Ask John Negus

John has been answering reader queries for 50 years John will reply personally to all your gardening questions every week How do I grow on my Dutchman’s pipe?

I acquired some Aristolochia

Qmacrophylla (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

Araised 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 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.

A l a m y Dutchman’s pipe germinate well in light shade and a warm temperature Twig and leaf blight can be treated with a fungicide

Fungal issues Q

What is wrong with my kerria stem? Chris Nower (via email)

Your bush has succumbed to twig

Aand 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

Why is my hydrangea pink and blue?

Do you know why my hydrangea is producing both pink and blue flowers?

QWe 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

Ahydrangea flowers are blue and others pink. It’s almost certainly due to there being pockets of acidity within its root area.

Pink blooms are caused by a relatively high pH, of around 7.5-8, which is what you’d expect in the Chilterns. But the anomaly is the presence of blue flowers that change to that colour when the pH is much less – about 5.5-6 – and iron, aluminium and other elements are readily available to trigger that change.

Tobacco plants make a colourful splash in summer

Smoky beauty

Can you tell me what this plant is,

Qplease, that’s in my garden? Sue Sullivan (via email)

This is a variety of tobacco plant

A(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).

Contact John Negus by email address below Email: amateurgardening@futurenet.com

If you collect and sow peony seeds (inset) they will slowly grow to make more plants

Can I use seeds to add to my peonies?

My peonies have finished flowering and have produced seedpods. Can I plant

Qthese to expand my peony bed? Alan Steele, Dalry, Ayrshire

I am delighted that your peonies

Ahave produced seeds. Wait until the seeds are ripe – when they are firm and relatively loose within the seed capsule – then gather them and sow them shallowly in pots of proprietary seed compost augmented with a quarter part, by volume, of coarse grit.

Plunge them to their rim in a coldframe or similar structure and be patient; they can take a year or more to germinate. But what an achievement!

Alternatively, sow them in wellprepared soil, adding grit, if necessary, to ensure good drainage, and cover seeds with jam jars firmly implanted in the soil.

In time, when your charges flower, you may find that they are similar to, or even better than, the parent’s blooms. When planting them out, remember that although they like moist soil, new plants don’t take kindly to being overwatered.

How can I regenerate my cactus?

My Christmas cactus is looking a bit sorry for

Qitself and has stopped flowering. A decade ago its blooms were magnificent. Can you tell me how I can revive it? Thomas Masterson (via email)

The best way to regenerate your

AChristmas cactus is to remove any obviously dead shoots and shorten it to within 6in (15cm) of the base.

Then repot it in loam-based ericaceous compost, augmenting it with a quarter part, by volume, of coarse grit. Water it in with clean rain water. Finally, position it in light shade to simulate its natural habitat.

Within three or four weeks, new shoots will proliferate from the woody stock to create a fine new plant.

Feed it with a high-potash tomato fertiliser when it is showing flower buds and water it regularly throughout the year.

Christmas cacti usually regenerate well with repotting and care

Quick questions & answers

Why did

Qour Clematis montana not flower this year? Sally Evans (via email)

These plants do occasionally

Ahave a ‘year off’ . Encourage it to bloom next year, which it almost certainly will, by feeding it with 2oz (56g) per sq/m of sulphate of potash. Apply it now, and in July and August, over the root area, and then water in.

Can I

Qsave wallflower seeds now for sowing? Aiden Taylor, MIlton Keynes, Bucks

Unless the seeds are

Acompletely mature – the seed cases will crackle and seeds rattle loosely inside them – they may have insufficient vitality to germinate.

Wait a little longer until the seeds are fully ripe before pulling up the plants and saving the seeds.

What is this flower and how do

QI care for it? Mr T Parkes (via email)

Your shrub is Deutzia x

Amagnifica. Prune after flowering by cutting back a third of older flowered shoots to lower side shoots or to a node (stem joint) and new stems will appear from stumps to flower next year.

John has been answering reader queries for 50 years John will reply personally to all your gardening questions every week

Oriental poppies don’t do well in very dry soil

Will my poppy ever flower again?

I have a beautiful white Oriental poppy that flowered for two seasons, but since

Qthen it has put up healthy leaves but never flowered. I have it in a pot, but would it be better in the ground? Diane Holland, St Helens, Merseyside

I am sorry that your Oriental variety

Ahasn’t flowered for a while.

The usual reason is that the root area is too dry. If this isn’t so and the potting compost is damp, encourage robust leaf growth and help blooms form by feeding with sulphate of potash.

Sprinkle it over the root area now and water it in, repeating the treatment monthly until September. Next year, start in April. Additionally, water freely when growth is active.

Ideally, in autumn, when leaves die back, move it to a warm, sunny part of the garden where it should bloom every year.

Potassium is a vital plant food that improves resistance to adverse weather conditions and improves performance.

Prune choisya after it has flowered

Pruning choisya

I need to cut back my choisya –

Qwhen is the best time to do it? Ginny Turner, Evesham, Glos

Choisya is an accommodating

Ashrub and is best tackled when the flowers have faded, in late spring or early summer.

