15 Mar
2015
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Busy Lizzie Downy Mildew

Impatiens downy mildew is a fungal disease that causes yellowing leaves, leaf loss, and death of bedding Impatiens, commonly called busy Lizzies, during wet weather and damp conditions. Attacks are most likely in summer or spring in greenhouses.
Impatiens downy mildew quick facts

Common name – Impatiens downy mildew
Scientific name – Plasmopara obducens
Plants affected – Impatiens walleriana (busy Lizzies)
Main symptoms – Yellow leaves, leaf and flower loss, white fungal growth
Timing – Summer, or spring in greenhouses

What is impatiens downy mildew?

Impatiens downy mildew is a disease caused by the fungus-like organism Plasmopara obducens.

It was found for the first time in the UK in 2003 and is likely to have arrived on imported commercial propagation material (seed or cuttings). Statutory action was at first undertaken by FERA against confirmed outbreaks of the disease, but this soon ceased. After the wet summer of 2008, damage was much reduced by improved control practices at commercial nurseries. However in 2011 control failed, probably due to resistance to the commercial fungicides used. Infected plants were inadvertently sold widely. This led to the the most widespread outbreak of the disease so far, with many gardens, nurseries and local authority displays affected.

Outbreaks of downy mildew have been confined to Impatiens walleriana, the common bedding busy Lizzie. No cases have been found on New Guinea impatiens, Impatiens × hawkeri, or on the few species of Impatiens found growing in the wild in the UK including Himalayan balsam (Impatiens glandulifera).

Symptoms
You may see the following symptoms:

On leaves: Affected leaves turn yellow and are rapidly shed from the plant. A fine white fungal growth may be visible on the lower leaf surface, but affected leaves decay rapidly
On flowers: Flowers are also commonly shed, and the plant is often reduced to bare branches with a small tuft of yellow leaves and flower buds at the tip. Severely affected plants will eventually die
There have been some reports of variations in disease severity between different varieties, but these have yet to be confirmed.

Control
Non-chemical control
Affected plants should be disposed of as soon as possible. Do not compost them. Ideally burn them or bury them deeper than 50cm (20in). Although the spores should not survive the commercial composting used for council green waste collections, it is best to deal with contaminated material within the garden.

Because of the risk of soil contamination, rest affected areas from Impatiens for at least a year (some species of Plasmopara affecting other plants produce resting spores that can survive for several years).

Where infected plants have been grown in containers, replace the compost and wash using a garden disinfectant, as directed by the manufacturer, to cleanse the container if you intend to grow Impatiens in it again the following year. The disease is specific to Impatiens, so any other bedding plants can be grown without risk. Semperflorens-Cultorum begonias and bedding fuchsias perform well in the shaded areas for which busy Lizzies are invaluable.

Raising plants from seed will eliminate the risk of purchasing infected plants. This type of disease often has a lengthy ‘latent period’, when plants are already infected but not yet showing obvious symptoms. The advent of fungicide-tolerant strains of this disease increases the risk of introducing disease when buying plants.

Unfortunately, growing Impatiens, even ones that have rasied at home, in another part of the garden will not guarantee freedom from infection, as the disease may well arrive again as airborne spores from infected plants growing elsewhere. No resistant cultivars are yet available.

Chemical control
There are no fungicides available to gardeners for the control of this disease.

Biology
Downy mildews are a large group of plant diseases caused by microscopic fungus-like organisms related to the pathogen that causes tomato and potato blight. Despite a similar name and certain similarities in symptoms, they are unrelated to the powdery mildews.

The disease is spread by spores produced on the underside of infected leaves. These spores are splashed by rain, and are also carried for long distances on the wind. Extended periods of leaf wetness are required for spore production and infection, so severe outbreaks of downy mildew are only likely to occur during wet summers.

The airborne spores remain viable for just a short time, but it is thought that the fungus can also produce a second spore type (a resting spore) within the affected plant tissues. These resting spores are much more resilient, and are released into the soil as the diseased material rots down. They are likely to survive within the soil for an extended period.

15 Mar
2015
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Bedding Plants – Latest Trends

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Many gardeners colour their summer garden with seasonal bedding plants. Most will plant a few pots, maybe a hanging basket, or fill in the gaps in beds and borders with flowering and foliage plants designed to deliver a display in the summer months. Even if you haven’t got a garden you can enjoy a window box or a pot on the doorstep brimming with summer colour. Those of us that have been gardening for a few years will remember simple annuals like alyssum, clarkia and godetias that we bought as a packet of seeds that we sowed directly where they were to flower. Other bedding plants were sold in late spring and early summer, often lifted directly from the seed tray and wrapped in paper to take them home. The selection was limited: red salvias, blue lobelia, mixed antirrhinums and maybe a few pink petunias. How the bedding world has changed!

