Arno KingHow to grow Siam tulips (Curcuma)

In the mid 90s, Siam tulips, cultivars of Curcuma alismatifolia and related species, hit the nurseries and garden centres. Like many people I was enchanted and soon had quite a collection of these plants. I tried to do all the right things – bright shade in a shadehouse, regular feeding and repotting every couple of years in fresh media….. But the plants declined each year and eventually gave up the ghost.

Curcuma flowers, showing their unusual structure

The genus Curcuma belongs to the ginger family (Zingiberaceae) and includes many very attractive species as well as spices such as Turmeric (Curcuma longa) and Zeodary (Curcuma zeodaria). Many of these species have broad green leaves and appreciate a semi-shaded location. They also grow well in pots in the shadehouse.

Siam tulips need full sun in subtropical climates

The Siam tulip has a thick, olive-green leaves and the plants form a cluster of stems and leaves usually 300 to 400 mm high. The flowers stand just above the leaves. The lower bracts of the inflorescence are small and green with flowers emerging between them. The top of the inflorescence has a brilliant cluster of colorful bracts that with some imagination do resemble a tulip in formation.

I put my initial lack of success with these plants down to climate. Perhaps the plants needed a more tropical environment? I found many other people had had similar experiences and after a few years these plants disappeared from the nurseries completely.

Curcuma alismaefolia or Siam tulip, with hot-pink flower bracts, resembling a tulip

Over the ensuing years, I read more and more about these plants. Coming from northern Thailand and Cambodia they actually grow in grassland in full sun. The climate is subtropical and seasonal, with a dry season lasting for at least 6 months. Last year I got to visit the natural habitat of these plants and this gave me a totally different perspective on how they might be grown in cultivation.

I was inspired and on seeing plants offered for sale decided to give them another try. This time the plants were placed in the hottest, sunniest parts of the garden – among Zephyranthes and other low grassy groundcovers. What a difference. The plants have thrived and are covered with flowers and robust new growth. I think I have finally mastered these plants!

Rich, pinky-red Curcuma flower bracts work well surrounded by dark red foliage

Early in the season, when the plants emerged from dormancy, we had exceptionally dry weather. This did not phase the plants at all. They just kept growing and were soon in full flower.

The beds where the plants are growing, have been cultivated and have a yearly topdressing of 50 to 75 mm of forest mulch. The worms have been busy working this organic matter into the soil. The fertiliser used on this garden is Nutri-store Gold (a biological fertiliser), and additional humates and zeolite have been added as I have limited water and need to ensure I have soils with a high water holding capacity. Dilute foliar sprays of fish fertiliser (Powerfeed) are applied at irregular intervals.

The only issue I now have with these plants is their flower colour. The flowers are stunning, but in shades of mauve, pink and white. I am now growing them in my ‘Sunset Borders’, which feature foliage and flowering plants in brilliant yellow, orange and red. Pastels and rich chroma colours just don’t look good together. The good news is that a garden area soon to be constructed near the house will be predominantly white and scented and this is where the plants will eventually reside. By then I hope they will have multiplied so much that I can undertake some mass plantings.

Siam tulips come in pretty pastels as well

I strongly recommend growing Siam tulips to gardeners in coastal subtropical and tropical areas (including north of Ballina on Australia’s east coast). Plants put on quite display in the garden and the flowers are well displayed and showy. The flower season is long and the plants are very attractive in habit. You may need to hunt around to find them, but hopefully more and more people will discover how easy they are to grow, if given the right location – in full sun.

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Arno King

About Arno King

Landscape architect, horticulturist, journalist and keen gardener, Arno is a regular contributor to Subtropical Gardening Magazine. Based in Brisbane, Arno grows a wide diversity of unusual plant species and has particular interests in growing edible plants in creative settings and biological and organic gardening. Brisbane, Queensland

15 thoughts on “How to grow Siam tulips (Curcuma)

  1. Diane on said:

    We bought a Siam Tulip 3 months ago – it had 2 flowers. It is in the sunniest part of our yard, just outside our screened porch. We now have 22 tulips with 3 more ready to bloom. It is beautiful and our favorite flower,

  2. Teresa Cole on said:

    I bought 2 plants in Houston putting one in a part sun/ part shade on the dry side. The other in morning sun, fairly damp. The latter mentioned, did not live long, but the former bloomed all summer, made it through a winter with a few frosts and multiplied(3) looking perfect this summer and never once drooped. I have friends waiting for me to share, but I want to wait a few years. I think the white would be nice en masses with hostas. Will try that next.

