MW #5: Blue Dominance . . . but can it last? Traditional Cache

Middleton Woods #5: Blue Dominance . . . but can it last?

This is the 5th of a short series of 5 caches hidden in these beautiful ancient indigenous 45.8 hectare broadleaf woodlands just north of Ilkley. They join several existing caches providing additional incentive (if needed!) to visit this special place.

To Reach the Cache:

Park @ or near N 53 55.955 W 1 48.881 adjacent to Ilkley Suspension bridge and make your way into the woods where you will find myriad trails enabling you to make your way around easily.

See Gallery for a map of the woods with trails, parking spots and caches.

The appearance of vivid bluebell carpets in British woodlands is a sure and spectacular sign of spring. They are Britain’s favourite wildflower and the carpets, such as those in Middleton Woods attract many visitors.

Bluebells also form carpets without a wooded canopy – eg. on Skomer Island in Wales – and this shows the locations of ancient forests, long after the trees themselves have vanished. This is because, unlike trees, bluebells have most of their biomass and reproductive organs (the bulb) below ground where they are better protected.

But just how does the bluebell manage to be in full flower when other plants are only just starting to grow . . . ?

1) Their growth is triggered by cold: While most plants require several hours above a certain minimum temperature before they start growing again, bluebells are dormant during the heat of the summer. Instead, their seeds are triggered to germinate when the temperature drops below 10°C, allowing them to get a vital head start and be in full bloom when spring finally arrives.

2) They dig deep: Bluebells have contractile roots*, which pull the bulb deeper and deeper into the soil with every year of growth. This protects the bulb from frost, which starts from the soil surface, and temperature fluctuations, and provides better access to water in drought conditions. * These pull bulbs or corms of monocots, such as hyacinth and lily, and some taproots, such as dandelion, deeper in the soil through expanding radially and contracting longitudinally. They have a wrinkled surface.

3) They use fructans as reserve carbohydrates: While most plants use glucose and build starch or cellulose, bluebells predominantly convert sunlight into fructose, from which they build fructans. This adaptation allows them to photosynthesise at temperatures below 10°C. The plant’s large bulb comprises up to 70% fructans, which fuels their winter growth.

Fructans also minimise formation of new cells, causing existing ones to elongate instead. This is advantageous because bluebells can grow without biosynthesising all the material needed for new cells. The effects of this can be seen by examining bluebell leaves - at first they are firm and upright, but become less rigid as the cells elongate.

4) They spear through any obstacles: The leaves that emerge from the bulb are as close to each other as possible and shaped like a spear with a small, sharp tip. This lets them find their way through any obstacle – both below and above ground. When the leaves start emerging in mid-winter, there is usually a lot of dead leaf matter and other detritus lying on the forest floor. Having many little spears is critical for punching through this into the sunlight.

5) They cooperate: they cooperate with mycorrhiza – symbiotic fungi which obtain carbon from the bluebell in exchange for nutrients, particularly phosphorus. Both parties win, thanks to their use of a wood wide web.

6) They compete: Phosphorus is an important resource for plants – and bluebells 'know' it. As well as securing their supply with the help of mycorrhiza, they also restrict that available to other plants - by storing phosphorus as phytate, which can only be converted into a usable form with specialised enzymes.

7) They shape their surroundings: They engineer the soil and their environment to optimally support themselves while making it harder for other species to grow. As well as storing phosphorus and using fructans, they win the 'turf war' by carpeting the space above ground.

However English bluebells are not totally dominant . . . the Spanish Bluebell Hyacinthoides hispanica was introduced by Victorians as a garden plant. It now grows in the wild and crossbreeds with the British native bluebell to form a hybrid Hyacinthoides x massartiana (see photo below) - one of the main reasons the British bluebell is a protected species.

There are several ways to tell them apart:

Hybrid plants have the potential to eventually overtake the native species. Currently around 1 in 6 broad-leaved woodlands in the UK contain the hybrid species. Can you spot any intruders in these woods?? If so, post a photo . . .

Sheffield has a bluebell protection programme with a web page for reporting sightings which are then mapped, helping to track & control the spread of non-native plants - see Gallery.

See here for an interesting page on bluebells and Bluebell Railway Walks.