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Correspondence Edition - Oxford Botanic Garden

Correspondence edition from the Oxford Botanic Garden.

Eric Robson is at the Oxford Botanic Garden for a correspondence edition of the show. Pippa Greenwood, James Wong and Matt Biggs answer questions from the GQT inbox, postbag and social media.

The panellists discuss Maple tree tapping, give suggestions for plants to grow next to Fuchsia magellanica and talk about propagating a Goat Willow. Thye also offer advice on how to ward off midges and recommend tomatoes to grow later in the season in a greenhouse.

Between answering questions, the panellists are shown around the historical Oxford Botanical Gardens by Deputy Director Dr Chris Thorogood.

Produced by Dan Cocker
Assistant Producer: Jemima Rathbone

A Somethin’ Else production for Ö÷²¥´óÐã Radio 4

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42 minutes

Last on

Sun 21 Apr 2019 14:00

Fact Sheet

Q1 – Can we move or prune a large Yew tree?

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Dr Chris – Show to a tree surgeon.

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Matt – Will take pruning, but I would keep an eye on it.

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Pippa – Employ a tree surgeon, or if you’re concerned about it being close to the house, structural surveyors can help. But before doing anything, check if there’s a TPO (Tree Preservation Order) on the tree, and what you’re allowed to do.

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Q2 – Old cherry tree with pink blossom, but at the root there are four new growths which produce white blossom – what is this, and what should we do?

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Pippa – This is a grafted plant and at this stage, it looks like the root stock has taken over. Must take anything off a prunus tree during the peak of summer months (mid-June – August), to avoid a fungal infection called ‘Silver leaf’.

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Matt – Ideally, those new growths should be cut away when you first see them; but at this stage, wait until late July/August, and cut these back at the base, and then all the energy will go into the cherry tree.

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Q3 – White grubs, identified as Drosophila suzukii, spread throughout all our soft fruits – what can we do?

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Pippa – First, check if all the fruit has been affected, but unfortunately, there’s not much you can do to stop this.

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Q4 – 10-year-old Magnolia stellata produces mid green leaves with some red around the periphery, but never the brilliant red as promised on the packet. What should I do?

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James – This red comes from anthocyanins which you find in berries and some trees, but Magnolia stellata does not have this in its genetics, so I would say this is wrongly labelled.

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Matt – Agreed.

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Q5 – I have a sweet Maple tree, which I’ve tried to tap for syrup to no avail – what am I doing wrong?

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Matt – Normally you would do it early in the spring, when the buds begin to grow.

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Dr Chris – I would suggest it might not be cold enough; Northern American states and Canada, this happens when it goes from -20 degrees into spring, and there’s a big change in pressure.

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James – You also need a lot of sap to produce not much syrup.

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Glass houses – built to grow Victoria amazonica

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Q6 – Canna bulbs that won’t grow.

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Pippa – Perhaps there’s a problem with the water, or the bulb might be faulty.

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James – Could be out of date; canna bulbs should look like ginger – plump, no wrinkling on the surface – if it looked at all dry or shrivelled, perhaps it was out of date. Otherwise, might not have been kept warm enough.

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Q7 – Last year planted ‘Mini Muncher’ cucumbers which have stopped producing fruit. I feed them using tap water with a pH 5.8 and have tried using ‘Epsom salts’. They are on a North facing wall.

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Dr Chris – Cucumbers are ‘monoecious’ – have both male and female flowers, so unless pollen is transferred, it’s not going to bear fruit.

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Matt – North facing wall might be too cold – South or South-West facing would be better and mist it to keep up humidity. Even better, keep them in a greenhouse.

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Pippa – In hot weather, cucumbers produce more male flowers; considering last year’s hot weather, this may have affected the growth.

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Q8 – Tomato suggestions to grow later in the season in a greenhouse (unheated but sunny and sheltered).

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James – Any type of tomato, but I wouldn’t grow from seed – grow from cuttings which will give you faster results.

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Matt – With reducing light and temperature change, could try the old trick of picking ready formed tomatoes and putting in paper bag with a ripe banana, and ethylene produced would ripen the tomatoes.

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Pippa – Remember to water much less than you do in the summer.

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Q9 – Tornado of midge flies coming into garden every evening at dusk. What can I do?

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Matt – Midge plant in Scotland, Myrica gale you can rub on your skin, or grow in the garden should keep the midges away. Or wearing something citrus or eating garlic might help.

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Dr Chris – Anything lemony: Melissa – Lemon balm, lemon-scented Thyme – things in the Lamiaceae family have volatile oils to act as a repellent. Also, rosemary and lavender if in a sunny spot.

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Pippa – Try to encourage swallows and swifts with starter nests.

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Q10 – I have a Fuchsia magellanica in my garden, but I’d like to grow something that will fit underneath, withstand the shade of the shrub when it is in flower, but can do something bright and colourful from around March until June.

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James – Painted fern.

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Matt – Bulbs; Narcissi, Muscari, primrose, tulips – Tulipa saxatilis, Chionodoxa – early spring bulbs.

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Dr Chris – Iris foetidissima, Euphorbia amygdaloides.

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Q11 – 6-year-old Photinias has lost nearly all its leaves. Potential black spot – is there anything I can do?

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Pippa – Photinia scab. Collect infected leaves to stop reinfection and improve air circulation in plant.

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Q12 – Periwinkle with different coloured petals – what is happening?

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Dr Chris – Genetic mutation, but it’s an unstable phenotype so hard to multiply.

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James – Could be a chimera; two genetically distinct individuals that are sharing the same anatomy, this often happens with animals. Alternatively, this could be a viral infection at the tip of the plant.

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Q13 – How do you take cuttings and propagate Goat Willow successfully?

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Matt – Take healthy growth, make a cut just below and above when the leaf meets the stem, find sheltered corner of the garden, fork in some grit and organic matter, put in ground leaving the cutting about 12 inches (30cm) out of the ground. Be patient – they should root. Otherwise, could try layering.

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Dr Chris – Could also try putting cuttings in water.

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