The weather in September can vary from very warm sunshine to chilly wet days reminding us that autumn is just around the corner. Make the most of the the dry and sunny days as there is plenty to do in September to prepare for next year.  It is also harvesting time for many fruits and vegetables.

Flowers 

Dahlias are at their peak in September and if the weather is mild they’ll carry on blooming for several more weeks. Likewise cosmos, zinnias and Japanese anemones.

However, by late summer many gardens plants are starting to run out of steam. There is still plenty life left in them if you carry out few simple tasks:

• Feed and water plants during sunny spells
• Nip off spent flowers to keep the bloom coming
• Remove brown and ragged leaves
• Address powdery mildew  – a fungal disease  – keep watering and remove debris and overhanging growth to improve air circulation. 
• Stake top heavy dahlias and sunflowers especially when high wind is forecast.

Plant spring-flowering bulbs: September and October are the best times to plant daffodil, crocus and iris bulbs, tulips can wait until November. 

Saw hardy annual: Nigella, Honesty, Flax, Cornflowers, Poppies, Larkspur … Growing hardy annual flowers from seeds is quick and easy. They are able to survive frost, so can be sown outdoors in autumn. They will survive the winter to bring summer colour to your garden or even your plot. Many will attract pollinators.

• Make sure the area to be sown is weed-free.
• Dig over the soil to a spade’s depth, rake it over and firm.
• Plan the area to be sown by sprinkling grit or sand on the soil or score the ground with a cane to mark out sowing areas. Decide what should go where according to height, habit and colour.
• It is important not to sow into a soil that is too rich, since this may encourage leafy growth at the expense of flowers, so avoid using fertiliser.
• Scatter seeds thinly (or sow into drills) and cover lightly with soil or compost.
• Water well with a watering can fitted with a fine rose.

Plant out biennial: foxgloves, hollyhocks, sweet williams, wallflowers, forget-me not … If you have sown some back in midsummer, or you have young plants from self-seeding,  now is the time to plant them into their final positions.

Leave perennials for wildlife:  when tidying up your borders, resist the urge to cut back dying perennials. Many have seedbeds (sedum and thistles) for birds  and they can provide shelter for insect as well as protecting the soil from winter weather. 

Take cuttings:  It is your last chance to take semi-ripe cuttings of verbena, penstemon, salvia, lavender to increase stocks and beat winter losses.

1. Select shoots and trim to around 5 cm just below a leaf joint.
2. Remove the lower foliage.
3. Insert around the edge of a pot of compost.
4. Keep moist and out of direct sunlight to root.

Fruit and vegetables

Harvest apples: and lay them carefully to avoid bruising into an open shallow trays. Keep them in a cool frost-free and airy environment.

Harvest and store potatoes: dig them up now and keep them for your home-grown roast potatoes on Christmas Day. 

1. Once the stems have withered, lift potatoes carefully with a fork on a dry sunny day.
2. Leave then on the soil surface to dry their skins for few hours.
3. Brush any excess earth (don’t wash them) and pack into paper or hessian bags.
4. Keep your bags in a cool frost-free, dark, dry place. 

Courgettes and aubergines: pick them regularly to encourage the remaining fruits to develops.

Pumpkins: raise them onto a piece of slate or wood to prevent them from rotting.

Winter salads: Sow lam’s lettuce, mizuna, rockets, mustard leaves.

Plant a strawberry bed: September is the perfect time to create a new patch. 

Don’t forget 

• Tidy your pond: not to allow plant debris to build up. Tidy plants, thin out growth and put netting over the surface to prevent leaves from falling in to the water.

• Return houseplants inside preparing them for winter: tidy them up removing yellowing foliage, check for pests and ease back on watering and stop feeding.

• Neaten up borders:  trim back stems that have flowered in early summer. Cut back dead or flopping stems. 

• Protect soils: spread a thick layer of mulch over bare soil to reduce weathering from winter rains.

• Prepare for leaf fall: making a leaf enclosure to create dark, crumbly leaf mould also known as “black gold”.  More on how to make leaf mould and its benefits in the October Tips of the month. 

August is the month to sit back and enjoy your garden, while the weather allows. Enjoy your home grown vegetables fresh and preserve any surplus crop for the winter: freeze beans and make tomato sauce, jams, pickles and chutney. 

August is also the perfect time to plan for next year. 

Take notes and label your plants 

Make a note of plant successes and start thinking of your planting plan for next year. You might want to introduce a new colour scheme.  For this add details of the name, colour and height of your plants and keep a note of these on labels or on a note book or even a diagram.

