In some areas of eastern England the month of September is often dry and the average weekly rainfall is less than transpiration. In these areas some watering will be necessary if plants are to receive all the moisture they need. Gardeners in all areas of eastern Britain and the East of Ireland should be prepared to water in September.

September is the first of the Autumn months, although after the occasional outstanding summer it can still provide spells of warm, dry weather. The effects of shortening days are much more noticeable. The warmth of the sun is decreasing, so that temperatures are rarely high; and the difference between north and south is much more pronounced than in August. The nights are appreciably cooler, and often very humid.

In good years high pressure can occur over the British Isles during September. Calm, warm summer days result and afternoon temperatures may occasionally reach 21C (70F) in south-east England, though they are much lower in northern Scotland. During dry still nights, with no blanketing cloud cover, dew and mist form readily, and early morning frost may once more be a hazard for the gardener. This occurs sporadically inland in valley bottoms and sheltered pockets, especially in northern areas, and may catch the gardener unawares, as surrounding hillsides and higher garden slopes usually remain well above freezing point.

During this month depressions usually bring periods of cool, wet, windy weather to the west, but drier, sunnier weather to the east, particularly to east Scotland. The weather is often unsettled in closing days of the month, and strong winds bring rain to all areas.

Occasionally north to north easterly winds bring much colder and drier weather, particularly in the second half of the month, and much over inland Britain. Gardeners should expect their first widespread ground frost of the season.

During September the gardener must take precautions against gales by ensuring that stakes and ties are secure, and be prepared to move plants indoors if frost is forecast.

Lawns

• Aerate, apply sharp sand or compost, and sacrify to remove debris.
• Reseed worn patches. Apply autumn fertiliser.
• Control weeds, fugal infections and moss.

Roses

• Remove faded blooms.
• Continue to spray against mildew and greenfly.
• For quality blooms on hybrid teas, remove small side buds from flower stems.
• Scatter wood ash or sulphate of potash on the rose beds and hoe it in.
• Tie the shoots of climbers into a fan shape.
• Prune climbers and ramblers which have only one flush of blooms, and also weeping standards,
• Take cuttings of mature side shoots and ramblers; and of this years growth from floribundas and hybrid teas.
• Continue to spray fortnightly against blackspot disease.

Hardy Herbaceous Plants

• Continue dead heading and cutting back.
• Finish preparing new beds, and hoe beds already prepared.

Dahlias

• Check ties as autumn gales can cause damage.
• Feed once a fortnight with a liquid fertiliser to produce good blooms and build up strong tubers.
• Save dahlia seeds and dry in a cool cupboard.

Chrysanthemums

• Select best outdoor varieties and label for propagating. Protect blooms with greaseproof bag, dusting the insides with DDT or BHC
• under glass Bring pot-grown varieties into the greenhouse by the middle of the month, preparing a level floor and cleaning the glass. Spray the plants with a combined insecticide and fungicide. Ventilate well, disbud late varieties and control aphids as necessary.

Gladioli

• Leave new corms undisturbed until fully matured.

Irises

• Cut off and burn leaves infected with leaf spot disease.
• Plant, Dutch, Spanish and English irises for flowering from May to July, choosing a sunny, well drained site.
• Plant l. reticulata in rows for cutting. Plant l. unguicularis in poor, well drained soil in sheltered position. Plant l. sibirica in moist soil along margins of ponds or streams.
• Spray or dust irises with DDT against caterpillars.
• Under glass Plant bulbous irises (Dutch, Spanish, English l.danfordiae) in pots, and stand in a cold frame.

Lilies

• Spray against aphids and botrytis.
• Start planting bulbs as soon as available.
• Lift small bulbs from around L.auratum and grow on in pots.
• Transplant well grown pots of seedlings. Sow seeds now or in springs.
• Propagate healthy scales broken off during transplanting.

Carnations and Pinks

• Prepare beds for border carnations and pinks. If not already done.
• Severed rooted layers from parent plants. Continue to harden-off rooted pink cuttings and plant out those that are now growing strongly.
• Stop newly planted pinks that start to run to flower.
• Put sifted bonfire ash in bags under cover to serve as a spring dressing, and store sifted dry soil to help with autumn planting.
• Under Glass Continue feeding perpetual flowering carnations. Remove shading from the glass this month. Damp down in hot spells. Disbud flower stems. Keep water from falling on opening blooms, and wire calyces of blooms which threaten to split. Cut blooms with long stems and stand them up to their necks in water in a cool place for 12 hours before arranging them in vases. Take action against pest and diseases.

Sweet Peas

• Purchase seed for sowing next month. Include some of the old fashioned varieties.

Flowers from seed.

