I always try to ensure that early autumn is always welcomed by the heady scent of tuberose (Polianthes). It is a bit of an extravagance but I love the overpowering perfume and, when I see the first buds open on my carefully nurtured plants I wish, for a moment, that I lived in those tropical areas where the plants presumably bloom all year and the opening blooms are picked and made into necklaces. But, for those of us living in colder areas, with winter frosts, tuberose is a bit of a laborious treat. I will describe the plant and the appeal of it and then how I grow them – because I am often asked what to do with the strange ‘bulbs’.
Tuberose (Polianthes tuberosa) is native to Mexico and was cultivated by Aztecs. It is now cultivated throughout the world, as an ornamental but also for perfumery. The wild plant, which is not known in the wild, has six tepals but, in cultivation it is represented by the double-flowered ‘The Pearl’. Having said that I have grown plants with single flowers though whether these were just reversions or weak plants that hadn’t got the energy to ‘double’ I am not sure. I have to admit that tuberose are not lovely plants. They form rosettes of narrow leaves and from the centre send up a spike of flowers, in pairs, roughly a dozen on average plants, but there can be more or fewer. Once the ‘bulb’ has bloomed it will die but will produce a number of shoots from the base that will grow until they reach flowering time.
Because these are not true bulbs but fleshy ‘shoots’ they look really rough when they arrive in the post or in packs. They need warmth to make them grow and take about four or five months to bloom after planting. In the early stages, when they have to be coaxed to grow, they need warmth and very careful watering. Cold and wet will kill them. So I plant them in cell trays, in a mix of compost and perlite, with only the corky base in the soil and the dried leaves exposed, and keep them as warm as I can. For a month or more it looks as though nothing is going to happen but eventually a tuft of green appears from the centre and you know all is well. Continue to water carefully and when the leaves are about 15cm long I repot them, three per 12cm pot, in a good compost and water more frequently.
Unfortunately not all will flower. A few fail to sprout. A few never seem to have a central shoot, but a mass of smaller offsets and these will not bloom. The offsets need to grow on for a year or more before they are big enough to bloom.
So you have to take the plunge and buy at least three to be sure of blooms. But those waxy flowers are worth every effort. They have a rich, heady perfume that, to my mind, is tropical. It does not have the sweet delicacy of sweet peas or pinks. It is heavy and cloying and almost suffocating – and I love to wallow in it. As I write, in the evening, a pot with just two flowers is pumping out its perfume into the sitting room.
After flowering the general advice is to throw the bulbs away. But you can keep them. Dry them off and keep them frost-free in winter and they can be planted the next year. If you can keep them in light and warmth you can keep them growing and the more you feed them the quicker they will come into bloom.
I need to add two more comments. Some incredible, coloured hybrids have been bred and, once again, I am trying them, so I should be posting on them soon.
Guess what! Despite being cultivated for thousands of years, and having been in cultivation in Europe since at least the 17th century (Marie Antoinette liked tuberose) the name has just changed. It has long been in the agave family – very sensible – but now it is an agave! It is Agave amica. At least it will stop the confusion of polianthes with polyanthus!