In your ornamental garden in September

September often seems like the end of the summer but with some planning and forethought your garden can be a riot of colour and attract many beneficial insects and creatures into your garden. Colour and form can come from lovely perennials like Asters, Rudbeckias and Helianthemum, along with a broad range of grasses to keep any garden looking fabulous well into next month.

Things to do in the ornamental garden this month

• Greenhouse and conservatory
  As autumn approaches and warm days are followed by cooler nights, remember to close the greenhouse doors well before sundown. Keep foliage and flowers as dry as possible by careful watering and remove dead flowers and leaves to prevent fungal infections such as botrytis.

• Remove shading but continue to keep the doors and windows open on warm days.

• Plant parsley in the corner of a soil bed for fresh leaves during the autumn and winter.

• Check greenhouse plants for pests and diseases, and treat any you find before bringing your plants in for the winter. Storing pests and diseases over winter is never a good idea.

• 
  Yam (left), Canna 'Durban' (right)
• Clean and tidy the glasshouse ready to bring in tender perennials at the end of the month. Cannas can be lifted after flowering as can Dahlais. Both can be potted and left dry till the spring or you can store the tubers clean and dry in the traditional Dahlia way in a frost free area.
  
• Gingers ( Hedychium ), Yams, (Colocasia, Alocasia) Bananas, (Musa, Ensette) Cannas and Palms should all be bought in towards the end of this month well before the first frosts. Check the plants over thoroughly for pest and disease, particularly red spider mite.
  Garden Organic members can view our factsheet on red spider mite.

Keep the garden performing well

• 
  Camellia in flower
• Water baskets and small containers daily, even during rain! Water bounces off a leaf canopy, and, even in a downpour, little rain will reach the potting compost.
• Water camellias, rhododendrons and azaleas that are in dry locations. A shortage of water at this time of year can cause flower buds to drop next spring before they open.

• Remove dying and dead flower heads daily. Not only will you remove a potential source of disease, but this simple act will encourage many plants to produce a new flush of flowers.Many summer shrubs and climbers will produce strong new flowering shoots if they are deadheaded.
  

• 
  Penstemons have been
  making a comeback

• Penstemons have been making something of a come back in popularity over the last few years. The flowers are bell -shaped and foxglove like in appearance and if you keep dead-heading, they flower all summer long in shades of red, white, pink and lilac.

  The foliage and form are attractive too with fresh green leaves reaching a height of 40 - 60cm.

  They prefer a sunny spot but will tolerate partial shade. They may not survive cold, wet winters so now is the ideal time to take stem cuttings to over winter as an insurance against losses.

  1. Take a strong, non-flowering shoot about 10cm long
  2. Remove the lower leaves, trim to just below a leaf joint
  3. Insert into a pot containing a peat free, multi purpose compost
  4. Cover with a plastic bag supported with a bent wire frame to prevent the cutting touching the sides and rotting.
  5. Place the pot out of direct sunlight
  6. Once rooting has taken place after 3-4 weeks, harden off gradually to acclimatise to reduced humidity and increased light
  Some recommended cultivars:
  'Apple Blossom' - white throated, pink flowers,
  'Burgundy' - wine red flowers and
  'Alice Hindley' - violet blue flowers.
• Plant bulbs for flowering next spring. Try planting Narcissus (daffodils) in lawns or under trees for a natural look. Plant them in drifts, rather than singly and choose smaller, less showy types. Select an area where you can afford to leave the grass long in the spring until the leaves have done their work to build up next year's bulb. Other native spring flowers such as snakeshead fritillary, Fritillaria meleagris and cowslips, Primula veris will give a natural look to your planting. Ensure that any bulbs that you purchase, especially native species are from a guaranteed source and not plundered from the wild.
• Seed saving
  Take advantage of nature's bounty, and save seed from some of your plants. Look for seed heads that are turning brown and papery. Cut them from the plant then let them finish drying indoors, before shaking out the seeds. Always store seed in an airtight container, in a cool dry place. A Tupperware tub in the fridge is the best place to store seed till next spring. Label each seed variety clearly. If you've bought seeds this year, and not used the whole packet, as long as you store them somewhere cool and dry or in the fridge, they will probably still be viable next spring.
• There is always lots to compost in autumn, so try to avoid the lure of the bonfire. If your compost bin is full, lift off the bin (or move the contents out) and cover the contents with a sheet of plastic or old carpet. This frees up the bin for a new heap. Alternatively, buy or make another one.
  See our factsheets:

  • How to make compost (no password required)
  • Building a compost box
  • Buying a compost box
    
    Note: To access the factsheets you will need the members' password. Find out Garden Organic membership here.

