The University of Oxford Botanic Garden News - Harcourt Arboretum

6 Botanic Garden News | No. 77Recent developments at theUniversity of Oxford Botanic Gardenand Harcourt ArboretumbyTimothyWalkerThe Botanic GardenHardy CollectionThe first frost came in the middle of October2010 and the dahlias were no more. Theautumn was earlier than in the past fewyears, and short but quite spectacular;by the middle of November the Gardenwas looking very sad and ready to be putto bed. On the morning of Friday 17thDecember the sky over St Hilda’s Collegewas an ominous bright red, reminiscent ofJanuary 4th nearly 12 months earlier. It wasobserved that 36 hours after that Januarysunrise we were knee-deep in snow andsure enough by lunch time on December18th, 20cm of the wretched white stuff wascovering the Botanic Garden.In the subsequent week the airtemperature fell to –140C and the snowremained. The evergreen plants stickingup above it started to suffer. Cistus andcoronillas were looking miserable, exceptfor their lower 200mm. I assumed thatThe Garden under heavy snow,December 2010those plants covered in the ‘blanket’ werefine and this hypothesis was tested when itcame to harvesting vegetables from our ownplot for Christmas dinner. It was discoveredthat, sure enough, the soil was not frozenand the carrots and parsnips were easilypulled, in contrast to the year before whenan axe was required.The list of plants flowering on January1st was shorter than usual even thoughthe snow had melted. The Hamamelismollis, which is normally a sure bet to beflowering on Christmas day, did not reallystart its display of colour and scent untilthe middle of January. Despite the advicein many gardening books, you can growHamamelis on alkaline soils. The criticalfeature for successful cultivation appearsto be a moisture-retentive soil in the plant’sformative years before it has grown rootsdown to the water table. The Chimonanthuspraecox was also flowering well by themiddle of January along with Viburnum xbodnantense ‘Dawn’, Jasminum nudiflorum‘Seiboldianum’, and Lonicera x purpusii.In a strong cast of smelly plants thewinner must be Sarcococca confusa. This isa Top 10 plant if ever there was. The scentengulfs you like a blanket and is completelyout of proportion with the size of theflowers. Only the male flowers producenectar but it is not clear whether both sexesproduce scent. The other incongruousfeature of this species is the simultaneousflowering and fruiting; the black berries arein fabulous contrast to the white flowers.There must be a reason why the plant delaysChimonanthus praecoxthe development of its fruit for twelvemonths; possibly because the release ofseeds in the summer would coincide withdry conditions in its native China.There were eleven species ofSarcococca at the last count (in 1986)growing from Afghanistan to Chinaand into the Philippines. Their leavesall resemble those of Ruscus aculeatus(Butchers’ broom), especially the leavesof Sarcococca ruscifolia, though the leavesof the Ruscus are not leaves – they arephylloclades (from the Greek phyllo =leaves and klados = branch). So when isa leaf not a leaf? When there are flowersgrowing from it. In Ruscus the flowersappear to be growing from the centreof the leaves, which means that theleaves are in fact stems or branches thatresemble leaves. The leaves are presentbut in Ruscus aculeatus they are thesmall brown structures at the base of theflowers. The leaves of Ruscus hypoglossumare much more clearly visible.Hamamelis mollisRuscus aculeatusLeaves come in many different shapesand sizes and with many more functionsthan just photosynthesis. A new secondyearundergraduate practical class tookplace in the Garden in late October in whichthe students had to inspect sixty differentspecies and to comment on the leaves,their morphology and function. The resultof this work is that the students now knowthat a leaf is a structure at the base of a bud(subtending the bud to be precise) and thefunction is immaterial.