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.

Lower growing pentas form repeated mounding shapes & the colours all blend beautifully

Lower growing pentas form repeated mounding shapes & the colours all blend beautifully

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.

Use flower snips or secateurs to cut of dead flower heads

Use flower snips or secateurs to cut of dead flower heads

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 either with a perennial cradle support, or pruning back more frequently.

Taller growing species pentas in hot pink can flop over if you don't support it or prune it regularly

Taller growing species pentas in hot pink can flop over if you don’t support it or prune it regularly

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.

Red pentas comes in both taller & lower growing forms

Red pentas comes in both taller & lower growing forms

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!

I mix various colours of pentas with variegated iresine, golden pineapple sage, colourful canna & lilly pilly in the background

I mix various colours of pentas with variegated iresine, golden pineapple sage, colourful canna & lilly pilly in the background

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Catherine Stewart

About Catherine Stewart

Award-winning garden journalist, blogger and photographer; writer for garden magazines and co-author of 'Waterwise Gardening'; landscape designer turned landscape design judge and critic; compulsive networker and lover of generally putting fingers in lots of pies. Particularly mud pies. Original creator of GardenDrum. South Coast NSW.

28 thoughts on “In praise of Pentas

  1. 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. 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.

      • HI Catherine
        My red flower pentas has scrambled through my gardenia and now stands 2.5m tall. Love it !!!! Red flowers that tall which the butterflies love 🙂

        • Hello Paul! I now have a fabulous tall white one I call ‘Whyte’s White’, named for Bill Whyte from whose Roseville (Sydney) garden it came. It flowers all year round and has grown to 1.5m tall. Perhaps it needs to scramble through something red flowering to match yours!

  3. 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.

  4. 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?

  5. Will pentas tolerate hot afternoon sun? I’ve heard they are fine with heat but I’m taking my California pentas to Arizona and the best place I have to plant them receives afternoon sun. I will start them in the winter when its not too hot, but when the summer arrives it will be over 100 at times. Do you think they will they survive? I can’t leave my pentas behind.

    • Hmmm…I’m thinking the combination of afternoon sun, 100 degrees and such low humidity might be too much for them bee. However they might soldier on, just with much smaller leaves and flowers. And what have you got to lose? Might as well give it a try. Take lots of cuttings!

  6. Could you give me some directions on how to take cuttings and grow more from my existing pentas? Ive never done it before. Where on the stem should I cut?Thanks

    • Hi Cynthia – Pentas is easy to propagate, and I think probably any part you used would strike, although the older large varieties are the fastest and most successful. Water your Pentas the night before and take the cuttings early in the morning while the stems are plump and full of moisture. I usually cut just below the third node (leaf bud) from the top of the stem, trim off any flowers and scrape a tiny bit off the stem on the side of that lowest leaf bud to expose the cambium layer underneath, which is where the new roots will develop. You can also dip the cut end in a rooting hormone gel or powder. Pentas will strike in anything from damp sand to regular potting mix and even a glass of water. If you’ve got rich organic soil I’d think you could even put them straight in the garden in a shady position and water them daily and, at this time of year, they’d strike there too!

  7. I am loving my red coloured pentas, they strike so easily. I use them as cut flowers in the house. They last forever (2 weeks) in a vase, and they usually start to grow roots, I just wait until the roots are fairly big and then pop them into a pot or a garden bed and I have more pentas growing.
    I live in Annandale in Sydney’s inner west and I would like to grow some different colours, does anyone have a nice plant that I could take a cutting from?

    • Hi Pat – Pentas loves long, sunny, warm days, so it will probably need to warm up a bit more before it will flower. Depending on which part of Texas you are in and how cold it gets at night, I’d expect blooms from late May through to maybe October.

  8. Thanks for your help on pentas, i had a hard time knowing when to trim of the spent ones I am in Florida and this is the 2nd year they have come back.

  9. I have a few Pentas and love them. We live in Brisbane and I am inundated with grubs (Green & Black) eating them they actually strip the plants, the other day I managed to collect 13 grubs off one plant so it is a daily chore to check each plant. What can I do to prevent this happening.

    • Hi Caroline – ‘grubs’ could apply to several different types of garden pests however if you are talking about caterpillars then the best solution is to spray with Dipel. It contains a bacterium that only affects caterpillars and doesn’t harm any other insects. If you’re not sure whether your grubs are caterpillars, you can send me a closeup pic at info@gardendrum.com

      • Hi Catherine

        Sorry they are caterpillars I am pretty sure they are either green or black and has a little fumy thing at the end of them. I will try Dipel and see how we go as it has become a full time check every day and I think I have them all and then the next day there are more. I can get 4-5 a day now. Thanks again for response. Cheers Caroline

    • Hi Caroline, that is a common problem here in Brisbane. They are an excellent butterfly plant for this very reason and can often be stripped over night by caterpillars. Dipel is probably the best way to stop this but you should be aware that dipel will kill all caterpillars and if you want to have butterflies you will need to tolerate some caterpillars. The other options are to plant more pentas in different parts of the garden, so that you do not leave one precious plant at risk, and it is unlikely that all will be found and stripped at once. They are very easy to grow by cutting. While it is a shock to see the plant stripped to nothing but bare stems they do usually recover quickly. It is at this recovery stage however they can be vulnerable and if they get a second attack too soon may struggle to recover. Sometimes netting the plant while it grows back helps.

      • Thank you Kate

        I do love butterflies so I guess I will have to be careful or as you say or plant more and they are so pretty that wont be hard to do. Netting is also a good idea and I thought of that especially while they are recovering but it so hard to see them stripped especially when I checked them every morning and collect the little pest. Thanks again

        • Those green and brown caterpillars are the hawk moth caterpillar so you are not depleting butterfly population by removing. Apparently no butterfly caterpillars like to eat Pentas.

  10. I have 5 pentas- nth tropics. My 2 pink ones have climbed 2 metres tall- so I tie to a tree trunk. The light pink is free standing in a fence corner & they still growing taller, maybe we have a ‘climber’ here! Wants more varieties – not enough up here- FNQld

    • Yes, E,Li, there are a few varieties of pentas that grow to 1.5m even in the cool subtropics of Sydney. I find that the white-flowering form and the dark/hot pink ones grow the tallest. Unfortunately the taller growing forms seem to be the hardest to come by, as they are rarely propagated by nurseries.

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