How to grow phlox in pots – expert advice for a spectacular patio plant that will erupt with color in summer

I’ve grown several varieties of phlox over the years, but one border in South Wales really sticks in my mind. A private garden with a vast romantic border that brimmed with cottage garden favorites – delphinium, rose, campanula – and in among them, drifts of phlox.

There was one called Phlox paniculata ‘Blue Paradise’, which grew to about three feet, with deep violet-blue flowers that seemed to glow when the light hit them. While I have grown many, I think this might be the ultimate tall phlox I have grown, and can't recommend it enough.

And while phlox are often grown in borders – they do like room to spread – I’ve found they can do just fine in pots too, so long as the container is large enough (some can grow up to three or even five feet). So, if you want to try these long-flowering perennials in containers, here’s everything I know about how to grow phlox in pots.

How to grow phlox in pots

Learning how to grow phlox in pots is a good option for small gardens or balconies. And, not only do these perennials add height and structure to displays, but they can go on flowering right through to the first frost. Given a little support (to fend off high winds), I have seen phlox flowers stand right up until November.

Caring for phlox in pots

There are many different Phlox spp., including low-growing creeping phlox. For pots, however, you want to use something with height and shape, so I suggest Phlox paniculata, otherwise known as garden phlox or border phlox.

Phlox paniculata is native to North America and is hardy down to zone 4, and is ideal for use in pots and containers. Reaching up to three or four feet, I know that this species can survive tough and cold winters without any additional care, so it is ideal for low-maintenance container gardeners.

Choose a pot that is a good size, at least 14 or 16 inches in diameter, to avoid any top-heavy tumbles towards the latter end of summer and fall.

Try these rustic pots, available from Amazon, which would work well when planted with phlox.

Then, use a good-quality potting mix combined with a few generous handfuls of horticultural grit or perlite to ensure that water moves through the pot with ease.

In terms of placement, full sun is best for phlox. You’ll get stronger stems and more flowers this way. That said, I’ve grown phlox in a spot that only got morning light, and it still bloomed, just with fewer flowers.

For a Barbie-pink flowering option, try this Phlox paniculata 'Volcano', with live plants available via Amazon.

Ongoing maintenance for phlox in pots

Deep watering through the spring and summer is a good idea for phlox in pots, ideally giving them a good soaking once every few days (or even every day, if the weather is extreme).

Phlox will also benefit from feeding. I tend to apply a tomato feed every couple of weeks through the summer – something like this organic tomato feed from Walmart.

You’ll also want to deadhead regularly to keep those flower stems coming. Use clean, sharp pruners to snip back spent blooms just above a leaf node. This often triggers a second flush, particularly in early fall.

Finally, make sure you support and stake your pots. As they are taller perennials, even a gentle wind can topple stems. Try these plant supports available from Amazon, which will help to keep your phlox upright in the fall.

FAQs

Do I need to repot phlox?

Yes, repot phlox every couple of years, ideally in early spring. I usually lift the plant, shake off as much old compost as possible, and repot into fresh soil with some added grit. If the roots look cramped or the center of the plant seems woody, it’s a good moment to divide the clump.

In my experience, you shouldn't need to winterize your phlox pots. They are tough and hardy, and should be able to tolerate snow and frost just fine.

That being said, you can group containers together near the house for the darker and colder months of the year. This will create a microclimate that keeps them a little warmer, ideal in colder regions.

For more patio inspiration, see our guide on how to grow hummingbird mint in pots, and fill your yard with color this year.

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