the spring. While you can technically start it from seed, not many gardeners do so. It is hard to grow from seed and you aren’t always promised the best results. Instead, plant phlox from transplants or cuttings. Wait until after the threat of frost has passed in the spring before planting. Another good time to plant phlox is in the fall. Be sure to get the plant into the ground a month before your first fall frost date. This way the plant can spread its roots around and establish itself before the threat of cold winter weather.

Phlox will continue to grow each year. You should divide the plant every three years to keep it nice and healthy. The biggest threat to phlox is powdery mildew. To avoid this, always water the soil and not the plant. Also, spread your phlox out to create enough airflow.

Planting Phlox in Different Climates

Tropical Climate

Phlox is a perennial that needs a cold winter to survive A tropical climate does not often have these temperatures.

However, you can try a medium-height annual phlox. While it doesn’t like hot temperatures, it only lasts for one year and so it doesn’t need a cold winter.

Dry Climate

Phlox prefers moist soil. However, it does not like its roots to become soggy. You can try growing phlox in a dry climate as long as you hand-water your plants.

Temperate Climate

Phlox will do well in a temperate climate. The only factor to consider is the most springs. Phlox does not like soggy water and is susceptible to powdery mildew. If you live in a rainy area and still want to grow phlox, look for varieties that are more resistant to powdery mildew.

Continental Climate

One of the best climates for phlox is a continental climate. The spring is not too wet and the winters are cold to allow for a dormant period.

Polar Climate

Unfortunately, a polar climate will not have enough warmth or sunshine to sustain phlox plants.

Choosing Phlox Seeds

There are three size categories of phlox so you can choose one that works best for your garden or mix and match all of them.

Low-growing Phlox

Also known as creeping phlox, this smaller plant makes for excellent ground cover.

Woodland phlox prefers full shade and moist soil. It has flowers that have a blue shade to them.

Moss phlox spreads out slowly and will produce a mount-like plant. It is about 4 inches thick and great for rock gardens.

Medium-height Phlox

If you have gaps in your garden and aren’t sure what to plant, this category will beautifully fill in any space.

Annual phlox, as the name suggests, is actually an annual, unlike most other varieties of phlox. It does not like a lot of heat and prefers soil that is not too moist.

Tall-height phlox

Perfect for the back of a garden or set against a fence, this category will add a lovely depth to your garden.

Garden phlox is perhaps the most common of all the varieties. It is what you will normally see in a garden. This variety can grow between 3 and 5 feet tall and its flowers will last well into summer.

How to Plant Phlox Seeds


Generally, most varieties of phlox prefer partial to full sun. However, there are some types that actually prefer shade.

More common, taller varieties like the sun while woodland species have a natural shady habitat. It’s important to carefully read the growing specifications on your variety of phlox before you purchase or plant them.

Soil preferences

Be sure to plant your phlox, no matter the variety, in an area that has nutrient-rich soil. You can prepare the soil ahead of planting by placing compost or manure into the soil.

You also want soil that is moist but still drains well. Phlox does not like it when its roots are sitting in water, so you want to make sure the soil makeup is the right consistency.

If you have compacted soil, be sure to dig it up before planting as this will provide more oxygen into the soil. It will also allow the roots to grow better.

Seeds vs transplants

While you can grow phlox from seeds, most gardeners do not grow this route. It can be time-consuming and you aren’t guaranteed the best results.

Instead, try starting with either cuttings or transplants. Then, you can start the growing season off with full confidence that your plants will thrive.

Interestingly, however, is that phlox will often self-seed. Once your phlox is established, it might just spread over via seeds that fall to the ground.


The best time to plant phlox is in the spring. You should always wait until the threat of frost is over, which will depend on your climate. May is usually a good time to plant.

An alternative is to plant your phlox in the fall. You probably don’t want to plant if your winters are very cold as the plant might not be established enough to withstand the cold snap.

If you plant in the fall, do so at least one month before your first frost date. September is usually a good month to plant.

Digging the hole

If you choose to transplant small phlox plants, then you should mark out where to plant them. Phlox doesn’t grow to be too wide but you should still give it space to reach its full maturity.

Dig a hole that is twice the size of your phlox’s root ball. Then, place the plant inside the hole so that the tops of the roots are level with the ground surface. Fill the hole with soil and tamp it all down.

How to Water Phlox

Phlox can need a bit more water than other plants. This is especially true during the first year of its growth.

After planting, give your phlox plenty of water. Then, stick to a schedule so that it gets enough moisture.

Aim to water your phlox every two days, or daily during the summer. If there is no rainfall, you may need to water more often.

How to Grow Phlox

Compost and Mulch

Get into the habit of giving your phlox some love each spring. You can add a layer of compost to the soil around your phlox.

The compost layer should be thin and you can mix in a bit of soil if need be. This will give your phlox an extra injection of nutrients.

Then, on top of the compost, you can add a thicker layer of mulch. The bark mulch will stop weeds from growing and will also keep the soil moister.


Your phlox can flower from mid-spring into summer. To help this process, remove any dead or wilted flowers from the plant.

Your phlox plant will then continue to re-bloom throughout the season.

Perennial care

Phlox is a perennial plant, so it will continue to grow each year. You can clean the plant up a bit after it stops blooming but you don’t want to get rid of all the foliage until the fall.

Varieties of tall phlox need a bit more care. Wait until the first frost date in the fall and then cut the stems back so that they are about two inches from the soil.

Another way to keep phlox happy is to divide it. Every two to three years, divide your tall phlox plants so that there is enough breathing room around the plants.

Pests and Diseases

A common disease with phlox is powdery mildew. This happens when the foliage gets a lot of water.

To prevent powdery mildew from forming, try to water the ground around the flowers and not the plant itself. Furthermore, the plants should be spaced out enough so that there is ample airflow.

One benefit of phlox is that it is deer resistant. The flowers can be a bit fragrant, which will repel deer. If you live in a rural area, this is a great plant to grow as it usually remains untouched by deer.

How long does phlox take to grow?

Most gardeners plant young phlox plants or cuttings in the spring. Then, come mid-spring or early summer, you can expect blooms to form.

Phlox is a perennial so your plant will grow a bit larger each year you care for it.


With its star-like blossoms, phlox is an excellent addition to any garden. You can find ground cover varieties or tall varieties for more statement pieces. Plant your phlox in the spring and each year it will continue to grow.

Related Articles:

Save for later!

Leave a Comment