Cambridge Botanic Garden at 175 Years

Last week I volunteered as a “Science Explainer” for the 175^th Anniversary celebration of the Cambridge University Botanic Garden. I wore a bright (bright) orange T-shirt and lanyard and smiled at people as they walked by the chalk grassland and fen displays, trying to judge if they would be open to a chat about native Cambridgeshire ecology. I pointed out the pale brown newts wriggling between lily pads in the fen pond to children scampering over the fen boardwalk, explained how alkaline chalk determines what can grow in chalk soil and chalk-drained fens, apologized for not knowing where to get the next stamp on the Mystery History trail, and chatted about pasqueflowers and orchids. When there was no one around I watched bees on the meadowsweet and listened to the live music filtering through the trees and clashing with the one-man band (the “Pramdemonium”) wheeling around the Garden with bubbles coming out the horns. Festive, to say the least.

Whether or not passersby fully caught on to the reasons for the festivity, the celebration is justified—the Garden has been a dynamic center of botanical science, beauty, and public engagement for a good long while now, thanks to visionary and determined botanists and teachers. And how happy that people can gather here with music, food, kids, and curiosity again after last year’s hiatus!

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I gave a brief overview of the Garden in this winter post, waiting for summer foliage—and little did I know it then, for training as a volunteer—to do a more in-depth tour. Since most people around my volunteer post were either chasing children or mainly interested in ambling through, I only got to share tidbits from the Botanic Garden knowledge I absorbed in preparation for the event. So, lucky you, you’ll get to read it here now!

Beginnings

The current iteration of the Botanic Garden was inaugurated in (quick, do the math) 1846 when the University’s vice chancellor planted a lime/linden tree in a cornfield on Trumpington Road. Eventually, this entrance would be graced by the transplanted iron gates of the first botanic garden in Cambridge, a modest Physic (medicinal) garden planted in the 1760s the center of Cambridge, which is now entirely concrete (and happens to be the site of today’s David Attenborough Building, where I work outside of pandemic times). When the eminent botanist and eventual Darwin-mentor John Henslow ascended the Botany Professorship in 1825, botany had begun to take off as a science beyond the bounds of traditional medicinal plants. He pushed for a new Botanic Garden site with room for trees and broader visions. The University agreed, but, probably in typical fashion, bought land where people were already living, and some tenants refused to leave for another dozen years. (Meanwhile, Henslow sent Charles Darwin off on the voyage of the Beagle.) Eventually, plans went ahead, and the first Curator, Andrew Murray, took charge of the design.

 Depending on which entrance you come through, you’ll see a two very different halves of the Garden. My station in the “Ecological area” is part of the 20^th-century extension to the Garden, developed after a generous fund was set up in the 1950s, with a flexible, modular design suited for a mosaic of exhibition plots and experiments. You’ll see this from the Station Road entrance, where almost the first thing you see are research facilities and experimental beds. If, on the other hand, you come through Brookside entrance, where Hobson’s Conduit is flowing by and the Garden shop occupies an old Regency era house, you’ll set off on a curving path that loops around and through a grand garden in four sections lined with enormous trees. This half of the Garden hasn’t changed drastically from Andrew Murray’s original 19^th-century design.

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Main Walk

One difference from the historical Garden is that the grand gates where the first lime tree was planted are no longer used as an entrance. So the central avenue, called the Main Walk, doesn’t play its intended sweeping role of introducing visitors to the Garden. Once you stumble on it, though, it feels like you’re stepping into a garden made for significantly larger people. Towering over the broad path and expansive lawn are massive 160-year-old redwoods, pines, and cedars. The redwoods, Sequoiadendron giganteum, are the offspring of the beloved giant sequoias I grew up visiting in Calaveras County, California—they’re nowhere near as huge as the trees with tunnels through them, but are imposing nevertheless.  One of Henslow’s main botanical interests was the variation of individuals within a species or between species, so several species of cedars and subspecies of black pine were collected from a range of regions and planted alongside each other to contrast spreading with upright, dense needles with long needles. This kind of pattern was, of course, central to Darwin’s conception of evolution and natural selection; he evidently absorbed that awareness from Henslow.

The walk leads to an elegant fountain with stands of rushes and lily pads growing in its outer ring. The walk may have continued on into the second half of the Garden, but due to lack of funds that area remained allotment gardens for a century, and in the meantime a Director’s house was built just beyond the fountain, blocking the extension of the central design—hence the contrast between the two halves of the modern Garden.

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Main Lawn and Glasshouses

The fountain looks over the edge of the Main Lawn, which is the nexus of the cheery community gatherings like the one I volunteered at today. Room for a stage for live music, people sitting on blankets, food trucks, pavilions. In one corner is a magnificent flowering cherry tree like a goddess of spring come March. Right now, in July, the bee borders are exploding with color—the razziest, jazziest blues and the warmest purples and happiest pinks—and the bees agree.

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On the other side of the bee borders are the glasshouses, built of historical Burmese teak (no longer an option, so restoration work has repurposed teak from deconstructed buildings) and crammed with exotic tropical, desert, and alpine plants, all of them eye candy and evolutionary wonders. In one wing there are cacti of all shapes and sizes, including one that climbs like a vine and only flowers for 12 hours overnight; a towering agave that waits decades to flower and then dies; giant lily pads the size of coffee tables; whole trees (one with with stegosaurus spikes bulging from the trunk); a stunning curtain of dangling scarlet and gold flowers; exquisite jade vine; pitcher plants.

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At the other corner of the Main Lawn, the New Zealand Terrace Garden is hidden away—I highlighted it in the winter post. Many of the plants are evergreen but it’s fun to stop by in the summer and see what surprising flowers have appeared on spindly green branches or my friendly hebes.

