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In your ornamental garden in September

September does not have to be the end of summer. Even though many plants will be past their best by now, some care and general maintenance will keep the gardening flourishing often into October. This is also the time to take a long hard look at your garden. Be brave and ruthless! If plants have not performed well, it’s time for them to go, and be replaced by something more rewarding.

Things to do in the ornamental garden this month

• Greenhouse and conservatory
  The warm days and cool nights of this month require careful management. Fungal spores love this time of year – it’s perfect germination time for them. Plants can be scorched by the sun – it’s still hot enough. But cool nights can lead to tender plants suffering.
• Keep doors and windows open during the day unless the weather turns really chilly.
• At night the door can be open part way, about two fingers wide, as long as no frost is forecast. And as long as there’s no cold wind from the north.
• Remove shading by the middle of the month.
• Water plants less frequently, and avoid at all costs wetting the foliage. Damp foliage = fungal spore germination. If there is dew on the plants first thing, shake the leaves gently to help them dry off quickly.
• Throw out any leaves that start to develop a grey fuzz, or become slimy and brown. Clean the glass, inside and out, to remove summer dust and muck.
• If you plan to bring plants from the greenhouse indoors for the winter, check them thoroughly for pests. Look for mottled leaves that would indicate spider mite. ##Look for rolled and webbed leaves that would indicate larvae lurking. It’s often a good idea to shake off the top centimetre of soil to clear out any pests near the surface. Replace with a layer of grit. Next spring shake off the grit, and replace with some clean potting compost.

• 
  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 under cover towards the end of this month, well before the first frosts. Check the plants over thoroughly for pests and diseases, particularly red spider mite. Before bringing into the greenhouse, remove all dead and dying foliage, and if plants have been in pots outside, it’s worth scraping off a thin top layer of soil and replacing with grit. This will often clear out pests nestling in the surface layer.
• Cannas can be lifted after flowering as can dahlias. 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 frostfree area.
• If you have open soil, sow some parsley seeds now to provide you with a crop all winter.

• Garden Organic members can view our factsheet on red spider mite.

Keep the garden performing well

• 
  Camellia in flower
• Water camellias, rhododendrons and azaleas during dry spells to safeguard next year’s flowers. This is particularly important if it has been a dry summer, and the plant is in the ‘rain shadow’ of a wall or fence. Dry soil at this time of year will lead to bud drop next spring.
• Remove dying and dead flower heads daily. This will clear away potential sources of disease as well as encourage plants to produce a new flush of flowers.
• Hanging baskets and containers filled with summer bedding will be looking tired by now. But if you continue to feed and water them, they should last at least another month. Rain bounces off foliage, so watering is vital, even if it’s raining. Plants’ roots will have filled most baskets now, and the compost will have definitely run out of food. A tomato feed with high levels of potash works wonders on baskets too.
• You can also revamp your containers this month. Clear out the tired bedding plants and replace with a selection of plants that will remain cheerful and attractive winter-long. Evergreen herbs, such as thyme or oregano, look good. Euonymous fortunei ‘Emerald Gaiety’ makes a great centrepiece. Its white and green leaves turn pink in cold weather. A variegated trailing ivy can be added too. If you underplant with bulbs, you can have a stunning display through winter and spring. Plant the bulbs first, leave spaces for the evergreens, then plant those on top. This also makes a good present for someone with a small garden.
• Organic Tomato Feed is available from The Organic Gardening Catalogue
• If your containers are not raised on bricks or pot ‘feet’, now’s the time to do this. Heavy rain can flood containers overwinter, and rot plants’ roots. Raising the container allows water to drain freely.
• Get ready for the autumn leaf fall. Leaves can be stored in purpose-built containers, or just piled up behind shrubs and trees in an out of the way corner. Leafmould is the best soil conditioner ever, so collecting fallen deciduous leaves in autumn, and digging them in once they’ve rotted down, will give your soil a boost.
• Rose leaves affected by blackspot should be removed and put in the green waste bin. Remember to pick up leaves that are on the ground too. All the spores need to be cleared away if you’re to reduce infection.
• Don’t cut back too hard in the autumn ‘clear up’. Hollow stems and tussocky plants make perfect overwintering sites for a huge number of beneficial creatures. Piles of leaves swept under a hedge will also benefit wildlife looking for shelter. Don’t be too tidy!

• 
  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 dislike cold, wet winters so take stem cuttings now to overwinter under cover, and make sure you have plants next season.

  • Take a strong, non-flowering shoot about 10cm long
  • Remove the lower leaves, trim to just below a leaf joint
  • Insert into a pot containing a peat free, multi purpose compost mixed with grit –1 part grit: 4 compost.
  • Cover with a plastic bag supported with a bent wire frame to prevent the cutting touching the sides and rotting.
  • Place the pot out of direct sunlight either in the greenhouse, or somewhere cool indoors.
  • Once rooting has taken place after 3-4 weeks, harden off gradually to acclimatise to reduced humidity and increased light
  • Keep in a frost-free greenhouse or a cool conservatory until spring.
Some recommended cultivars:
'Apple Blossom' - white throated, pink flowers,
'Burgundy' - wine red flowers and
'Alice Hindley' - violet blue flowers.
• 
  Bulbs A good source of
  food for bees early in
  the year
  Get your bulbs now. As well as planting in borders and containers, why not plant 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.
• Plant bulbs to fill in spring gaps. If you have planting that has sprawled everywhere, but you know will die back and leave just plain soil early in the year, carefully part the foliage and plant bulbs in between plants. This works really well round herbaceous perennials that die down overwinter. Bulbs will have flowered and be out of the way by the time new growth starts next year. When you plant the bulbs, mark the outline of
  
  Fritillary meleagris
  your planting group with small sticks or pieces of bamboo cane. This will indicate the presence of bulbs underground and thus avoid damage during general garden work in winter.
  Ecobulbs are available online from The Organic Gardening Catalogue.

