Friday, 24 August 2012

Keeping it in the family...

Towards the end of summer there is one plant family above all others that provides the final foray of colour, the daisy family: Asteraceae.

There are c. 27,000 species in this family assigned to 1,765 genera, making it one of the largest plant families. The diversity of this group is pretty staggering, with representatives found worldwide, only absent from the Antarctic mainland.  From annual herbs and arctic alpines to the narrowly endemic and threatened, arborescent Dendroceris of Chile.

We represent a reasonable amount of this diversity at the Botanic Garden, both in the Glasshouses and the Gardens. Here are a few:

Rudbeckia maxima
Rudbeckia maxima from the central and southern USA is a fine garden plant. It grows to about 1.8m, has sumptuous, glaucous, ornamental leaves and does not need staking. Grown as a repeated element through plantings it provides a very natural effect.

Dahlia 'Moonfire'
The Dahlias are now in full bloom, somewhat delayed by the weather. We cultivate a large number of cultivars at the Garden, mostly within the Autumn   Border. These are bedded out each June, following on from the spring flowering tulips and forget-me-nots. They are then lifted in late October and the tubers protected over winter in deep frames in the nursery. The best of the bunch include: 'David Howard', 'Moonfire' (right), 'Grenadier', 'Twinings White Chocolate' and 'Dovegrove'.

Bartlettina sordida
The Glasshouses hold a range of interesting species. Including the spiny shrub Barnedesia caryophylla from South America, Bartlettena sordida (left) from Mexico, which is vaguely reminiscent of Eupatorium and the endangered Centaurea akamantis from Cyprus.
Centaurea akamantis

As well as all these striking ornamental members of the family, it's also worth mentioning that many of them are familiar and important food crops. Both kinds of artichoke, Jerusalem (Helianthus tuberosus) and Globe (Cynara cardunculus var. scolymus) are in this family. The former has edible tubers containing inulin, broken down by bacteria in our large intestines yielding the familiar and rather antisocial side effects of eating these tubers!

Globe artichoke

Pop into the Botanic Garden over the next few weeks to see this family at its best.

Thursday, 16 August 2012

Plotting on...

This year's curious weather has not been too kind to the vegetable plot. Unseasonal warmth and drought followed by months of cold rain... Most vegetables are annuals or are at least grown as such, and they need good conditions to establish themselves. Bad weather at the wrong moment can set crops back to the extent that they never really establish well. Perennials, on the other hand, can endure difficult conditions and even thrive in them- our rhubarb is a good example.

Courgette and sweetcorn bulking up.

Broccoli 'Beaumont'

Nevertheless, the vegetable plots  are producing. Last week the first brassicas were ready: cauliflower, calabrese and 'Hispi' cabbage were all harvested by Oxford Food Bank as part of their weekly collection. Courgettes, which had refused to grow in the cooler temperatures, finally began to bear fruit and the first french beans developed from the subtle pink flowers of 'Cobra'.
         Climbing French Bean 'Cobra'
It has been exciting to watch the onions bulking up since the days began to shorten after the summer solstice. This decrease in daylight length is the trigger for seed-grown onions to put all their growth into bulb formation. We sowed pinches of onion seed in modules at the beginning of february and planted out the whole modules. As they have grown the onions have just pushed each other apart. The drooping, yellowing tops are a sign that they will soon be ready to harvest!

Onion 'Ailsa Craig'
We have had to wait longer than expected for the potatoes to reach a worthwhile size- 'British Queen' is a second early and 'Anya' is grown as a maincrop, we get good results from harvesting it earlier and although the potatoes are smaller we can usually harvest before blight affects the plants. This year the humid conditions have caused some blight- in an attempt to save the crop we have removed all the foliage to ground level to avoid spores being washed off the foliage into the ground. So far, so good...

'British Queen' before losing her foliage to blight.

Friday, 10 August 2012

Giant water lilies, scarab beetles and sublime aquatics..

The Lily Tank in the Lily House is burgeoning and looking suitably exotic this week. The star of the show is the giant water lily, Victoria cruziana, which is in flower for the second time this year. This plant hails from South America and produces enormous floating leaves up to to 2.5m across. We grow it as an annual plant, sowing the pea-sized seeds in February and then plant out in the Lily Tank in April. The flowers open at night (or late in the day), each one lasting only two days. 