Pond and Rock Garden

The next quadrant of the Garden is filled with a pond fed by a channel from Hobson’s Conduit—featuring willows, woodland, bog plants like the giant rhubarb—and an elaborate rock garden. The rock garden was built in the 1950s from limestone quarried in Cumbria, and apparently brought with it a snail species otherwise found only in those Cumbria habitats but living quite happily in this rock garden. The limestone slabs and terraces (which would now never be taken from their endangered habitats) are the backdrop for an impressive range of alpine and rock-loving plants, which apparently takes a lot of coaxing to maintain. These low-growing creeping and cushion plants can swing it in the harsh alpine zone, but lowland warmth, crowding, and maybe the wrong kind of soil microbes are a different kind of challenge.

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Woodlands

Another quadrant is dappled with woodland trees and semi-wild undergrowth. I’ve spent less time over here but drooled over the forsythia borders in March; I also learned about a special grove of rowan trees, genus Sorbus, with several species endemic to the UK, one only found on particular islands in Scotland. We trampled all over the long grass under those trees during another education event I helped with, checking the IUCN Red List status on the various species. Elsewhere there’s also a hefty, low-crowned tree called an ironwood which can graft its own branches to its trunk as reinforcement. The crowning jewel of the woodlands is a huge oak tree known as the Cambridge Oak, but which is given a wide berth by a wooden fence due to its aging, fungus-weakened limbs that threaten to fall.

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Systematic Beds

This is one of my favorite spots in the Garden, for purely nerdy reasons. “Systematics” refers to the grouping of plants by similarity into classification ranks like genera (plural of genus) and families. Although systematics predated the new understanding of evolution that Darwin and others were still on their way to delivering when the Systematic Beds were designed, they still tell the story of evolution. And ever since I took a Plant Classification course as an undergrad, I’ve been captivated by the idea of plant families and the diagnostic features that gather species together on the evolutionary tree. I love knowing that the rose family, Rosaceae, includes not just roses, but apples and cherries and meadowsweet, because look at their five petals, look at rose hips and apples with the many stamens still fringing the end of the fruit where the petals fell away—that’s shared ancestry. I love knowing that peas and broad beans and clover and wisteria, with their winged petals and pod-fruit and nitrogen-fixing roots, go together in the legume family, Fabaceae. Sunflowers, daisies, coneflowers, and 32,000 more species with composite flowers in Asteraceae. It’s a storyline: how plants wandered and exploded through evolutionary time. And it’s a memory palace: a framework for lodging the vast variety of plant diversity in your mind, or at least the general sweep of it.

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Andrew Murray, the first curator, wanted to display that sweep in plant beds. Systematic beds had been done in other gardens, but they were often homogenous geometrical rows. His genius was to follow a “gardenesque” design like the rest of the Garden, with rounded, irregular beds woven through the plot, each bed exhibiting plants from the same family. So you can wander through the neat ellipsoids and admire succulents from Crassulaceae, aromatic lavender and mint from Lamiaceae, tomatoes and nightshade in Solanaceae. You can compare the central section of monocots, with their parallel-veined leaves (grass, corn, rice), with the eudicots in the rest of the beds. The design is meant to facilitate teaching as well as enjoying, and though it hasn’t generally changed since Murray set it up, plant systematics don’t stay static—new information, such as DNA, and new arguments from botanists lead to (sometimes controversial) reassignments of species and revisions of entire families. So plants have been moved around in the beds to mostly reflect modern botany.

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Another modern touch is a beautiful interpretative exhibit called the “Rising Path,” a curved ramp marking milestones in plant evolutionary history—leaving the water, evolving veins, then seeds and cones, then flowers and fruit—and ending with a view of the systematic beds. The ramp tells a higher-level view of the story, highlighting the innovations that set mosses apart from ferns, from conifers, from flowering plants. But it’s the same story that’s told by the stamens of roses and apples and the pods of beans and clovers, and by all the plants in the curvaceous systematic beds.

Eastern Extension

Like I mentioned at the start of the post, I was posted by the Ecological display, one of the mosaic of gardens within the 20^th-century extension of the Garden. This mound of chalk and limestone was planted with native British plants in the 1960s and managed like a natural ecosystem, though it’s gotten somewhat overgrown since then. Next door, the fen display was put in in 2004, gradating from open water to reedbeds to willow woodland (this succession is apparently called a hydrosere). There are only four reserves still resembling this habitat that used to cover most of East Anglia.

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I won’t detail all the other charming plots in this half of the Garden in this post, though you can read about the stunning Winter Garden and about the wild chalk grasslands that the Ecological display (my volunteer station) was meant to replicate (it was even partly made up of chalk soil and seedbank from Devil’s Dyke). I’ve also been charmed by the rainbow of flowers in the Pigment Garden and the poppies in the Rose Garden, daffodils in the Fairway, Euphorbia in the Dry Garden.

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As mentioned, this area is also where research is focused. The Garden is a wonderful horticultural display, but it is much more than that. I chatted with other student volunteers who had come straight from running their experiments at the nearby Plant Growth Facility; others studying plant genetics are based at the Sainsbury Lab onsite; a labmate of mine based her Master’s project on comparing John Henslow’s plant specimens in the Herbarium to modern collections of rare chalk grassland plants. There are displays throughout the Garden detailing the ways the plants here support research on crop genetics, plant circadian rhythms, petal pigments. There are leaflets for interpretive trails through the Garden centered on climate change, another on DNA, another on plant-inspired technology.

On top of all this, there are celebrations of illustrious Garden history with free tours, Science Explainers, and stations where kids can make flower bouquets crowned with paper cutouts of John Henslow’s face. And before you leave, you can watch bees forage in brilliant yellow flowers taller than you. What a marvelous place.

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