    • Arno King on said:

      Hello Teresa

      I’m glad to hear Siam Tulips do well for you in Houston.

      I find these plants like full sun to very light shade, good drainage and warm wet summers and dry winters.

      I think you are wise waiting a while before sharing plants with friends. The plants look much better in larger clumps.

      I have seen spectacular mass plantings of these plants in Thailand, particularly along roads and in parks around Bangkok. The white cultivars are particularly impressive. If people only new how long the flowers lasted and how spectacular plantings could be, I am sure they would be more widely planted.

      My gut feeling is that spring flowering hostas, that prefer cool shaded (temperate woodland) conditions and summer flowering Siam Tulips which like warm sunny (tropical grassland) conditions may not be the best of companions. However, let me know how the planting goes. I combine my plants with Zephyranthes and Habranthus lilies and Diamond Frost (Euphorbia hypericifolia). All seem to thrive in similar conditions, have complementary flowers and flower concurrently.

      Good luck with your plants.

      Arno

      • Teresa Cole on said:

        Thanks for the tip and you are probably right about the hostas ( they don’t seem to do well in Houston anyway). They are near rain lilies now and I will look up the other two you suggest. I would love to have a huge patch of both colors. If you have a photo, please post.

  3. Anton on said:

    I so enjoyed reading this, thanks Arno! I was simply overjoyed to hear of your initial failure (lol) as I was sure good news was to come, the solution to all my woes but sadly…..
    I have quite a large collection of these, both collected in Thailand itself and imported Dutch varieties. The latter whose bulbs are grown for the pot plant industry and in some strange places including South Africa. Dutch weather is not ideal for mass curcurma propagation. The “bulbs” are then shipped back to the Netherlands and grown on for sale.

    I have found much to my disappointment that many I have bought as pot plants that include some stunning varieties, look fantastic when purchased but go into rapid decline after a few weeks, then never return in the same glory they were purchased as. I cannot for the life of me figure it out. If its unstable genetics or my conditions I just dont know. Sometimes they just keep the existing flowers then keel over and the next year come back as tiny little runts. Or the flower revert to a wilder type the colour changes completely, the lovely dark purples turn to pasty pink…. the flower size change. Sometimes they put up what look like virus infected flowers with spots and deformed bract heads.

    Its so disheartening. Yes I’ve always grown these beauties in full sun, as we have very high humidity. Our winters are cool and dry, basically the perfect conditions. I have visited many farms in Thailand where they grow these as well. Im thinking it could have something to do with low temps in freight as they are flown in as fully made pot plants. This could be affecting the bulbs in some way. It must be said that some farms in Thailand battle to keep them healthy too, especially during the wet season in the Chiang Mai area. I’ve certainly seen some sad looking fields of infected flowers. Others which use heavy fungicide applications (sometimes as much as once a week) and sterile conditions bordering on hospital like conditions seem to fare much better. Planted on raised beds designed to keep splash down and drainage at a max. Unfortunately much of what was said I couldn’t understand so who knows what vital tips I missed. Im not sure which fungicide to use, some are lethal. Im not sure I even want to use fungicide at all….and certainly not at those rates or indefinitely just to keep them alive!

    The good news is that some limited jewel like varieties I brought back with me from Thailand appear to flourish, no problems at all. These have mostly been the wild forms and selections. They have small waxy flower heads in deep claret ruby, green tipped pinks and pure white. They thrive in mixed plantings and self seed in a charming manner amongst my pot plants and beds. Mostly I grow them with Arundina graminfolia but also grasses and other plants.The seed I also introduce to almost all my outdoor potted plants as they make charming surprises and reach flowering size in one year, the flowering bracts get bigger each year but not much bigger than and inch or two. A very few of the larger flowered paper whites and pinks I’ve brought back have also succeeded year after year. One particularly good one came from Queen Sirikit gardens, which I’ve also named “Queen Sirikit” as its such a lovely thing with tall thin strong flowers stems and huge wine glass shaped bracts that elegantly twist at the tips. C. roscoena also thrives, every year it puts up huge bright orange bract heads in dappled shade.

