Roadside Revegetation

IMPLEMENTATION GUIDES
Inset 10-22 | When should seedlings or rooted cuttings be substituted for live cuttings?
Live cuttings are widely used in biotechnical engineering projects.
Sometimes, however, it is more practical to substitute rooted cuttings
or seedlings in place of live cuttings. This is especially the case when
the road project calls for cuttings to be planted in the summer or fall,
when dormant, live cuttings are not available, or when live cutting
material is not available in large enough quantities.
For example, a road near a wild and scenic river is being widened.
Biotechnical engineering techniques using live willow cuttings are
being planned for retaining walls to increase slope stability in areas
adjacent to the river. The design looks good on paper (A). However
when discussing the details with a revegetation specialist, question
arises: where will the cuttings be collected and what time of year will
the willows be installed? Upon inventorying the willow stands on
the district, they learn there is not a supply of willows great enough
to meet the needs of the project. To obtain this volume and size of
cuttings would require the establishment of stooling beds at a nursery
(see Section 10.2.5, Nursery Cutting Production), which would take at
least two years prior to project implementation. More disturbing, they
learn that the contract can only be implemented in the summer due
to water quality and wildlife restrictions. While some cuttings installed
in the summer would sprout, most would not, as was determined
through rooting potential testing (see Section 10.2.2.4, Determine
Rooting Potential). Referring back to the project objective, the design
engineer and the revegetation specialist realize that going ahead
with the project, as designed, would compromise revegetating the
retaining wall. The decision was made to adopt an alternative design
to install rooted cuttings grown in long tubes (at a nursery) instead of
unrooted cuttings. The rooted cuttings would be planted at very high
densities where the brush layers were to be installed (Figure B). Since
only a small amount of cuttings would be necessary to start rooted
cuttings in containers at the nursery, there was no need to develop
stooling beds, eliminating the extra time and costs to produce these
plant materials.
The stems of the long-tube rooted cuttings can be set back several
feet into the soil (see circle in Figure B) as long as a portion of the
foliage is above ground. This will add length to the rooting area and
the stems will initiate roots (C).
A B C
Collection – Materials for live layering are obtained from branched cuttings collected in the
wild or from stooling beds. Stems up to 2 inches in diameter can be used (Sotir and Gray 1992).
The basal end of the cuttings are always oriented in the same direction during collection
and bundling. Cuttings for brush layers should be long enough that the growing tips are just
exposed at the soil surface, while the basal portion of the cuttings reach to the back of the
bench (Sotir and Gray 1992). For rock gabions, rock walls, and crib walls, cuttings should be
long enough to extend into soil or backfill behind the structures. During collection, cuttings
are placed in bundles and secured with twine. Bundles should be light enough to carry. The
optimum period to collect cuttings is during the dormant period, when the plants have lost
their leaves. If cuttings are collected outside of this period, then testing the viability of the
cutting material is essential (see Section 10.2.2.4, Determine Rooting Potential). Fine branches
dry out quickly if exposed to warm dry temperatures. Cuttings must be protected during
transportation, storage, and handling to avoid drying.
Storage – See discussion under Live Stakes, Section 10.3.3.2, Live Stakes.
Installation – Branched cuttings are laid out on benches so the basal end of the cutting reaches
to the back of the bench and the growing tips extend just beyond the front. Soil is placed
over the cuttings and tamped to assure there are no large air spaces. Excessive compaction is
unnecessary for plant establishment and is often detrimental for long-term plant growth (see
Section 5.3.3, Soil Structure). The material used to cover live branches in or behind crib walls,
rock gabions, and rock walls is often low in water-holding capacity, nutrients, and organic
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
353