Selecting Stone Fruit Crops and Varieties - Growing Organic Orchard Fruits - page 261

these rootstocks for large, commercial orchards. Gisela 12 (80 to 90 percent
of standard size) comes from the same rootstock program. Newer pruning
techniques, described in chapter 12 ➔ , have been developed to help main-
tain fruit size on these highly productive rootstocks.
Krymsk 6 (65 to 70 percent of standard size) and Krymsk 5 (85 to 90 per-
cent of standard size) from a Russian breeding program are seen, by some,
as replacements for the Gisela selections. According to the research sta-
tion where these selections were developed, the Krymsk rootstocks are com-
patible with sweet and tart cherries, encourage wide branch angles, provide
good adaptation to cold climates and wet soils, and produce early bearing
and good fruit size. There needs to be much more testing on these and oth-
er dwarfing cherry rootstocks, however, before we have a clear picture of
which rootstocks are best for particular cherry varieties, training systems,
and growing regions.
For small commercial, market, and home orchards, your best results will
probably come from the use of Gisela 5, Gisela 12, or Gisela 6 (in order of in-
creasing tree size). Of the three, Gisela 6 appears to be somewhat more com-
mercially accepted. Trees on Gisela 5 should be supported, and supports are
also often recommended for Gisela 12 and Gisela 6. Krymsk 5 and Krymsk 6
appear worth testing. Weiroot 72 rootstock produces very small cherry trees
about 6 to 9 feet tall, but it requires excellent soils and growing conditions, as
well as support for the trees. This rootstock is not likely to be used for com-
mercial orchards, but it could be valuable for home orchards where space is
limited.
Adara rootstock provides no dwarfing but is adaptable to heavy, poorly
drained, and calcareous soils. Likewise, Colt and Maxima 14 produce
standard-sized trees. Maxima 14 is precocious and can shorten the time from
establishment to harvest.
Pollination. With a few exceptions, sweet cherries are self-unfruitful and re-
quire cross-pollination. Unfortunately, many sweet cherry varieties do not
effectively cross-pollinate each other. Efforts have been made to cluster in-