Hardy herbaceous perennials  and summer-flowering bulbs

As they will lose their leaves and die down in autumn and winter, label any that you want to remember. Also make a note of any that have become overcrowded and will needs lifting and dividing in the autumn or to be moved to a better site.

Other jobs for August:

• Train and summer prune wisteria and rambling roses.
• Refresh and weed your strawberry patch.
• Prune raspberries.
• Tidy up hedges and shade up topiary.
• Encourage tomatoes to ripen by removing growing tip. 
• Water regularly in dry spells and make plenty fresh water available for wildlife. 
• Beat potato blight and limit it spreading by removing and destroying any affected foliage. Eat tubers from blighted crops as soon as possible.
• Harvest herbs and store them hanging them up to dry in a warm and well ventilated location. 

Midsummer weather in July should bring plenty sunshine with long warm days that continue late into the evening. Sadly this year, we haven’t had much warm days, but don’t despair, summer is not over yet! At least your water butts are full, ready for drier spells when regular and wise watering will be needed.

Flowers 

Weekly deadheading and feeding will help to maintain healthy growth and encourage more flowers. 

• Cut lavender for drying

A great way to keep shrubs neat and compact. Choosing flowers just as they mature, when they are the most fragrant. The best time is late morning – after the dew has dried but before the sun draws out the essential oil. Hang bunches upside down in a well-ventilated, warm dark spot.

• Care for sweet peas

1. Pick often
2. Water regularly: they are thirsty plants so check the soil at the base to see if they need water.
3. Feed regularly: every 10-14 days with tomato fertiliser, seaweed or homemade liquid comfrey. 

• Harvest cut flowers 

Early mornings or evenings are the best time when the stems are full of water and less likely to wilt.

• Collect and store seeds 

From ripe seed-heads from aquilegias, nigellas, poppies. Ensure that your seeds are dry before storing them in paper envelopes in a dark, cool and dry location.

Fruit and veg

• Water thirsty plants such as celery, beans, peas courgettes, pumpkins and tomatoes regularly during dry weather.
• Make the last pickings of rhubarb and and leave the stems in place; this will allow the plant to build up reserves for next year. Remove any flower spikes that start to form, cutting right down at the base. 
• Thin out heavy crops of apples, pears and plums and remove and remove any malformed, damaged or undersized fruits.
• Sow a last batch of beetroots, peas and dwarf beans  before mid-July for an autumn crop.
• Sow veg to harvest during the winter months. Kale, winter cabbage spinach, radicchio, carrots.
• Sow small batches of fast-maturing salad leaves and radishes every few weeks for continuous pickings.
• Cover brassica with fine netting to prevent cabbage white butterflies laying their eggs on the leaves.
• Continue pinching out any side shoots growing from the leaf joints of cordon tomatoes, also known as vine tomatoes. This will encourage the plants to put their energies into producing flowers and therefore fruits. 
• Peg down strawberry runners into pots of compost to root new plants.

Tackle summer pests and diseases 

Pests and diseases can thrive in warm weather. 

• Keep watch for pests such as lily beetles, snails, aphids and vine weevils and remove before they do too much harm.
• Look out for clematis wilt. Symptoms are wilting leaves and black discolouration on the leaves and the stem. Cut out all affected material and dispose of it in your household waste. 
• Stop rust damaging hollyhocks by pruning out affected leaves and dispose of them in your household waste.
• Watch out for blight. In warm damp weather check for dark edges on the leaves of potatoes and tomatoes. Cute out affected leaves and dispose of it in your household waste.

Don’t forget 

• Clear weeds regularly around your crops as they compete for nutrients and water.
• Continue slug hunting.
• Deadhead flowering plants (unless you want to keep and store seeds): to ensure the plant keeps producing more flowers rather than putting its energy into forming seeds.
• Cool down the greenhouse:  In hot weather,  temperatures inside can rise to extremes, causing plants to become stressed and to dry out. Make sure that vents are open on sunny days. Drape shade nettings over the outside of the greenhouse. Damp down in the morning, wetting hard surfaces inside the greenhouse (floor and shelves) to help plants cope with the heat.
• Prevent powdery mildew.  This fungal disease tends to affect plants in dry spells. Give plenty of moisture in summer and mulch after watering with a compost layer. 
• Prune wisteria. Cut whip stems back to five or six leaves after flowering for healthy growth and to control the overall size. Don’t cut the woody framework. 
• Continue to tie and train new growth on climbing plants.