Most amateur gardeners know flame flowers primarily by their botanical genus name Phlox. The best known is the High Flame Flower (Phlox paniculata), a classic farmer’s garden perennial that belongs to summer like the sun. During the middle of the year it blooms tirelessly and colourfully, spreading its unmistakable summery scent. But the large Phlox family has many other species to offer, which find a suitable place in almost every garden. With Phlox you can create a garden that is in bloom from spring until the first frost.
The flame flowers (Phlox) are a plant genus from the family of the bulky plants (Polemoniaceae) and almost without exception originate from North America. The Siberian phlox (Phlox sibirica) is the only species that is also native to North Asia. The most popular species for the classic perennial bedding are from the river valleys of North America and are characterised by countless, mostly fragrant flowers and symmetrical inflorescences, which makes them enormously decorative. In addition to the well-known tall perennial Phlox (Phlox paniculata), there are about 60 other Phlox species, many of which are suitable for the garden. Another group are the cushion-like growing flame flowers like the cushion phlox (Phlox subulata) and the wandering phlox (Phlox stolonifera). Because of its enormous popularity, Phlox has been cultivated as a garden plant since the 18th century and the number of available varieties is now in the triple digits.
The sometimes annual (e.g. Phlox drummondii), but mostly perennial herbaceous plants come in many different varieties. From low lying creeping species (e.g. Phlox subulata) up to one meter high perennials (e.g. Phlox maculata) every growth form is represented in the Phlox family. Many species carry their flowers in large panicles on stems above opposite, simple green leaves. The colour range of Phlox concentrates on pink and pink tones, but is extended by white, purple, blue (for example Phlox paniculata ‘Blue Paradise’) and mixed flowers. The aromas of the Flame Flower range from honey-sweet scents to the scent of violets and a slightly tart herbal aroma, which the plants use to attract moths and bees in large numbers. But beware: not all Phlox species have a fragrance! In general, the intensity of the scent of Phlox flowers depends on the temperature. The strongest scent develops at the warmest time of the day, around noon or evening, depending on the location.
Location and soil
The right location for Phlox is light and airy, so that leaves and flowers can dry off quickly after a rain shower. Depending on your needs there are Phloxes for partial shade or full sun. The more sun the plants get, the more luxuriant the flowering and scent. The soil should be nutrient-rich and well-drained for species native to floodplains. Most of these specimens can cope well with damp soil, but none of them can tolerate waterlogging or persistent wet leaves. The robust large-leaved Phlox (Phlox amplifolia) tolerates drought and competition from tree roots quite well. Padded Phlox (Phlox subulata) prefers sandy soils in full sunny places. Phlox stolonifera (Wandering Phlox) is not very assertive and needs an open, loose and weedless soil in light shade.
Whether in a rockery or a colourful perennial bed, Phlox adorns every garden. The popular perennial Phlox (Phlox paniculata, also known as “High Flame Flower”) is one of the most beautiful flowering plants in a midsummer farm garden with a height of one metre and an impressive flowering in pink, violet, light blue or white. The robust, competitive and healthy large-leaf Phlox (Phlox amplifolia) is ideal for shady garden places under trees that are not well suited for Phlox paniculata varieties. The up to 170 cm tall Phlox species also thrives in drier locations and flowers persistently from July to September. Unfortunately, however, it lacks the beguiling scent with which many of the tall Phlox species enchant. For dry stone walls and rock gardens, planting with evergreen cushion phlox (Phlox subulata) is a good idea. The bright blue, pale pink or white star-shaped flowers appear on 15-centimetre high cushions of dense foliage as early as May. The 20 centimetre high wild form Phlox douglasii grows less overhanging but just as compact. Both species are also suitable for planting on slopes.
Wander-Phlox (Phlox stolonifera) is the right candidate for underplanting or garden corners in light shade. With its short runners it spreads widely along the edges of trees and under bushes. The numerous flowers are bright pink, white or blue in May and June and are fragrant even at night. The meadow phlox (Phlox maculata) scores with its huge cylindrical flower panicles and long flowering from June to August. Similar to perennial phlox, it is suitable for a sunny spot in the perennial bed. Already in April the low forest phlox (Phlox divaricata), also known as the blue phlox, begins to flower in light shade. It fills the still bare areas between late sprouting perennials with its characteristic blue but also white flowers, which seem to float gracefully above the foliage, and exudes a lovely scent.