• Seed saving
  
• Look for seed heads that are turning brown and papery. Cut them from the plant, pop into a paper bag and finish off drying indoors. Shake seeds into the bag then transfer to an airtight container. 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 a lot to compost in autumn, but it is important to avoid the lure of the bonfire. All this wonderful organic material will be transformed into nutrient-rich garden compost. It just takes a bit of time. Pile up excess material next to your compost bin, or store in bags until there is room in the bin. Or make a new bin! Runner beans are likely to overwhelm most compost containers. Once you’ve cut them down, try leaving them piled on the ground. They will protect the soil overwinter, and slowly breakdown in situ so that by next spring you’ll easily be able to fit them in the bin.

• See our factsheets:

  • How to make compost (no password required)
  • Building a compost box
  • Buying a compost box
  • Making leafmould
    
    If you find these factsheets helpful and would like to support the work of Garden Organic, you can find out more about Garden Organic and its work by clicking here

JUST OUT! The Garden Organic book of compost !NEW

Available from The Organic Gardening Catalogue and all good bookshops and garden centres. If they don’t stock it, please suggest they do!

Hedges and lawns 

Give hedges a final trim this month. If you leave the trimmings on the ground tucked under the hedge, they will provide excellent winter shelter for a whole range of wildlife. Now is the time that creatures such as hedgehogs and frogs are looking for hibernation sites. A thick pile of hedge trimmings is perfect.

Lawns don’t need feeding now, but they will benefit from some work. They can become very compacted during the summer.
Use a lawn rake to clear out any thatch. Then aerate the whole lawn. It’s easy to do if you hire a machine for the job. And if you have neighbours with lawns, you might be able to share the costs of a days’ hire. Trials have shown that spiking with a fork is not only REALLY hard work, but doesn’t get down deep enough. Use the machine built for purpose. The best ones take out a core of soil, leaving holes into which you can brush a soil conditioner. If you have plenty of leafmould, that is perfect. On large lawns, you can either choose to treat just part of the lawn where activity has been greatest.

If your lawn is mossy, then that is a symptom of an underlying problem. Compaction, cutting too short, poor drainage, heavy shade, all of these conditions will encourage the development of moss. Often, just aerating, brushing in a conditioner, and raising the cutting height is enough to get rid of moss. No need for chemical treatments at all.

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. This is sold as Nemasys Vine Weevil Killer. When emptying hanging baskets and other containers, keep an eye out for the plump white grubs, and destroy them. If you have fuchsias in containers or baskets you can be almost 100% certain to have vine weevil larvae present.

• Nemasys Vine Weevil Killer is available from The Organic Gardening Catalogue
  Garden Organic members can view our factsheet Vine weevil for more information

Before bringing plants in to the house or greenhouse give them a good check over for pests. Warm conditions under cover will allow pests to overwinter easily.

• Remove curled or webbed leaves where larvae can hide.
• Check root balls for vine weevil larvae. If necessary wash roots clean and repot with fresh potting compost.
• Inspect under leaves for red spider mite.
• Clear off all detritus from around the plant to remove hiding places.

Summer flowering geraniums (Pelargoniums) and bedding fuchsias can be cut down to one bud when you bring them in. Keep them frost-free, and in a well-lit, airy spot. They’ll slowly regenerate during the winter months. They need to be kept just moist during winter.

Easy perennials for September

Ice plant (Sedum spectabile) is a wonderful showy autumn perennial. Flowers are in a range of red and pink. Leaves are usually a grayish green, but some have a burgundy tinge. Butterflies adore this plant and will cluster in huge numbers to feed now and next month. The dried seed heads make excellent food for birds in winter.

Chrysanthemums come in all shades and heights, and make a fantastic display this month. They can be grown from seed, usually in spring. They make a stunning splash of colour in the garden, and look wonderful alongside asters.

Grasses are at their peak now. Miscanthus especially is in its prime. ‘Silberfeder’ is particularly dramatic with reddish/brown flower heads up to 8ft high. In winter the plant turns a silvery brown and still retains interest. Its tussocky base is a good overwintering site for wildlife.

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 ideal for attracting beneficial insects into the garden late in the year.

Check out the September 2010 website archive on Ornamentals.  You’ll find extensive details about aster varieties.

Ponds

Early September is the perfect time for tidying up garden ponds. Hibernation has not yet started, so you won’t disturb creatures that have settled in for the winter. Ponds need to be managed, and a clear out every 6 years or so is often beneficial.

• Pull out any blanket weed.
• Remove all duckweed – if you can. The trick with duckweed, and blanket weed, is to keep on top of it throughout the season.
• Lift plants that have become too big and reduce in size.
• Remove dead foliage around plants.
• Reduce the quantity of floating plants if there is overcrowding.

Leave all plant remains in a pile by the side of the pond for the time being. This allows creatures caught up in the strands to crawl back to the water.
Now scoop out the ‘gloop’ that will have collected at the bottom of the pond. This will be rather revolting black sludge, a mixture of rotted leaves and pond waste, as well as anything that’s blown in. Get out as much as you can, but leave some behind as it will be filled with water creatures.. You may find some frogs! Just pop them into a bowl/bucket of water with a bit of pond plant and a brick so they can shelter or climb up. 

• Now re-plant with your smartened up plants and return the frogs to their home.

• Compost all plant debris, including the ‘gloop’.

Need inspiration?

Why not visit a garden near you? See what they are growing at this time of year. Check out their best autumn plants and get ideas for your garden.

 

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