Pests & Diseases

• 
  Leaf damage by adult weevils
  
  
  Vine weevil adult
  
  
  Vine weevil larvae
• Powdery mildews are common when weather conditions are warm and dry during the day and cold at night, and on dry soils. They are often most severe at the end of the growing season.

  Powdery mildews are caused by various species of fungi. They can affect trees, shrubs, roses, perennials, annuals, bulbous plants, vegetables, fruits and many indoor plants. Each species of powdery mildew affects only specific types of plant. A few plants are susceptible to more than one type of powdery mildew.

  Garden organic members can view our Powdery mildew factsheet for more information.
• Vine weevil grubs can cause havoc in pots, tubs and baskets, eating roots and killing plants. The best control for this pest is Steinernema kraussei - a parasitic nematode that is watered on to pots at this time of year. When emptying hanging baskets and other containers, keep an eye out for the plump white vine weevil grubs, and destroy them. Nemasys Vine Weevil Killer is available from The Organic Gardening Catalogue
  Garden Organic members can view our factsheet Vine weevil for more information

Easy perennials for September

• Asters are good hardy perennials and very easy to grow. There are many to choose from and even some that will flower from now till mid December. They brighten up any garden as the evenings draw in and are essential for attracting beneficial insects into the garden late in the year. Growing plants that flower late in the year is a very important part of keeping the ecological balance of your garden in your favour.
• Asters have been called Michaelmas Daisies in Britain for many years. Some gardeners make a distinction by using the term only when referring to Aster novi-belgii. This name evolved through the latter half of the eighteenth century, before which, asters were referred to as 'starworts'. This name was first applied to a British native species, Aster tripolium, the sea starwort, and, later to the late sixteenth century introduction Aster amellus, Italian starwort. There are records of Aster amellus being cultivated in England as far back as 1596. Florists refer to Asters as 'September flowers' and are mainly used to describe small flowered Asters no matter what the time of year.
• There are many cultivars of the Italian Starwort properly called Aster amellus. They are all late flowering and come in lilacs, blues, pinks and purples and many combinations of these colours. Some are small flowers and some are larger flowered. There is a huge range of Aster amellus but only four that are widely available, many others are restricted to the specialist nurseries but are still very worth finding and growing.
  Use the RHS plantfinder to locate nurseries near you: www.rhs.org.uk
  

  1. 'King George' is a lovely purple blue with large flowers and flowering now. Flowers are well branched and lax, it should go on flowering for about a month. The plant forms strong clumps around 60cm tall, with large grey-green leaves and is excellent for hoverflies and bees. 'King George' was introduced in 1914 by A. Perry and the RHS have given it an Award of Garden Merit (AGM)

  2. 'Veilchenkonigin' (Violet Queen) introduced by K Foerster in 1956 (AGM) with small deep violet flowers held on short erect stems. The plant is generally small, with small narrow deep green leaves growing from a small clump. As you can gather this is a small aster but the colour is very worth having and it flowers this month and well into October.

  3. 'Brilliant' introduced in 1955 by T. Carlile is another lovely aster. Around 60cm tall with short branching sprays of bright purple-pink flowers held above a tight clump of clean green leaves and is quite frankly brilliant.

  4. 'Rudolph Goethe' introduced by G. Arends in 1914. This aster has broad branching sprays of lavender flowers and large pale green leaves. It is 75cm tall but nice and compact and tidy and generally never needs staking. This aster is particularly useful as it stands quite tall and flowers for around 6 weeks, well into October and some years even into November

• 
  Aster X frikartii
• Back in the heady days of Victorian plant breeding, the Reverend Wolley-Dod crossed Aster amellus and the newly introduced Himalayan import, Aster thomsonii to create Aster x frikartii. He exhibited the flowers of this very difficult cross in 1892 but strangely, it disappeared without a trace after this. It was not until 1918 that the Swiss nurseryman, Frikart managed to cross these two species again. He named them after the alpine peaks 'Eiger', 'Jungfrau' and 'Monch'. In 1924 he bred another cross and called it 'Wunder von Stafa'. 'Eiger' and 'Jungfrau' are like Aster amellus whilst 'Monch' and 'Wunder von Stafa' are both like stronger versions of Aster thomsonii. The only other cross between A. amellus and A. thomsonii was achieved by the famous and greatly respected nurseryman Alan Bloom in 1964 and he named his cultivar Aster x frikartii 'Flora's Delight'

Disease free too

• The cultivars of Aster x frikartii are said to be totally free from mildew and very frost hardy. They are also some of the longest flowering Asters available. There are reports of 'Flora's Delight' flowering from early summer till late autumn. All these cultivars are still available and well worth growing. 'Monch' and 'Wonder von Stafa' have been recognised with an Award of Garden Merit (AGM) from the RHS

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