Chronica Horticulturae volume 49 number 2 ... - Acta Horticulturae

Figure 2. Flowering Rosa rubiginosa. Photo: M. Uggla.
drought, but then the hips will be smaller.
Young plants can be damaged by rabbits or
deer, which should be considered when starting
a plantation, but once they have reached 75
cm-1 m, they are usually sufficiently armed with
prickles and bristles to deter any larger animal.
They have very deep roots, so if the plant
freezes to ground level during a cold winter,
new shoots will appear. Actually, once a
dogrose plant is established, it can be quite difficult
to remove.
ent shades of red depending on the species.
The leaves of roses are compound leaves, and
the dogrose species have seven to nine leaflets
on each leaf. The leaflets are more or less ovate
or elliptical with either simple or double serration,
and they could be glabrous or more or less
pubescent either beneath or on both sides. The
sepals on the hips could either fall off during
the maturation, or they could stay on. For commercial
purposes, the hips should preferably be
without sepals when they are ripe. The prickles
on the stems can be up to 20 mm long and
more or less curved or hooked and some
species also have smaller prickles interspersed
with the large ones. All these morphological
characters are important for species determination.
There is not one single character that can
separate the species from each other but
instead a whole set of them will have to be
used. The dogroses are notorious for their difficulty
of species delimitation.
one of the more severe weedy plants in the
area.
Dogroses are normally very hardy. They have a
large tolerance span in temperature and soil,
and they can grow in more or less pure sand to
clay, but sandy soil is the preferred choice
(Fig. 3). They can also tolerate longer periods of
Fruits and Seeds
In Scandinavia, rose hips ripen in the middle of
August until beginning of October, depending
on species and temperature. The hips do not
abscise from the plant, but can remain until
next year. It is therefore vital to know when it is
ripe to harvest as the vitamin C level peaks at
this point. This is estimated to be when the
orange color of the hip has turned into red and
remained constant for one week.
The hard-shelled seeds, called achenes, reside
inside the fruits called hips. The number of achenes
is usually 15-50 in each hip and they are in
deep dormancy when the hip is ripe. The seeds
have normally a low germination. Only a third
of all seeds ever germinate and these are spread
out over a number of years with the most germination
occurring during the second year.
Therefore, different pre-treatments with plant
growth regulators such as gibberellic acid have
been tried and shown to have a positive effect.
Also stratification with warm and cold temperature
has shown to increase germination.
Commercially, acidification is used and then
between 50-70% of germination can be
achieved after one year. In order to get a profitable
seed germination, the hips should be harvested
when they are ripe and not linger on the
Figure 3. Rosa canina growing among the pebbles. Photo: K. Rumpunen.
ECOLOGY
The dogroses are colonizing species, often
growing in disturbed areas such as roadsides
and open pastures. Their seeds have been
brought along to other continents than the
original Europe and Asia, and today they can be
found everywhere except the Antarctic or the
Arctic. At the end of the 19th century, one
species, Rosa rubiginosa, was introduced into
New South Wales in Australia as an ornamental
plant. Some decades later, it was regarded as
CHRONICA HORTICULTURAE •VOL 49 • NUMBER 2 • 2009 • 9