Amazing annuals: phlox
Easy to grow and with a delightful array of colours, annual phlox deserve more attention
Phlox are best known as herbaceous perennials, though the genus also includes woodland and rock garden plants. But here we are discussing the glorious annual Phlox drummondii. The first I ever grew were the starry-flowered ‘Twinkle Stars’ but, fortunately, this easy annual has attracted the attention of breeders and there are new strains both in mixtures and single colours. The people that brought us Surfinias also introduced Surphlox (below) but I think these disappeared without trace. I remember them being introduced and their great feature was that they were resistant to mildew, the only major problem with annual phlox, but I remember that the trial plants were spotted with the disease.
Phlox drummondii is native to Texas and the states to the east and is named after a Scotsman, Thomas Drummond (1790-1835) who collected extensively in Texas.
It is a roughly hairy, slightly sticky, annual with narrow, pointed leaves with terminal clusters of five-petalled flowers. As the plants grow they bush out and sideshoots grow from below the older flower clusters to build a plant 30cm high and wide, though cultivars vary.
The most promoted was ‘Phlox of Sheep’ in creamy, caramel colours. ‘Moody Blues’ is the one I grow most often with a range of true blue and lavender blooms. But the range of colours is extraordinary, with purple, scarlet, crimson, orange, pink and almost yellow along with bicolors and, of course, the starry-shaped ‘Twinkle’ types.
There are also doubles such as ‘Promise Peach’. But I prefer the singles. Following the success of ‘Phlox of Sheep’ there is now the puntastic ‘Birds of a Feather (Phlox together)’ in caramel and pink shades but you don’t have to be seduced by ridiculous names.
Annual phlox are often recommended for cutting and they do last well in water but the habit of the plants is branched and sprawling – ideal for the garden but not as easy to get long, straight stems. What is remarkable, apart from their beauty and diversity, is their tolerance of weather. They do well in poor summers (meaning wet) and although they benefit from deadheading, they are pretty low maintenance and they bloom for many months.
They are relatively easy to grow from seed, treated as half hardy annuals, sown in late March and planted out after the danger of frost has passed. Like so many annuals, wet, cold compost is an issue so add some extra drainage to the compost. Seedlings are straggly and rather unpromising when small and they often make one straggly stem to pinching out of the growing tip when they have four or five pairs of leaves is helpful.
Use them in pots and patio containers or in borders as edging. They prefer full sun but tolerate a little shade and they are ideal to plant under roses.
The Biking Gardener 
Never even tried it. Well, not intentionally. Phlox paniculata appeared in one of the landscapes downtown a few years ago. (There are several homes uphill from there, so such surprises are not totally uncommon.) I am told that it is ‘David’, but it grew from seed, and has been around for a few years and a few generations, so could have stopped being ‘David’ generations ago. I do not care. It is white, my favorite color, and it continues to self sow without becoming invasive. Rad!
(Of course, unlike others, it would not work well under roses.)
I have never seen Phlox paniculata self seed. ‘David’ is supposed to be resistant to mildew so it will be interesting to see if its children inherit this.
I have never noticed mildew. I was not even aware that I should expect it.
It is the most common problem with phlox here. I was hesitant to plant P. paniculata in this garden but it is so lovely I took the plunge and planted one and it started to be covered in white spots within weeks.
I did not get the opportunity to consider . . . anything about it. It just showed up, and has done well. I suppose that common diseases will become more likely when more host material becomes available.
When I lived in Upstate Ny(Syracuse) Phlox paniculata self sowed a lot for me. Upstate NY has a climate well suited to perennial garden phlox : warm summers and frigid winters. I now live in Florida. Phlox drummondii grows in large quantity along the roadsides (in association with coreopsis species ), where here it is known as “ roadside phlox”.It excels in our sandy soil. Some roadside phlox is already blooming but late April through May provides the biggest show of it.Unfortunately garden phlox will not grow here.
I wonder if I have just hoed off seedlings of P. paniculata or if the season is not long enough for it to set good seed here. What colour are the wild P. drummondii that self seed along the roadsides?
Various shades of pink and white.Much like the larger photo in your article.
Ah, thank you. Good to know what they look like in the wild.