Summer phlox

Summer phlox, with its colourful little flower clusters, is an incredibly pretty summer flower. At the same time, it is a real toughie in the garden. It can withstand rain, wind and a little frost. Summer phlox blooms abundantly and for a long time. With its lovely scent, it attracts pollinators such as butterflies and bees.

Summer phlox – a flame from Texas

‘Phlox’ means flame. It’s a fitting name because the flowers are sometimes very colourful. They can be single-coloured or bicoloured. Today, summer phlox come in both soft and intense shades of blue, purple, pink, cream and white.

The species name ‘drummondii’ comes from the Scottish botanist Thomas Drummond. It was he who brought summer phlox to Europe from Texas in the 19th century. Summer phlox still grows wild in several North American states.

Depending on the variety, summer phlox grows to about 10-40 cm tall. It flowers from July to September – sometimes even longer into autumn and early winter.

Seeds germinate best in the dark

In southern Sweden, summer phlox can be sown directly in the garden. In the rest of the country, it is best to pre-plant. Sow the seeds indoors in March-April. Allow 12-14 weeks before planting out.

Summer phlox is dark-growing. The bed should therefore be protected from light after sowing the seeds and covered with a thin layer of soil. Do this using a piece of cardboard, dark plastic, a plate or similar. Keep moist and aerate occasionally. Leave the seeds to stand at about 18 degrees.

After 2-3 weeks, when the first leaves appear, remove the light cover. Then place the seedlings in a bright and cool place. When the seedlings are large enough to be handled, move them to separate pots filled with potting soil. Thin out the smallest plants. To get a bushier growth habit, it is a good idea to top summer phlox once before planting out.

Planting out summer phlox

When the risk of night frost is over, it’s time for the summer phlox to come out into the garden. Harden off the plants for a few days by leaving them outside for longer and longer periods. Cover them with fibre cloth for the first week. This will protect the plants from sun and wind.

Choose a sunny or semi-shady spot. Keep a distance of about 20 cm between the plants.

Summer phlox is a versatile and useful plant. Thanks to its bushy growth habit and low height, summer phlox is perfect as a border plant, in pots, hanging baskets, window boxes and rockeries. It’s resistant to wind and rain, so it can thrive in places other flowers may not be able to.

Caring for summer phlox

Summer phlox likes nutrition. Water with fertiliser once a month or so. As with all plants, summer phlox thrives if you spoil it with water. Place grass cuttings or other organic material between the plants. This will keep the moisture in the soil, smother the weeds and add extra nutrients as they decompose.

Summer phlox blooms from July onwards. Remove wilted flowers as you go. Then the plant will continue to overflow with new flowers throughout the season.

Water in case of drought, but make sure the soil is not too wet.

Summer phlox can be infested with aphids. If possible, shower the plant with a soft jet to prevent and discourage infestation. If aphids get a foothold, a soap spray can work wonders. Mix 0.5-1 dl of green soap in a litre of water and spray daily until the aphids are gone.

Summery sweet cut flower

Summer phlox is very nice to pick into bouquets. It has a lovely radiance and works well both on its own and in arrangements with other flowers. As a cut flower, summer phlox has a good shelf life. In addition, the plants become bushier if you cut off some stems from time to time.

Author: Johanna Damm

Fact-checked by Erik Hoekstra

Last updated 2022-10-14