Victoria cruziana
On the first night of opening the flower is a pure white, this attracts the scarab beetle pollinator (Cylocephata castaneal) in the wild. At this point the female organs of the flower are receptive to pollen, but the flower's own male organs are not yet active. On the second night the flower changes to a pink-plum colour. At this stage the female organs are no longer receptive, but the male anthers are shedding pollen in abundance. In the wild the night flying beetle enters the flower on the first night, feeds on nectar through the day and then escapes on the second night covered in pollen. The beetle then visits another white flower promoting cross pollination.

Noah Walker at 10 weeks

There are many stories telling of floating young children on these leaves, we thought an experiment was required to test the theories. Back in 2001 new born Noah Walker, son of our Director Timothy Walker, was happily floated on one of the Victoria leaves. This made headline news in the Oxford Mail and prompted renewed interest in this tropical behemoth.

Noah Walker, August 2008
Some seven years later the question "just how much weight can a leaf support" was posed. Once again Noah willingly found himself the guinea pig. On a warm August day in 2008 Noah was again successfully floated on the leaf of Victoria.
Not wanting to stop there, Jonah, Noah's older brother, volunteered his services. Unfortunately on this occasion Jonah sank. So, in conclusion, the optimum load bearing capacity is somewhere between the weight of a seven and nine year old.

Nymphaea x daubenyana

Other plants of interest in the Lily Tank include Nymphaea x daubenyana, a hybrid that arose in this tank in 1874 and named in honour of Professor Charles Daubeny, a previous keeper of the Botanic Garden who installed the tank in 1851. Oryza sativa, cultivated rice, is grown along the margins, a plant that sustains 50% of the World's population as a staple food crop. A large stand of papyrus reed, Cyperus papyrus, occupies one corner of the tank. This is the plant used by the ancient Egyptians to manufacture papyrus parchment paper. Once common along the River Nile, it is now largely absent due to competition from invasive species.

Oryza sativa

Come down to the Botanic Garden and take a look for yourself. If you are in luck you might catch Victoria in flower.

Thursday, 2 August 2012

Olympic aspirations...

James inspecting germination
In November 2011 Professor James Hitchmough arrived at the Botanic Garden to conduct the first of the sowings on the new Merton Borders. This week he returned to check on the progress.

We contacted James in early 2011, hoping that he would be interested in working with the Botanic Garden to establish sustainable plantings within the framework of Kim Wilkie's master plan for the Lower Garden. Much to our excitement James was eager to be involved. The timing could not have been better, with James designing and implementing schemes to wow the global audience at the Olympic Park this summer.

James visited the Garden and discussed his ideas, a concept followed along with a design. It was all very exciting and new, a great direction for the Botanic Garden to be taking. Our aim was to communicate alternative approaches to gardening, with the emphasis on sustainable development.

Eremurus stenophyllus

James' research focuses on producing highly ornamental, yet sustainable, naturalist plantings, based on the study of natural plant communities in the wild through the direct sowing of seed.

Seasonally dry grassland communities from three bio-geographic regions of the world are represented in the planting at the Botanic Garden:
Agapanthus 'Headbourne Hybrids'
            • The Central and Southern Plains of the USA
            • High altitude areas of Eastern South Africa
            • Southern Europe to Turkey and across Asia to Southern Siberia

Once established the new borders will be transformed into a sustainable, dry (non-irrigated), highly ornamental planting. Our aim is to showcase plants that will become more important in the future if climate change models prove to be accurate. Over 100 species make up the planting palette, 85% of which are being established by the direct sowing of seed.

Oenothera macrocarpa var. incana
The seasons have been challenging, but seed has germinated well and we are now seeing the first flowering. James is confident that the display next year will be fantastic, and in a year or two can perhaps rival his plantings at the Olympic Park.

The Botanic Garden would like to thank the The Finnis Scott Foundation and The Monument Trust for making this project a possibility.

Drop by and take a look, new plants are coming into flower on a daily basis.