When designing the bedding, care should be taken not to mix too many colours, especially with tall species, despite the great temptation to do so, as the Phlox flowers are very lush and the planting will then quickly appear overly gaudy, especially at a distance. A restriction to one or two colour shades, on the other hand, makes the bed appear calmer and more noble. Tip: Combine varieties with different flowering times so that you can enjoy the Phlox’s fireworks of flowers for months. The high Phlox varieties such as Perennial Phlox or Meadow Phlox, but also fragrant small Forest Phlox varieties are ideal as cut flowers for romantic bouquets.
Planting and care
Since Phlox varieties, like all perennials, are sold as container plants, they can be planted practically all year round from spring to late summer. Annuals and smaller specimens are placed in the bed in May. Phlox is usually extremely vigorous, so depending on size, the plants should be placed in the bed at a distance of 20 to 40 centimetres. Especially the species in full sunny locations like Phlox paniculata need plenty of water in summer. A layer of bark compost protects against dehydration. Regular application of compost contributes to the pompous flowering and lasting health of the perennials. As the larger Phlox cultivars in particular do not have a very long life span, it is recommended to split the perennials in spring after six to ten years (meadow Phlox already after three years) and place them in a new location.
If you cut faded umbels of Phlox in time, you can extend the flowering period. This also improves plant health. Caution: Phlox is extremely sensitive to changing weather or climate conditions. Depending on location, soil quality and weather conditions, the plants can therefore show different vitality and flowering from year to year. Allow new or replanted Phloxes three to four years to acclimatize to their new location. Especially the high cushion phlox often grows very densely and is then particularly susceptible to mildew. If you remove about a third of the shoots of well-established plants in spring, it will grow more airy and the leaves will dry out faster after rainfall.
Perennial Phlox is propagated in autumn by division. After flowering, carefully dig up the rootstock and divide it into smaller pieces with a sharp spade. After splitting, the individual pieces should be put back in another location at the same depth as before. With many other Phlox species, propagation from root cuttings works. For this purpose, five to ten centimetre long, thickly fleshed root pieces are taken from the mother plant and dug horizontally into the soil with a sand content. Keep the substrate slightly moist and new shoots will soon appear. Propagation by head cuttings is also very easy: Cut off shoot tips from the mother plant that are about 15 centimetres long, remove the lower leaves, dip the cut surface into growing soil and stick the shoot into growing soil. The shoots will take root very quickly and will be planted out as soon as the growing pot is almost rooted through.
In the wrong location, there is a risk of powdery mildew infestation, which is indicated by a white fungal lawn on the upper side of the leaves and can cause severe damage to the plants. Preventive treatments with environmentally friendly net sulphur can prevent this. In the meantime, there are also a number of varieties of the high flame flower that are relatively resistant. A typical Phlox pest is the foam cicada. It sits hidden in a drop of foam (hence the name) on the leaf and sucks on the plant. The easiest way to remove it is with a jet of water from the garden hose.
Another harmful insect is the stem nematode, also called stem larvae or nematode because of its appearance, which gets stuck in the shoots of the Phlox and cannot be controlled directly. Nematodes inhibit the uptake of water and nutrients by the plant, which causes thickening on the leaf stalks, malformations on the young leaves and partial death. Infested shoots should be cut off as deeply as possible and destroyed immediately.
Frequently asked questions
What is Phlox?
Phlox refers to a plant genus to which both annual and perennial species belong. Particularly popular are the high flame flower, the cushion phlox and the wandering phlox
What does Phlox look like?
Phlox comes in many different varieties: There are small, large, creeping, annual and perennial species. Many carry pink or pink-coloured flowers in large panicles over green leaves.
In which colours does Phlox flower?
Depending on the species and variety, the flowers can be pink, white, blue, purple or a mixed colour.
When can Phlox be planted?
Container plants can be planted from spring to late summer. In May smaller specimens and annuals can be planted in the bed.
How long does Phlox flower?
The flowering time depends on the species and variety. Some species flower as early as April, others only from July. The flowering time of Phlox can be prolonged by pruning, as Phlox belongs to the group of reassembling plants.
What goes with Phlox?
How do you maintain Phlox?
In summer Phlox should be watered sufficiently and regularly fertilized with compost. After about six to ten years it is recommended to divide the perennial.
How high does Phlox get?
Depending on the species, Phlox will grow between 10 and 150 centimetres high.
Why is my Phlox not flowering?
Phlox is quite delicate. Especially newly planted or transplanted specimens should be given a familiarization period of three to four years
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.