can be taken from stems that have attained different
stages of maturity. Hardwood cuttings
are from pieces of dormant
woody stem containing a number of buds, which grow out into shoots
when dormancy is broken in spring. The base of the cutting is cut
cleanly to expose the cambium tissue from which the adventitious
roots will grow (e.g. in rose rootstocks, Forsythia, and many deciduous
ornamental shrubs). In Hydrangea and currant the stems show evidence
of pre-formed adventitious roots (root-initials), which aid the process
of root establishment. Hardwood cuttings are normally taken in late
autumn (they are 15–25 cm in length), and are often placed with half
their length immersed in a growing medium containing half compost
and half sand. A 12-month period is often necessary before the cuttings
can be lifted.
are taken from stems that are just becoming woody.
They are normally taken from mid-summer to early autumn. Most
cuttings of this kind are 5–10 cm long. Rooting in a sand/compost
mixture may be achieved in cold frames or, more quickly, in a heated
structure at about 18°C. Eleagnus
(Oleaster) will root only if heat is
provided. Many shrub and tree species, e.g. holly and conifers, are
propagated as ‘heeled’ cuttings. Here, the semi-ripe cutting is taken in
such a way that a one centimetre sliver of last year’s wood (the heel
still attached. The heel cambium facilitates root formation and, hence,
easier establishment of cuttings.
Stems without a woody nature are used for the propagation of plants
such as Fuchsia, Pelargonium
These are called softwood cuttings
(see Figure 12.3), and they are most often taken in
late spring and early summer. The area of leaf on these cuttings should
be kept to a
|Figure 12.3 Rooted cuttings
minimum to reduce water loss. Misting (spraying the plants
with fine droplets of water to increase humidity and reduce temperature)
can further reduce this risk by slowing down the transpiration rate.
Automatic misting employs a switch attached to a sensitive device used
for assessing the evaporation rate from the leaves. The cool conditions
favouring the survival of the aerial parts of the cutting, however, do not
encourage the division of cells in the cambium area of the root initials.
The temperature in the rooting medium may be increased with electric
cables producing bottom heat . These special conditions for the success
of cuttings are provided in propagation benches in a greenhouse.
are also susceptible to wilting before the essential
roots have been formed, and will benefit from mist, provided the wet
conditions do not encourage rotting of the plant material. Leaves of
plants such as Begonia, Streptocarpus
into pieces from which small plantlets are initiated, while leaves plus
petioles are used for Saintpaulia propagation. Nursery stock species,
require a complete leaf and associated
axillary bud in a leaf-bud cutting.
may be an option when other methods are not seen to
succeed. This method is used for species such as Phlox paniculata
and Anchusa azurea (alkanet).
Roots about a centimetre in thickness are
taken in winter and cut into 5 cm lengths. They are inserted vertically
into a sand/compost mixture in most species, but thinner-rooted
species such as Phlox
are placed horizontally. It is important that root
cuttings are not, inadvertently, placed upside-down, as this will prevent