Summer Sun cherry on Gisela 5 rootstock

Don Vaughan, a member of the FAST (Farm Advisory Service Team) based at Brogdale Farm, Faversham, recently talked to the RHS Fruit and Vegetable Committee on UK cherry production, which has been transformed by the use of new cultivation systems and new varieties. Don has been one of the principal movers behind these changes. We publish below an account of his talk. 

Magnificent stately cherry trees sheltering grazing sheep, the picture postcard image of the Kent countryside, have almost disappeared from the landscape. The total area of UK cherry orchards is down to 300 hectares from 700 hectares in the 1990s and 3,000 hectares in the 1950s, but the decline has been halted through the adoption of revolutionary new ways of growing cherries. The big old trees that needed 30-40 stay ladders to pick the crop have gone being impossible to net against birds, while  health and safety ruled out ladder work. In modern orchards the crop is picked from the ground, the trees are sufficiently small to be netted and hugely more productive than orchards of even a decade ago, due to the introduction of new dwarfing rootstocks and new varieties.  As a result, although the area of cherry orchards is only slowly increasing, the volume of fruit produced is rapidly rising because of much larger yields. 

The change of fortunes came about after Don Vaughan and a group of Kent cherry growers visited the USA in 1996 and saw orchards of cherry trees grown on the dwarfing Gisela 5 and 6 rootstocks. The trees were cropping heavily, although only four years old, and  'a dream to manage'. They immediately saw that this was the way the home industry could progress. English growers were using colt rootstock, but this proved to be one of the reasons why cherry growers struggled to get good, consistent crops. One year, they might achieve 10 tons/hectare with Stella, but in another year it could be only  2 tons/hectare, because of colt rootstock's sensitivity to winter chill and to weather and soil conditions after fertilisation. Gisela rootstocks, which were developed in Germany, offered and have delivered smaller trees, precocious cropping, no problems with winter chill, and tolerance of  a little frost because they set such a heavy crop. Gisela 5 has become the rootstock of choice for market growers and also makes a compact tree for gardens; Gisela 6 is slightly more vigorous. They do, however, demand high levels of husbandry and in a commercial orchard trees receive continuous monitoring: nutrition status in the tree is checked by taking leaf samples at regular intervals from fertilisation to harvest and feed applied as necessary through the irrigation systems. The amateur would have to bear in mind that trees on Gisela rootstock needing feeding to give of their best.

Most modern orchards are planted as two rows of trees with an alley in between. Training is minimal as most new varieties naturally have a spreading habit, which not only aids picking but lets plenty of air through the tree discouraging fungal infection and fruit rot. Training, when called for, involves tying the branches down or the more delicate operation of pegging the shoots so as to make a flat angle, for which Don advised chipolata sticks placed between the main stem and the branch. The two rows of trees are protected by covers stretched over a metal framework supporting netting to keep birds out and polythene to prevent hail damage and to reduce fruit cracking and also provide about two degrees of frost protection. The most sophisticated system is a combination of slatted polythene and bird netting, but costly at £14 -15,000/acre, on top of the £15,000 it takes to establish a cherry orchard. Even with all this protection, heavy rain at harvest time resulting in cracked fruit is still a hazard for the commercial grower, but a protein product called Pre-Tect is proving effective in reducing cracking and it seems likely to become available also to amateurs. There is one new threat, however, a pest that has appeared out of nowhere in the last couple of years - the light brown apple moth. It probably came in from Australia, its native habitat, and in two years has swept across Kent.  Young larvae can enter the fruit through the calyx or stem cavity with disastrous results. With three generations a year this is potentially a serious pest, although appears to be kept under control with current commercial sprays. 

While new rootstocks are revolutionising cherry orchards, new varieties planted over the last decade can take equal credit for the revival of the industry. Don provided a list of the main cherries now planted and which we are likely to find on sale; most also make good garden trees. A number have been raised in England at the John Innes Research Station when it was based in Hertfordshire in the post war years and more recently by Ken Tobutt at East Malling Research in Kent. Others have been introduced from Canada where the Summerland Research Station in British Columbia began producing self fertile cherries in the 1940s and 1950s. The first wave  included the well known Stella, Van and Lapins, but these are now being overtaken by a number of those listed below, as well as some from Europe. All  are black cherries, which survive the rigours of transport much better than white cherries, and according to Don are not 'all skin and stone' like the old varieties, but large and fleshy. (The Royal Horticultural Society Award of Garden Merit -RHS AGM - signifies that the variety is considered a good garden fruit). 

In order of ripening:
Vanda: the first to ripen and recently introduced; good eating; no tendency to crack even with heavy rain; not self fertile; pollinated by Summer Sun, Kordia. Raised in Europe and distributed by GEVO.
Merchant: almost as early as Vanda; likely to be the first available from farm shops; lovely flavour; canker resistant; not self fertile; does well on Gisela 5 rootstock. Raised John Innes Research Station.
Hertford: usually wins prizes for the best cherry; excellent flavour; firm; not inclined to split; not self fertile; consistent good crops on Gisela 5; awarded RHS AGM. Raised John Innes Research Station.
Cristalina: good looking cherry, but not depth of flavour of some others; not self fertile. Raised Summerland Research Station. 
Summer Sun: winner every year for its heavy consistent crops and first class flavour; nice flat habit, ideal garden tree; prone to canker; not self fertile, but always crops; awarded RHS AGM. Raised John Innes Research Station.
Kordia: taste panels across Europe rate this a top variety; lovely bold cherry; blossom  tends to be little frost sensitive; not self fertile. Originated in Czech Republic.
Sandra Rose: large fruit with the high sugar content demanded by super markets; tolerant to rain with little cracking; self fertile. Raised Summerland Research Station. 
Penny: excellent quality, very large meaty cherry; crops well and regularly on Gisela 5; not self fertile. Recently introduced; bred by Ken Tobutt, East Malling Research.
Skeena: destined to replace older variety Lapins; easy to grow with spreading habit; moderate tolerance to splitting; self fertile. Raised Summerland Research Station.
Regina:  large, good late cherry; crops well and consistently on Gisela 5; very resistant to cracking; not self fertile. Raised in Germany.
Sweetheart: latest of the season; very regular cropper; moderately tolerance to splitting; self fertile. Raised Summerland Research Station.
Staccato: will extend the season even later than Sweatheart, but not yet available in U.K; self fertile. Raised Summerland Research Station.

Report prepared by Joan Morgan