I’d already decided to follow changes throughout this year at the university botanic gardens when I heard of the tragic and untimely death of Mike Hughes, the head gardener, on a New Year’s Day run. Mike has been a friend and much valued colleague to many in the Department of Biosciences (and previously the Botany department) for many years so I see this partly as an extended tribute to Mike’s work. He nurtured strong links between the department and the gardens, encouraging those of us teaching plant science and some of our students to borrow plant materials, from tiny orchid seeds to fierce-looking cacti and carnivorous plants, to use as props. Mike hosted many outreach activities for both children and adults over the years, highlighting some of the fascinating properties of plants of which so many people are unaware. Recently, he supported the development of research plots to show people the kind of plant-based research going on in the department of Biosciences, from how to stop tree roots from growing into drainage pipes and blocking them to the impacts on local environments of invasive plant species.
During the Covid pandemic, Mike produced his own blog of notes and photos from the gardens to keep the volunteer ‘Friends of the Botanic Gardens’ in touch with what was happening, for 300 days after the gardens had to close to the public on 18th March 2020 – see The Friends of Durham University Botanic Garden (friendsofdurhambotanicgarden.org.uk). When the university re-opened the outdoor parts of the gardens for staff and students in January 2021, many of us appreciated the opportunity to meet up in small groups outdoors in such a beautiful place, enjoying the now well-documented mental health benefits of being out in a natural environment again.
January is not the most obvious time to be out in a garden but there is always something to see. The first time I visited, in the middle of the month, it was all about frost-rimed leaves.
A week or so later, on a bright day already feeling a little like spring, the first flowers have started to appear. Male Hazel catkins are shedding clouds of dusty yellow pollen in the slight breeze and, when I look carefully, I see red female flowers like miniature sea anemones on the same plants, each no more than a couple of millimetres across. Using the digital microscope I can see bright yellow grains of pollen stuck to the tiny red tentacles too. At least one has a stumpy pollen tube growing from it, which will carry the male gametes to the egg cells at the base of the female flowers and fertilize them.
Many trees and shrubs which flower early in the year depend on the wind for pollination so the flowers tend not to be ‘showy’ – they have no need to attract insects. Instead they rely on producing vast amounts of very light pollen, which can be transported from male to female flowers. Though hazel catkins are very conspicuous at this time of year, the flowers of many of our native trees go largely unnoticed, apart from when we park underneath one and come back to find our car covered in lots of sticky pollen! Other spring flowering shubs, like the Sarcococca (or Sweet box) which I can smell before I see, do use insects for pollination. Given that insects are few and far between at this time of year, it makes sense for the plants to advertise their presence far and wide using scent rather than more localised visual cues.
It’s not just trees and shrubs which flower early, though. Although the snowdrops, which we think of as the first plants to flower are still in bud, a few native primroses are out, along with Hellebores in delicate pinks and creamy white.
The buttercup family, to which Hellebores belong, are often regarded as primitive flowering plants. Hellebores’ large, coloured, long-lasting ‘flowers’ are actually composed of relatively tough sepals rather than delicate petals and, in the centre, dense rings of pollen-bearing anthers surround a cluster of individual carpels. The large, open flowers provide easy landing platforms for a wide range of insects – it doesn’t do for a flower to be too fussy about its pollinators at this time of year. Nectar collecting under small flaps at the base of each sepal provides the necessary incentive for visitors and markings on the sepals known as nectar guides act like insect landing lights. The anthers are held on short, stiff stamens which deposit pollen on the body of any insect crawling across the flower in search of a sweet treat. Pollen is shed before the cluster of stigmas in the centre of the flower become receptive, to minimise the chance of ovules being fertilised by pollen from the same flower – one of the standard ways in which plants maintain their genetic diversity.
Primulas such as our native Primula vulgaris have a rather different strategy to avoid self-pollination – more on this on another fascinating blog – Plant scientist.