Remove one third of the oldest shoots, shortening them to near ground level or to younger growth. Make sure you don’t spoil the shape of the plant, though.

After pruning, feed with blood, fish and bone or another organic fertiliser.

Can you name these orange

Qflowers? They were in the garden when we moved in and this is best year they have flowered. Paul Elliott (via email)

The

Aplant is day lily (hemerocallis). A native of China, Korea and Japan, it is well named, for blooms last for just one day before shrivelling and dying.

There are over 30,000 named varieties and yours could be ‘Jolyene Nichole’ . To propagate, divide the rootstock in autumn or early spring and plant divisions in fertile, freedraining soil in full sun.

What is wrong with my bay tree?

At the moment my bay tree is growing new

Qleaves, but it has also been attacked by a pest that curls and deforms its leaves and the edges end up dead and black. What is it and what would you recommend? Pilar Rose-Alcorta (via email)

Bad luck! Your bay tree is infested

Awith bay sucker, a minute pest resembling fluffy white stars that devours leaf undersides.

When feeding, this creature causes the Bay suckers cause distortion plant’s leaves to develop thick, distorted to the edge of bay laves bulges. Luckily, although this is unsightly, it doesn’t do irrevocable damage to the bay.

As for controlling it, if you are using leaves for cooking there are no insecticides against it, so pick off and bin or burn affected foliage.

If your tree is purely ornamental, tackle it with Bug Clear Ultra, a systemic pesticide that travels in the sap stream to all parts of the plant and guards against attack for three weeks.

Alternatively, encourage natural predators such as birds, ladybirds, wasp and ground beetles to frequent your garden.

Unknown beauty

Daylilies originally came from the Far East

lime, which bearded irises like, to raise your soil’s alkalinity.

Once your irises are flowering well, divide them every three years to stop the clumps becoming congested.

Contact John Negus by email address below Email: amateurgardening@futurenet.com

Why is my clematis starting to fade?

The flowers of my patio clematis

QNubia are fading. Do you know why this is happening? The pot is in the sun most of the day so do I have to water it each day? Second, can I cut my foxglove down to encourage new flowers or growth? Jan Schut (via email)

Clematis Nubia is a fetching

Avariety that normally flowers from May to September. It’s best to remove faded blooms the moment they occur.

If you water frequently to keep the root area damp, new flowering shoots will form to continue the display.

I suggest that you feed your clematis monthly with Vitax Q4. Start now and finish in September. Then, next year, begin in April.

Prune in March, shortening all stems to 8in/20cm, cutting to just above a pair of buds.

Most foxgloves are biennial, forming a rosette in their first year, and then flowering, seeding and dying in their second season.

I suspect that your plant is Digitalis purpurea, which is a biennial. If you wish to perpetuate it, allow the seeds to ripen,

Deadhead Clematis Nubia when flowers start to fade

then sow them immediately in a wellprepared patch of fertile soil in full sun.

When the seedlings appear, move them to a nursery bed to grow on for transplanting in October where you wish them to flower the following late spring.

How can I get my irises to flower well?

How can I get my irises to flower?

QI have several plants and they grow but never bloom. Christine Mepham (via email)

I am sorry that your irises – and

AI am assuming they are a bearded variety – are not flowering. The usual reason is lack of adequate sunlight. If they are growing in even light shade they will be reluctant to perform.

They also like a damp spot, or at least soil that doesn’t completely dry out. Also, when you plant, make sure the rhizome (root) is slightly above the soil and gets the sun for most of the day.

If you do not have an open sunny spot for them, encourage them to flower by feeding them with sulphate of potash. Sprinkle 1oz (28g) per sq m over the root area and water it in. Apply it monthly until September. Next year, start in April.

Additionally, if your garden is acid, work in 4oz (112g) per sq m of garden

A l a m y Bearded irises like full sun and soil that retains moisture Woolly aphids are common and can distort tree shoots

Woolly worries

What is this ‘cotton wool’

Qdeveloping on my apple tree? Sheila Blackmore, Surrey

This is woolly aphid, a pest that

Afeeds on sap and debilitates growth. Control it by spraying with BugClear Ultra for Flowers, Fruit and Veg and when the tree is dormant in midwinter, spray it with Vitax Winter Tree Wash to kill overwintering aphid eggs.

A woolly aphid colony will distort shoots, causing them to become lumpy. If stems are badly affected, cut them back to healthy tissue in late autumn to encourage robust regrowth.

Marrows won’t form without good pollination

Dying marrows

Why haven’t our marrows formed

Qproperly? They just turn yellow and fade away. Sheila Blackmore (via email)

This is because flowers were not

Apollinated. Remove the dead fruits and encourage more blooms by watering freely and liquid-feeding weekly with tomato fertiliser.

When lots of flowers bloom, remove a male bloom when fully open, strip off petals and dab pollen onto the stigma of a female bloom, characterised by a minimarrow beneath it. Hand-pollinated flowers will develop into fruits.