Tulips, chill and climate change
It’s that time of year when I look through the bulb catalogues to see what’s on offer and decide whether I need to buy anything new …. but there's a problem looming
It’s that time of year when I look through the bulb catalogues to see what’s on offer and decide whether I need to buy anything new …. Its so temptingand, of course, no bulb display is complete without the majestic tulip.
But there is one fly in the ointment looming large – climate change. Just this last year we’ve had a mild yet wet winter, a very cold snap, the warmest June on record followed by a pretty so-so summer and now we are basking in summer temperatures but its mid October. None of it is good news for the tulip as you will discover.
One of the world’s best known tulip gardens, Keukenhof in Holland, is already experiencing problems. They need their displays to be ready from March and in order to have the quality of displays expected by their visitors they are planting up to 30% more bulbs than usual. There are problems too in the US. The Tulip Time Festival in Michigan is hugely popular but over the last few decades the flowering times of the tulips have advanced by several weeks and now the festivals are having to bring their dates forward too.
Worrying too is the news that the wild tulip is under threat. Last year the IUCN added more than 50 species of tulip to its Red List of Threatened Species, with half at risk of extinction. The threats come from overgrazing by livestock of their montane habitat in Central Asia, overharvesting of bulbs and climate change. As the climate warms up, the snowline is retreating but plants of course can’t simply up sticks and move to a higher slopes. To find out more check out the campaign by Flora and Fauna International and Cambridge University Botanic Garden to survey and protect wild tulip habitat (https://www.fauna-flora.org/species/wild-tulips/)
So why is chill so important?
Tulips and their relatives, the crocus and hyacinth, need a period of cold to stimulate flowering. Wild tulips are found growing in mountainous areas where winters are cold. The tulip’s development is triggered by temperature and if the winter is mild and wet, tulips simply do not perform well.
Let’s take a moment to think about the life cycle of the tulip. It takes several years for a tulip bulb to reach the flowering stage. A fat bulb ready for planting in ground consists of the mother bulb, daughter bulbs and the start of the granddaughter bulbs inside the daughter bulbs, a bit like a Russian doll. Planting is followed by root formation and then a period of ‘dormancy’ in which there are no external changes. The tulip needs a period of cold to stimulate growth of the stem and leaves and floral bud. Then in spring, the flower stem elongates and the flower bud appears. The mother bulb is used up after flowering and is replaced by a daughter bulb. Once the warm summer temperatures arrive, the leaves die back, the floral bud develops and the bulb enters dormancy again.
Temperature is key is the life cycle of the tulip. It needs warmth in summer to start developing the floral bud and a period of cold to break dormancy and trigger the growth of the stem and flower in spring. But warm springs can be problematic too. If the spring temperatures are higher than average, the quality of the flowers the following year can be adversely affected. The bulbs will be at a more advanced stage when they are harvested and put into storage and this leads to the dehydration of the flower bud. Given the warm May and June in 2023, this may affect the blooms of spring 2024.
So what can we do …. I have a few suggestions
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