Ask John Negus John will reply personally to all your gardening questions every week John has been answering reader queries for 50 years
How do I grow on my Dutchman’s pipe?
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I acquired some Aristolochia macrophylla (Dutchman’s pipe) seeds and got them to successfully germinate. However, I find I cannot get any real information about growing them and wonder if you could assist, please? Second, I have a serious allergy to wasp stings and have to carry two EpiPens with me. Are there any plants that deter wasps? Dorothy Reeder, Co Leitrim, Ireland I am delighted that you have raised some strikingly beautiful Aristolochia macrophylla from seed and have robust seedlings. Set them singly into 4in (10cm) pots of a compost mix formulated for seedlings, adding a quarter part, by volume, of coarse grit. Then grow them on in light shade in a temperature of around 66-70°F (19-21°C). When the roots fill the pot, move the plants into containers 6in (15cm) larger in diameter. This time, set your charges in a blend of Miracle-Gro ericaceous compost mixed with a quarter part, by volume, of coarse grit. Being a climber, your plant is best
Twig and leaf blight can be treated with a fungicide
Fungal issues
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Dutchman’s pipe germinate well in light shade and a warm temperature
trained over netting or trellis. A word of warning, though. If you have a cat or dog, please keep it away from the plant, because if the animal’s fur or hair comes into contact with the plant’s toxic leaves or flowers it may harm the animal. As for discouraging wasps from the garden, wormwood (artemisia) and mint are known to repel them, and there several fine and sculpturally pleasing species and varieties of each.
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What is wrong with my kerria stem? Chris Nower (via email) Your bush has succumbed to twig and leaf blight (Blumeriella kerriae). It is worse in wet weather when spores are dispersed by rain splashes, but Fungus Clear Ultra is usually effective against it. Initially, prune out the infected shoots and bin or burn them. Then, when new growth appears, spray repeatedly with the fungicide in spring and summer to prevent reinfection.
Pockets of acid soil can create a difference in hydrangea flower colour
Tobacco plants make a colourful splash in summer
Why is my hydrangea pink and blue?
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Do you know why my hydrangea is producing both pink and blue flowers? We live in the Chilterns and it’s quite thick clay soil, so I assumed we would have an alkaline pH soil and therefore pink flowers. I have not given the hydrangea any pH-altering feed. Victoria Love (via email) It is curious why some of your which is what you’d expect in the hydrangea flowers are blue and Chilterns. But the anomaly is the others pink. It’s almost certainly due to presence of blue flowers that change there being pockets of acidity within its to that colour when the pH is much root area. less – about 5.5-6 – and iron, Pink blooms are caused by a aluminium and other elements are relatively high pH, of around 7.5-8, readily available to trigger that change.
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Smoky beauty
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Can you tell me what this plant is, please, that’s in my garden? Sue Sullivan (via email) This is a variety of tobacco plant (nicotiana). A half-hardy annual, it is raised from seed in gentle heat in March or April and transplanted where you wish it to flower when frosts finish in late May or early June. There are several selections that have red-flowering forms, two of which are Evening Fragrance Mix and F1 Perfume Mix. Seeds are stocked by Suttons, Woodview Road, Paignton, Devon, TQ4 7NG ( 0844 326 2200, ✆ suttons.co.uk). 19 JUNE 2021 AMATEUR GARDENING 39