Bedding today is big business globally. Bedding plants deliver flowers and quick colour: just what gardeners crave. They are also widely used in commercial schemes, parks and gardens and to bring colour and life to urban spaces. The demand has driven the quest for new varieties, weather and pest resistant varieties and a much wider palette of colour and texture. Most growers buy from plug suppliers: these are the producers of tiny young plants that are despatched early in the season to grower nurseries who produce for retailers and commercial contractors.

On the hottest day of the year in 2014 I visited the trial grounds of Ball UK, one of the biggest names in the bedding business. They hold a summer showcase over several weeks where growers come to choose the varieties they will grow the following year; some growing to sell, some for schemes in gardens, towns and commercial projects. Journalists and photographers also visit en masse to find out what’s new and see the trends for the coming year. This is a really important aspect of the summer showcase for Ball; the media introduce the plants to the gardeners.
imageThe trial grounds are just a mass of colour. Wandering through them is a great way to compare the performance of varieties, especially after a few days of searing heat which they’ve experienced this summer. In the display areas containers abound showing pot and basket plants in different contexts. So what took my eye?
Firstly lots of herbaceous perennials have found their way into the world of bedding: digitalis, althaea, echinacea, diascia, and a host of others. I was particularly taken by some fine agastache, that prairie perennial I mentioned last week. Its spikes of deep blue flowers were a magnet for bees and butterflies. I’m on the lookout for those anyway in preparation for my Gardening for wildlife course which is launched later this year.
Throughout the trial grounds you notice how single flowered plants are so attractive to pollinators. Two blocks of zinnias illustrated this beautifully: the double ones were left along while the single flowered ones were swarming with bees. I suppose I hadn’t really considered how important this group of plants is to bees and butterflies. We should all plant more of them: great for colour and great for wildlife.
In the covered display area plants for pots and baskets are the focus. I think lobelia has come a long way. New varieties last longer and keep blooming; the old varieties always seemed to be spectacular early in the year, but they ran out of steam by mid summer. A display of Lobelia Waterfall varieties was just soft globes of delicate flowers in shades of blue and lilac. Who couldn’t love them?
In contrast the Portulaca Tropical varieties just shout warm sunshine. Displayed in tall terracotta planters their silky blooms in wild tropical shades would transform any sunny patio into a sundrenched terrace. I soon found myself yearning for a rum punch.
Pelargoniums in all their various forms and colours are as popular as ever. Pots of double zonal pelargoniums (geraniums) display an amazing colour range. Personally I always think they look better from a distance than they do close-up. Their flowerheads are so long lasting there are always dead blooms tucked away in the centre of each flowerhead which makes them less appealing on close inspection.
I do love the jewel like Angel Eyes Pelargoniums. These are really mini-forms of the lovely Regal pelargoinums that are always better on a sunny windowsill than they are outdoors. Given a sunny position and a dry summer Angel Eyes are far freer flowering and sit more happily with other container subjects such as verbena.
Talking of miniature forms these are a strong trend in the world of petunias. The past couple of years have seen numerous black petunia varieties and these are now teamed up with lime green ones. I think this is a stunning combination but once you’ve done it maybe it’s time to move on. A bit like slate grey hellebores I love the idea of them and like them close up but they don’t seem to contribute much in the garden. The new Petunia Littletunia varieties ( horrid name!) I really like and they look as if they will be very floriferous and more weather resistant.
There is a strong trend towards designer mixtures using more than one variety. I know these are already very popular in the US and they are a growing trend here. These use two or three varieties of different plants with similar habit and similar flower shape: callibrachoa, diascia and bacopa are a good example. The overall effect is light and pretty. Look out or more of these in the next few years.

 

 

19 Feb
2015
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Hanging baskets

Whether planted for summer or winter interest, hanging baskets provide valuable colour at eye level. Choose vibrant bedding plants for a short-term show or herbs, shrubs and evergreens for a long-lasting display.

WHEN TO PLANT A HANGING BASKET

Plant summer hanging baskets from April onwards, but they will need protection from frost until the middle or end of May. If you do not have a greenhouse, it is usually easier to plant in situ once the frosts have passed.

