How do I grow Polianthes?

Plantsman Geoff Stebbings explains how to get the best from polianthes, also known as tuberose

Tuberose
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Plant names can be confusing. This plant is known by a variety of names including Hawaiian garland flower, kupaloke in Hawaii and more commonly as tuberose. Polianthes tuberosa is an amazing plant, it’s a native of Mexico that is grown around the world, particularly in tropical and subtropical regions. Although the actual plant is not particularly attractive, with plain green, strappy leaves and the flowers are not large, it is the wonderful fragrance of the blooms, especially at night, that is the main reason for growing it.

Heady scent

Polianthes tuberosa in the garden

This is a plant that has been valued for centuries and the most common form is the gorgeous double ‘The Pearl’. The pure white, waxy flowers open in pairs along the stems. A single stem will perfume a patio in the evening and once half the flowers on the spike have opened I always cut the stem so that I can enjoy the scent indoors. It is rich and sweet and rather heavy – perhaps too much for some, but I love gardenias and Oriental lilies and I wallow in the heady, tropical scent!

Tender loving care

Unfortunately you can’t just plonk the ‘bulbs’ in the garden and expect success. They need a bit of TLC to get them started. I’ve been growing them for years and this is what I do:

As early as possible (March is good) I pot them into small pots. I put them so the top half of the bulb is exposed above the compost and use a good multipurpose compost. I put them in pots that are about 7cm in diameter. I give them a gentle watering and then they go into a heated propagator. If you don’t have one, then a windowsill in a sunny spot, ideally above a radiator, is fine. There is no need to put a lid on the propagator or to put a bag over them – they like warmth and air and not excess humidity. In fact I water them very sparingly until they start to sprout, allowing the compost to dry out before watering again. You should see signs of growth after a few weeks, depending on how warm they are.

Once the leaves are about 15cm high there should be roots showing through the base of the pot and now they are ready for moving into a bigger pot. This should be a few months after potting, possibly in May.

Tuberose

I then pot them into pots 10-12cm in diameter or three into a larger 15-18cm pot. Make sure they are moist before you pot them on, water them in and keep them in a bright, warm place. If they are kept too dark the leaves will be floppy. By the end of May, depending on where you garden, frosts should be a thing of the past and you can put your plants outside. Avoid, cold, windy places – a sheltered patio is ideal or if you have a sunny conservatory that will do nicely. Remember that this is a plant from Mexico and is grown by the million in places as diverse, and warm, as India and Hawaii. Depending on the weather and your care, each plant will soon produce a slender stem and those extraordinary flowers that will transform warm summer evenings into a tropical paradise.

Plants for free

Remember that polianthes is not a hardy plant and it is not a true bulb either. It can be evergreen in frost-free climates and bloom throughout summer, but in the UK we consider ourselves lucky to get flowers in late summer.

When you buy a ‘bulb’ it will have been dried and stored for some time and it will take a while to get it started again. But once it is growing, things are simple enough. Each ‘bulb’ will produce a single flower stem and then it will die. But by the time it flowers it will have produced some offsets at the base and these will eventually reach flowering size. So while you planted a single ‘bulb’ to start with, by the end of summer you will have a cluster of shoots at the base. Some people simply discard these and start again with fresh, flowering sized ‘bulbs’ the next year. But if you have a bright frost-free spot you can keep the clumps growing and, with care, these will bloom the following year.

Geoff Stebbings

About Geoff Stebbings

Geoff Stebbings trained at the Royal Botanic Gardens, Kew and has worked in magazines and gardens ever since, solving gardeners' problems. He currently writes and works in Ireland where he is building a new house and creating a garden from scratch. You can see his progress at his blog www.thebikinggardener.com
View all posts by Geoff Stebbings.