• Remove fading annuals to make way for spring bedding.
• Sow the hardiest annuals to over-winter outdoors. Plant hardy biennials.

Bulbs

• Plant bulbs between shrubs or herbaceous plants on rock gardens or in lawns, preferably in groups.
• Remove summer bedding as it fades and replace with bulbs.
• First plan the layout then plant from the centre outwards. Where interplanting set the plants first and put in the bulbs afterwards.
• Indoors and under glass - repot arum lilies fro winter flowering. Prepare pots and bowls of bulbs to flower from Christmas to Easter, using bulb fibre. Ensure that indoor bulbs fill their pots or bowls with roots before they are forced, by planting them in dark, moist conditions for two to three months.

Alpines

• Transplant any plants which need re-siting. Start making a new rockery; but first consider whether a raised alpine bed might not be better. Choose an open well drained position away from trees. Allow several weeks to pass for soil and rocks to settle before planting.

Water plants and pools.

• Collect the winter bulbs of hydrocharis and utricularia before they sink to the bottom of the pool and keep them in an unsealed jar of water in cool place until spring.
• Pot up waterside primulas pricked out in June, or plant them in their permanent positions.
• Feed the fish, as live food is now becoming scarce and they must build up their reserves for the winter.

Greenhouse and Shrubs

• Start giving artificial heat towards the end of the month.
• Sow annuals for a spring display in the greenhouse, potting the seedlings separately in 3in pots. Take cuttings of fuchsias, zonal pelargoniums and many other greenhouse plants.
• Remove permanent shading from the glass. Bring primulas and other plants into the greenhouse from cold frames.

Trees and Shrubs

• Prepare ground for planting later in the month or in October.
• Start planting evergreen shrubs during showery weather at the end of the month
• Support standard shrubs with stakes until they become established. Water newly planted shrubs during dry weather and spray their foliage with water,
• Propagation under glass Take hardwood and half-ripe cuttings of berberis, juniper and privet, rooting them in sandy soil in a cold frame. Leave them to grow on in the frame during the winter. In open ground, cover with cloches during cold weather.
• Pruning. Lightly prune such shrubs as phlomis and senecio after flowering

Rhododendrons and Azaleas

• During rainy weather transplant bushes which need moving.
• Continue to increase stock by layering. Heel in plants arriving from nurseries if the ground is not ready for planting, but don't allow them to become dry.

Hedges

• Clip new growth for the last time in the season.
• Remove remaining weeds and burn or compost them.
• Prepare sites for new hedges. Plant evergreen hedges from mid September.

Heathers

• Prepare ground for planting, selecting an open position.

Fruit

• Plan for new planting season and order trees. Choose late flowering varieties for frosty areas.
• Grass down established .
• Remove trees infected with honey fungus.
• Prepare storgae places for apples and pears. and pick fruit in cool conditions before fully mature.
• Complete summer pruning of apples and pears
• Harvest blackberries and loganberries, cut away old growth, and tie in new.
• Prune well trained peaches and tie in new shoots.
• Spray cherries.
• Pick plums and damsons and prune trees.
• Pick September fruiting raspberries.
• Protect autumn-fruiting strawberries against birds and slugs, and cover with cloches in cold weather.

Vegetables

• In the south sow lettuces for overwintering with cloche protection.
• In the north plant spring cabbages. Lift main crop carrots and store sound ones in layers in deep boxes.
• Under glass Protect lettuces and spring cabbages with cloches. Sow carrots under cloches.
• Less common vegetables. Cut off the tops of chicory before blanching.

Herbs

• Sow parsley and chevril to provide a spring crop. Divide and replant clumps of bergamont.
• Under Glass Take cuttings of bay and rue. Take cuttings of lavendar and protect with a frame cloche.

Patios and Town Gardens

• Continue frequent watering and remove dead flowers. Discard plants past their best.
• Prepare containers for planting spring bulbs.
• Empty compost from containers not required during the winter.

House Plants

• Slightly reduce watering and feeding.
• Keep tender plants away from windows on cold nights.
• Transfer plants liking plenty of light from a west to a south window.
• Reduce the amount of water given to cacti.
• Complete repotting and pruning.
• Examine plants for overwatering or of pest attacks.
• Control red spider mites with derris or malathion. As these plants are encouraged by a dry atmosphere, try to increase atmospheric humidity around the plants.

General Tasks

• Clear away remains of crops that have finished.
• Order bulbs, roses, herbaceous plants. shrubs and fruit bushes.
• Take cuttings of evergreen shrubs, geraniums and hydrangeas.
• Check that electrical installations are in working order before the winter.
• Complete major construction jobs, particularly concreting.
• Check that gutters and drains are free of leaves and other debris.