Plant winter hanging baskets between September and October, and it doesn’t matter if they are frosted as the plants are should be hardy.

You would normally plant up a long-lasting perennial hanging basket from April onwards, depending on the types of plants being used.

HOW TO PLANT A HANGING BASKET

The basic principals of creating a hanging basket for winter and summer are the same.

Lining
First of all, if you are using a standard wire basket, it will need to be lined. You can buy readymade cardboard liners and fibrous materials sold for the purpose, but a thrifty option is to collect moss from the lawn. Aim to cover the inside with about a 1.5cm (½in) thick layer of the material and then half fill the basket with compost.

Compost
A multipurpose is fine for a display that only has to last for one year, but John Innes No 2 is better for a longer-lasting arrangement. And if you want to grow plants such as winter flowering heathers, it is best to go for ericaeous compost, although Erica carnea and E. × darleyensis cultivars are tolerant of other composts that contain lime.

Also consider using water-retaining granules to help reduce the chore of watering.

Choosing and arranging the plants
When you begin to arrange the plants in the basket, it is usually easiest to start with one, central plant. This can be used to create structure and impact, which is particularly important in winter if its other companions fail to flower in cold snaps
Around this, position some trailing plants to cover the sides of the basket, particularly if it is made from wire. However, using a more decorative basket is best where it will be easily seen
Along with this selection, it is worth considering carefully the flowering plants. Choose colours that work well together and plants that flower reliably. For example, winter-flowering pansies, petunias, lobelia and geraniums are always winners
Finishing touches
Once all the plants are in, fill around the rootballs carefully with more compost, firming gently. You can push in some controlled-release fertiliser pellets or plugs at this stage, and then water well.

AFTERCARE

Once the basket is planted, what else is needed?

Check baskets every day in summer, watering always unless the compost is wet. Drying out is an increasing risk as the plants grow and days remain warm
Although baskets don’t dry out as quickly in winter, they still need regular checking. Aim to keep the compost moist but not soggy, and avoid wetting the foliage and flowers
In spring, summer and early autumn (April to September), apply a liquid fertiliser
Deadhead regularly to prevent the plants’ energy going into seed production, rather than more flowers

PROBLEMS

Hanging baskets rely most on the gardener to ensure they don’t dry out. However, poor flowering can be remedied by trying the following:

Ensure the baskets stays moist but not soggy
Feed once a week with a liquid fertiliser
Winter hanging baskets do greatly benefit from a sheltered, sunny spot. If the position is exposed, consider giving the basket some protection in the coldest weather. Use either a layer of fleece, or sit the basket on a bucket in a cool greenhouse for just the worst days

Watch out for common pests such as aphids, slugs, snails and vine weevil. Diseases that may be troublesome include powdery mildew, pelargonium rust, fuchsia rust and impatiens downy mildew.

Some of the local businesses we supply hanging baskets to


18 Feb
2015
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WHAT IS WINTER-KILL?

When clear skies at night lead to a hard frost, growing media in pots can be frozen solid. Next day, plants in bright sunshine may need water, but can’t use it if it’s frozen. Those plants can become dry enough to deteriorate or even die. This post is about keeping them safe.

LOOK FOR DANGER

Check the bottoms of a few pots, to see whether they contain solid ice. Whenever you can see this, the growing medium above the ice is usually sufficiently water-logged for it also to contain ice, which will be very slow to thaw, even on a bright sunny morning. This can prevent plants from translocating enough free water to their upper parts, which become desiccated. Even a light breeze will accelerate this, leading to permanent wilting and “freeze drying,” just like instant coffee. I have known this do over £8,000 of damage in a small nursery in one morning.

PROTECTION

You need to prevent excessive transpiration until the root ball has thawed sufficiently. Fit your watering lance with a rose that delivers as fine a spray as possible. Open the supply valves fully, then turn the rose upwards, and use it to damp the foliage and stems lightly. In UK conditions you should try not to water the growing medium; the sun will thaw it faster if it is not water-logged. I suggest that in principle you should damp your plants over as soon as the problem is identified, and again last thing in the day, and again first thing in the morning. (Fruit growers use similar techniques to coat fruit buds with ice, because that prevents desiccation)

21 Feb
2013
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Winter/spring flowering bedding plants

When summer bedding plants come to an end, the garden can start to lose its colour and need brightening up. So autumn is the perfect time to plant autumn, winter and spring bedding plants into their flowering positions to take over when the summer colour fades.

