Page 44 - Green knowledge 2025

Photo: Hege Ulfeng
Good apple trees start underground
An apple tree is in fact two trees. The root, or rootstock, comes from a completely different
variety than the trunk and branches. When a rootstock and a main variety are combined, it
is called grafting. The rootstock not only determines how large the tree can grow, but also
how many years it takes before it bears fruit, how the tree adapts to different soil
conditions, and how well it tolerates cold.
NIBIO research scientist Dr Darius Kviklys is an
expert on rootstocks. He coordinates a European
trial programme under the auspices of EUFRIN
(European Fruit Institutes Network), where the
focus is apples.
The rootstock is crucial for successful apple cultiva-
tion.
“It influences the uptake of water and nutrients and
is important for the hormonal balance of the entire
tree. This has consequences for both yield and qual-
ity,” explains Dr Kviklys.
The rootstock and the variety must be suited to each
other. Too weak a rootstock for low-vigour varieties
gives poor results. Conversely, vigorous varieties on
a strong rootstock can produce very large trees.
In professional cultivation, almost only weak root-
stocks are used. The trees must be supported and
carefully managed to grow well. In return, they pro-
duce early and high yields with much less labour
input than larger trees.
“Low-vigour trees are more sensitive to pests. Stron-
ger trees will survive an attack better and recover.
They can also compete better with weeds for both
water and nutrients because they have a more exten-
sive root system,” explains Dr Kviklys.
In Norway, as in almost all apple orchards in West-
ern Europe and the USA, a rootstock called M.9 is
used. It was developed in England around 100 years
ago. One of its disadvantages is that it is not particu-
larly winter hardy, which is important for Norwegian
apple production.
At present, NIBIO is involved in testing 24 different
rootstocks.
Purpose: Funding: Contact: Improved rootstocks for apple trees.
EUFRIN (European Fruit Institutes Network)
Research Scientist Darius Kviklys, Division of Food Production and Society.
Email: darius.kviklys@nibio.no | Phone: +47 413 24 561
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