Dwarf Sweet Cherries - Managing Crop Load

Growing sweet cherries is always a challenge because of our weather issues in the north east - winter injury, spring frosts, hail and extreme wet weather that splits the fruit and dry weather that leaves fruit size too small to market against the large cherries from the west coast.

Dwarf rootstocks, primarily Gisela 5 and Gisela 6, have been used extensively for several years with the hope that they could provide smaller trees and bountiful crops with large cherries. Well, 2 out of 3 ain't bad. But, when it comes to marketing sweet cherries, the consumer demands large fruit and large fruit pays!

Here are a few tips that hopefully can help growers to achieve strong trees and larger fruit:

• Any really productive variety, self-fruitful or not, probably has no business on Gisela unless the grower is exceptional
  
• Absolutely, keep trees on Gisela as vigorous as possible - good consistent irrigation, good soil fertility, some foliar feeds also would help. Small trees have small root systems, so irrigation must be frequent, and nitrogen uptake is reduced if soils are allowed to periodically become dry.
  
• Thin the just-set crop as soon as possible, don't wait until June drop
  
• Remove weak and pendant fruit-bearing shoots, since these will be the most marginal fruit and thus will be parasites for resources relative to the fruit in better positions Any shoot that ends in a cluster (which is an indication of weak previous season growth) should be cut back to some vegetative shoots. Both of these decisions have the most positive impact if pruning is done when dormant
  
• After removing those parasitic fruiting sites, where there is still excessive crop, a gloved hand run along the underside of the overset branches can help remove fruiting spurs to space the remaining crop out some; again, best done from budswell through bloom
  
• Some cultivars usually have a lighter crop (e.g., 'Cavalier' and 'Regina' in Michigan) and it is a fine problem to have a larger crop
  
• Final possible attempt is to cluster thin, just reaching into heavy set sections and ripping off handfuls of fruit. A general target could be to have no more than about 35 fruit per linear foot of branch on average across the length of a branch (no data on that, just an estimate)
  
• Cultivar selection is important, perhaps self fruitful trees should never be planted on Gisela 5 and 6. Vandalay and Tehranivee (self-fruitful cultivars developed at Vineland) always set too heavy to the point that growers have given up and removed trees. However, fruit from trees using standard Mazzard have performed well and yielded medium to large fruit
  
• Do not let the trees become stressed - irrigate, mulch, thin if necessary - early
  
• The late Gus Tehrani used to recommend spur pruning on pears if they were stunted or had poor growth, the same should be done for sweet cherries

Lindsay Hainstock, invited speaker from Okanagan, British Columbia packing house, presented her talk on "Growing Large Sweet Cherries" at the Ontario Fruit and Vegetable Convention in February, 2008. Most of the pictures that she had of poor, "runted out" orchards were unfortunately typical of many Ontario dwarf sweet cherry orchards. In fact, dwarfing rootstocks were not the first choice in British Columbia where annual cropping is more consistent than in eastern North America and where self-fertile cultivars like 'Lapins' and 'Sweetheart' dominate the cultivar mix.

You can never have excessive vigor on a Gisela tree - if growers had good vigor last year, it is a good sign that they may be able to achieve annual balanced crop loads to manage this bounty well! .