 

These plants can provide several months of great garden colour and shouldn’t be missed.

There may not be as much choice as summer bedding plants, but anything and everything will be very welcome to provide colour for the garden over the colder and darker days.

 

The following are all available from our nursery between September and November and will flower for weeks on end through spring:

 

  • Ajuga Burgundy Glow
  • Ajuga Braun Hertz
  • Ajuga Golden Beauty
  • Lamium Beacon Silver
  • Lamium WhiteNancy
  • Lamium PinkPearl
  • Helichrysum Angustifolium
  • Artemesia Oriental Limelight
  • Veronica Prostrata
  • Cheiranthus Treasure Mixed
  • Cyclamen – Mini Miracle Mixed
  • Aubrieta

 

 

The mainstay of displays from autumn right through to spring are the winter-flowering pansies and violas. Primulas, primroses and polyanthus, although spring flowering, will also flower intermittently during mild spells in winter. You can also try dwarf indoor cyclamen (Cyclamen persicum); although not regarded as being hardy, they will usually last until at least the New Year in a sheltered location, even longer in mild areas.

Planting

Since plants grow very little in winter, make sure you start with good-sized plants, plant closely (most can be planted 15-23cm/6-9in apart) and use sufficient numbers to ensure a colourful display.

And because of the lack of growth in winter, the earlier you can plant out in autumn the better, so plants establish quickly and produce plenty of flower buds. This is particularly true for winter-flowering pansies.

 

Find out more about planting out

 

And for extra flower power, underplant with a wide range of spring-flowering bulbs, such as daffodil, crocus, tulip, hyacinth and allium.

 

Find out more about planting bulbs

 

Containers, pots & hanging baskets

And, of course, it makes sense to replant all your pots and hanging baskets, using fresh compost.

Find out more about the basics of planting up containers

 

Positioning planted containers close to the house will help ensure a bright and cheerful outlook, even if it’s too miserable to actually venture outside. The house will also help provide some winter protection for the plants and the containers.

Other low-growing plants that can be used for extra colour in containers include:

 

  • Winter-flowering heathers
  • Vinca minor
  • Ajuga (bugle)
  • Heuchera
  • Lamium (ornamental deadnettle)
  • Ivy

 

And, you can include some dwarf/slow-growing shrubs such as Skimmia, Euonymus fortunei and Sarcococca (winter box, with highly scented winter flowers). As with beds and borders, underplant with dwarf spring-flowering bulbs, such as daffodil, crocus and tulip.

 

Container care

For best results, position containers where they will get as much light as possible during the winter months. Water containers carefully in winter taking care not to overwater, so make sure you check the compost regularly as it can soon dry out during mild weather. Smaller plants are more susceptible to both over- and underwatering. It is not necessary to feed container plants during the winter, as fresh potting compost will have all the necessary nutrients. But start feeding with a liquid feed when growth starts in spring.

Raise pots and other containers off the ground on pot feet or bricks to help drainage and help prevent the conditions that can cause terracotta pots to crack.

Use bubble wrap around containers in very severe weather to reduce freezing damage to plant roots. Or make ‘duvets’ from thick bin liners filled with insulation material, such as shredded paper, polystyrene chips or even loft insulation material.

22 Feb
2012
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Domestic gardens revalued

One of the most significant trends emerging slowly but surely from the ashes of the housing collapse has been the shift away from the development of high-density flats and towards homes with gardens.

Horticulture Week reported in detail on the trend last year following the release of exclusive research on the progress of the UK’s key regeneration projects – and will be reporting on the updated findings in June.

This return to developing homes with gardens, while largely driven by the spectacular drop in flat values in 2009, has also been fuelled by the ending of housing-density targets – long blamed by many landscape designers for squeezing out soft landscaping from residential schemes.

The latest twist in this trend towards a greater focus on gardens was aired at last week’s Landscape Show, where Barratt Homes eastern counties technical director Alison Crofton described how the housing crash has led to a complete overhaul of the house builder’s approach to landscaping. Where once soft landscaping was considered in the last few days of a 10-week process – and installed to specification in just 50-75 per cent of schemes – now it features at feasibility stage, staff are plant trained and green space from gardens to surrounding landscaping has climbed the agenda.

Says Crofton: “If a scheme looks good it creates hype, more people come to see it and it sells.” With the volume of UK house sales at a 40-year low and a slow recovery in prices predicted for post 2015, this welcome trend looks like it is here to stay.