General gardening topics

How to plant and grow garden phlox

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Garden phlox is a stunning plant with its billowy blooms and slender stature, something perfect for adding height to your garden especially in the summer. Not only is the plant itself quite stunning and very easy to maintain but the flowers have an incredibly long flowering season that often starts as early as July and continues through until as late as September.

Available in a range of colours colour including white, yellow, pink, red and even shades of blue that are next to impossible to find in any other plant. So if you are looking to grow phlox in your garden, keep reading.

Types of phlox

The first thing to note is you can get both traditional perennials types that grow upright, how you might think of most herbaceous perennials for cottage gardens, these include Phlox Paniculata. You can also get smaller, ground spreading phlox often sold as rockery plants that are great for ground cover at a very low level such as Phlox subulata which is a creeping perennial.

This perennial plant is native to Woodlands around the world and brings with it beautiful strength and cover for your yard. This perennial does not need to be replaced which is what makes it so effective as ground cover.
Phlox subulata

Garden phlox, sometimes called border phlox or summer phlox is a native to Europe originally cultivated in England and Germany before it was exported to the United States. Large upright varieties can reach up to one meter in size at full maturity but most it’ll reach around 50cm.

Look out for varieties with a sweet fragrance and variegated foliage

It is known for dainty flowers with five petals packed together in dozens of panicles the size of which can range between 9 and 15cm tall and 15 to 20 cm wide. The flowers are not only beautiful but often adorned with contrasting colours and a sweet fragrance. The foliage can be variegated as well as incorporating yellow margins or creamy white centre.

Most flower between July and September

Most phlox will flower between July and September but if you choose a variety of cultivars that have been bred for longer flowering times that can start to flower a little bit later in the season or a little bit earlier in the season.

Consider mixing earlier flowering varieties with later flowering varieties

When you go to look for different phlox to grow in your garden, you will find that they are categorized as early-season flowering, late to midseason flowering, and late-season flowering. If you plant all three of these you can enjoy flowers from the beginning of Summer well into the end of autumn.

Growing Phlox

Growing phlox

Phlox grow well in full sun but will also grow well with a little shade

Phlox will produce the best flowers if it is given full sunlight. However, phlox are native woodland plants so they will tolerate a little bit of shade especially if you live in the southern regions of the UK that are a bit warmer in climate.

Plant in fertile well-drained soil

The soil in which you grow them needs to be fertile and well-drained, slightly alkaline but they will tolerate most soil types. If you have slightly acidic soil and you are set on growing phlox in your garden, regularly applying lime to the soil can help make the ph level more suitable. 

How to plant phlox

When you plant phlox in your garden, you need to put them in the ground in the springtime after any danger of frost is over which is usually May in the Uk. You can buy them at any time of year as potted plants but you can also get bare-root plants when they are dormant and they are often cheaper.


Space plants at least 20cm apart to ensure proper air circulation between multiple plants, this helps prevent mildew which can be a problem with phlox.

After you put them in the ground, thoroughly water them and give them a layer of mulch around the base to keep the roots cool.

Growing from seed

If you choose to start them from seeds you have to start them indoors at the end of winter and once germinated pot them on into smaller pots until established. You can move them outside in the spring when the risk of frost has passed.

Regular care


Make sure that you give them water during any dry spells especially if growing them in pots and containers as they often dry out quickly. If you notice the foliage starting to wilt, you should give them more water but also being careful not to overwater. It is always better to water at the base rather than on top of the plant.

Dividing phlox

Phlox plants are best divided every few years so in his guide we look at how and when to divide them to get the most out of them and how to keep them flowering

To prevent overcrowding you will have to divide your phlox every 3 or 4 years as you do with most perennials. If you notice that they are not flowering as prolifically as they once did or the centre of the plant dying out it’s indicative of division time.

Learn more about how and when to divide phlox in this guide

Cutting back plants to promote bushier plants

These plants don’t normally require pruning but you can force the plants to become bushier by pinching back the stems by 1/3 at the beginning of summer. You can also deadhead and he spent flowers to prevent it from reseeding and to extend the flowering period.

Cut back your stems to just above the soil line and then protect the roots by adding a layer of mulch before the ground freezes in very cold areas.

Dealing with powdery mildew fungus

Phlox suffers heavily from powdery mildew but it mostly affects the taller upright varieties and not the creeping varieties. This fungus will attack the leaves and the result will be shrivelled and grey leaves, the last thing you want in your garden.

This is very prevalent when the weather gets warm and plants that are grown in partial shade or more susceptible. Improving the air circulation as already mentioned, keeping the plants properly spaced when you first plant them into your garden will go a long way toward preventing this. You can also use mildew-resistant cultivars if your garden has suffered from this before.

We recommend spraying with a fungicide as soon as you see signs of mildew to try and help combat and prevent it from spreading but its often an ongoing battle.

Welcome to my site, my name is John and I have been lucky enough to work in horticultural nurseries for over 15 years in the UK. As the founder and editor as well as researcher, I have a City & Guilds Horticultural Qualifications which I proudly display on our About us page. I now work full time on this website where I review the very best gardening products and tools and write reliable gardening guides. Behind this site is an actual real person who has worked and has experience with the types of products we review as well as years of knowledge on the topics we cover from actual experience. You can reach out to me at

1 Comment

  1. Anonymous

    That was hugely helpful and enlightening – thank you 🙂

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