    The newer more stunning hybrids and cultivars grown also for the cut flower industry again in the Netherlands however just dont do it for me in garden conditions. I save all and any seed anyway and plant so hopefully I get some interesting results. These take three years to flowering for me and many seedlings perish along the way but what Im hoping I end up with are much healthier stronger plants. Would be nice anyway. I’ve yet to see anything as good as the original.

    I just wish these things were easier!!! I know this was posted in 2012 and its now 2016 but I hope you are still having success with them. I would be interested to know, and what still does thrive.

    Today I just couldn’t resist and I bought yet another Dutch cultivar, “Sunrise” or something, tall, almost white with bract tips dipped in raspberry red. Not getting my hopes up but we shall see.

    If you have any more secretes Im all ears! BTW they prefer slightly alkaline conditions so you need to lime if your soil is acidic or leaf mulched or they also go into decline….not that it’s helped me at all. (;

    • Arno on said:

      Hello Anton

      thanks for your comments. My apologies for taking so long to respond, Somehow I missed it.

      My plants had been growing into large clumps, but this autumn a local bird, the bush turkey, started to dig them up and eat the tubers. I will place chicken wire over them this summer and this will protect them. Until they sprout however, I’m not sure what I have left.

      The only other issue I have had in recent years is a fungal disease which shortens the life of the flower bracts and turns them brown. I have been applying added garden lime and silica (diatomaceous earth) in the hope I can build up the plant tissue rather than spraying with fungicide (and getting collateral damage by destroying soil biology).

      Thanks for the tip regarding alkaline soil. I suspected the plants liked high calcium and will ensure I keep an eye on soil pH in the future.

      You seem to have a lot of cultivars of these plants. I don’t think such a range is currently available in Australia.

      Arno

  4. Connie on said:

    My curcuma is turning brown, not the leaves the stem and flower itself. Is this normal and should I prune the brown ones off?

    • Arno on said:

      Hello Connie

      I cut the browning flower bracts off and keep the leaves below. The bracts browned for me due to a fungal disease and before this they lasted right up until the leaves turned yellow.

      I am endeavouring to reduce these impacts by liming plants (approx one handful of garden lime per square metre each year) and adding silica (diatomaceous earth) to enhance tissue structure.

      Arno

    • Arno on said:

      Hello Denise

      I try to retain the leaves on the plants as long as possible. If the flower turns brown, I cut off the flower stem but retain the leaves. As the weather cools the leaves turn yellowish and then brown. I cut them off when they are brown and dry.

      Arno

  5. Teresa Cole on said:

    I live in Houston, and I don’t cut mine back at all. ( this is my 3 rd year). They seem to just disappear like hostas when they go dormant, and new growth appears in mid June. I am certainly not an expert though.

  6. Arno on said:

    Hello Teresa

    yes I have the same experience. However being in the southern hemisphere, my plants appear in November/December.

    Arno

  7. Duane Jelinek on said:

    I had a plant in a container. The top leaves have dried so I removed the plant from the container. I “harvested” the bulbs. Should I plant them now in the Fall [now nearly mid- November in Maryland, US]? Or should I store the bulbs in a cool/dry place indoors and plant in the spring?

    • Arno King on said:

      Hello Duane

      these plants are quite tropical so it is best to leave them in the container and store them somewhere it doesn’t get too cold. Keep the media dish, but not bone dry. Plant out when the soil temperatures are above 20 degrees. In Maryland, it may be best to grow them in a pot and sink them into the garden during the warmer part of the year.

      Arno

  8. Sandra Hudson on said:

    Hello Arno
    I loved reading all the info you put out and the pictures spur me on!
    I live in Mackay FNQueensland and fell in love with this most beautiful plant and just had to have it and give it a go.
    It’s in a pot. Do you suggest that I keep in full sun in this location or shadier spot? We get no actual winter here and never frost. Many thanks Sandra

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