Catherine StewartIn praise of Pentas

I might just be a tiny bit of a pentas fanatic. I’ve been growing them for about 20 years now, in two different gardens and there’s nothing that beats them for flowering display over most of the Sydney year. Pentas is very variable in form, so when you buy it, it’s a bit hard to tell at first whether it’s going to grow to 40cm or 1.5m. Leaf size is no indicator, but I can usually guess now by looking at the internode size – that’s the distance on the stem between where the leaves come out – with longer equalling a bigger plant.

Flowers are an umbel of little star-shaped flowers in all shades of pink, as well as white, lavender and a bi-colour. The tallest and most vigorous form I have is a hot pink, which I suspect is the species.

Pentas will grow in full sun to light, dappled shade and isn’t fussy about soil type as long as it drains OK. It is very drought hardy. When the soil is bone dry and it’s really drought-stressed you might see the flowerheads finally start to droop but by then you’ll know your whole garden is in trouble.

Pruning pentas is always a problem as there’s always flowers on it so it’s hard to make yourself give it a good haircut. But if you do you’ll be rewarded by another flush in only a week or two, so don’t let the bushes get raggedy. I cut back my smaller pentas plants all over with a cordless shear about once a month which gets rid of any dead flower heads, but I prune the taller ones with secateurs, snipping out the spent flowers and taking off maybe 20-30cm down each stem to make the plant more compact.

Pentas is what’s known as a sub-shrub, which means the bottom part gets woody but the top part stays green and flexible. This means that if you let the tall ones just keep growing upward they’ll soon flop about – a situation you can rescue with one of Margaret Cory’s fabulous perennial cradle supports, or pruning back more frequently.

Unlike most other perennials though, don’t cut them back in winter when the flowering slows down (although a pentas in Sydney will likely still have a few flowers even through the depths of winter). Pentas do grow better if they’re cut down fairly hard once a year (by about 2/3rds) but don’t do this until you see signs of new leaf burst as the weather warms up in late spring. If you cut them too early they will sulk, or even die back.

Like most plants that grow quickly and flower all the time, pentas don’t last for more than 3-4 years before they lose vigour. Cuttings taken in late summer strike quite easily, so do a few each year to keep up your supply of this wonderful plant, or get along to your local nursery to pick up a few different colours and sizes.

And the cream de la creme? Pink pentas in Sydney attracts loads of native blue-banded bees!

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7 thoughts on “In praise of Pentas

  1. Adelina on said:

    I live in the Northern Rivers region NSW – pentas are a must have in my garden. From the tiny little ones to the big shrubby ones all attracting butterflies and bees. For me the added bonus is that the wallabies don’t seem to want to eat them. All of mine have been grown from cuttings – What a great plant!

  2. bee rose on said:

    Do you know which pentas are tallest? It is by color or variety? I read somewhere that the ones with the white centers are shorter. Is that your experience? But so much confusing information listed on sizes. Thanks.

    • Ah yes, it’s difficult to know! In my experience, most of the pentas for sale in the big box stores are lower growing varieties – perhaps 30-60cm (1-2ft) tall. Smaller nurseries may have taller varieties (1-1.2m = 3-4 ft) but you often have to take cuttings yourself after finding one in an old garden. Having examined the 4 taller and 3 shorter pentas in my own garden, I can report that flower center colour is not an indicator, as I’ve got white centers on both short and tall pentas. I’d look at the internode length – that’s the distance between where the leaf buds come out of the stem. On the taller varieties, it’s around 8cm (3″) and on the shorter ones, more like 3cm (1″). But of course even this will vary if they’ve been in a shady spot.

  3. bee rose on said:

    Thanks for all your great info on pentas. I appreciate it.

  4. Thanks for the info. I have a pink one and love the way it flowers constantly, and as you say, can survive quite scorching days that ” do in” other plants. They are not that common in nurseries I find, or on line, and I would love a purple one! Just read your piece in garden drum about pink being so unfashionable. Not in my garden. Enjoy your articles. Thanks.

    • Hi Evelyn,
      My pleasure! So glad to hear you enjoy the Garden Drum articles. It’s a labour of love for many of our authors including myself.
      It’s such a tough plant. Your right though, many nurseries would have to order some in as they are not always readily available.
      A lot of the time plants in stock are dependant on public demand. Hence way they always have Magnolia, Gardenia & Jasmine just to name a few.

  5. Julie Burgess on said:

    My mother always grew pentas and I struck 12 different colours. Unfortunately in Brisbane, we have a striped grub that chews the plant back to nothing in late autumn and as this is a bad time to prune pentas, many of my plants died last year. I have been trying to source new ones but nurseries don’t seem to stock them so I have been begging cuttings from people that I don’t even know. I still can’t find the dark purple and pink variety. Any suggestions as to where I can get them?

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