Clumber Gardener: September means it’s the height of the blackberry harvest

Chris Margrave, head gardener at Clumber Park
Chris Margrave, head gardener at Clumber Park
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September is the peak month for the blackberry harvest, although if the weather is mild, cropping can continue into October.

We grow around a dozen varieties in the soft fruit area of Clumber’s walled kitchen garden, along with several hybrid berries such as the Logan, Boysen and Tay berry, which are crosses between blackberries and raspberries.

Traditional blackberry varieties bear their fruits on stems which have grown in the first year, over-wintered and then produced flowering side shoots from these stems in their second year.

They are generally very vigorous and need training so that cropping stems can be separated from the developing stems to allow air and light into the plant and to make picking the fruits easier.

The decorative cut-leaved foliage varieties can even be trained over arches.

The foliage of Oregan Thornless, for example, takes on rich autumn colours.

For the past three years the Royal Horticultural Society has been trialling blackberries.

They are comparing varieties for plant habit and vigour, fruit yield and quality, length of season, susceptibility to pests, diseases and frost and for ease of picking, especially taking into account the amount of thorns on the stem.

They have already made recommendations from previous trials and given the Award of Garden Merit (AGM) to a number of reliable varieties.

Three varieties that have been awarded the AGM are Silvan, a vigorous, thorny and early ripening, producing its first fruits in July, Fantasia, which has very vigorous, thick, thorny stems and berries that are large and well flavoured, and Loch Ness which has thorn-less stems and gives high yields of top quality fruit.

The latest result of blackberry breeding is Reuben.

This is a primocane variety, producing fruit on the first year’s growth – on seven-month old canes – in the same way as an autumn fruiting raspberry.

It is pruned in the same way with all shoots cut down to ground level in late winter.

Developing stems can be trained onto poles, walls or trellis and by September they will have grown to about two metres high with a spread of 1.2 metres.

Flavour is described as very sweet, even sweeter than a sweet tasting strawberry, and the berries are large, sometimes reaching the size of a plum.

At Clumber, we grow our blackberries and hybrid berries on our west, east and northerly facing wall, which gets sunshine from about mid-afternoon.

Pests and diseases are generally not a problem.

Birds, especially blackbirds, may take the crop and if this is troublesome, fruiting plants can be covered with netting if fruits become a target.

Blackberries will tolerate partial shade, but yields will be higher in a sunny spot.

They should be planted into soil which has been dug, cleared of perennial weeds and had organic matter such as home-made compost or leaf mould added to it.

It is best to wait until November, when bare root plants will be on sale. These are usually cheaper than container-grown plants.

Now we are into September, continue watering, feeding and removing faded flowers from plants in containers and hanging baskets to keep displays looking attractive.

This is one of the peak harvest months in the fruit and vegetable garden, especially for tender crops such as French and runner beans, sweet corn and outdoor tomatoes.

Order, or buy, spring flowering bulbs.

Daffodils and narcissi benefit from September plantings, while tulips and hyacinths are best planted in October.

Lawns can be scarified with a springbok rake to remove moss and “thatch” (dead grass stems) and fed with an autumn fertiliser low in nitrogen.

Raise the height of cut of your mower to around three centimetres.

September sees summer drawing to a close and daylight hours getting noticeably shorter, so make the most of the season by visiting gardens with kitchen gardens and herbaceous borders which will be looking good.

Many gardens will be holding pear or apple events.

Clumber’s walled kitchen garden is hosting an apple afternoon this Saturday between 12noon and 4pm when visitors will be able to sample some of the early ripening apples.

Further details are online at www.nationaltrust.org.uk/clumber-park