I believe on many reclamation sites the use of very tall rooted planting stock, such as TRS Cuttings, will improve re-vegetation success – as opposed to using smaller rooted nursery stock or larger unrooted live cuttings. Several example situations are given here.
1) In shoreline areas with large seasonal water level fluctuations (e.g., reservoir draw-down zones). Here keeping plant tops above water during peak flood periods is critical for survival and establishment.
2) In areas with dense herbaceous weed cover. Planting tall trees and shrubs here will immediately put the weeds in the understory, and therefore at a competitive disadvantage. TRS Cuttings therefore represent an important weed management tool.
3) On sites that dry out rapidly after an initial moist period in the spring – using plants with an established root system with be advantageous over using unrooted cuttings. The large stem length of TRS Cuttings also means the root ball can be planted very deep, up to 1.5 m or more. By doing so survival on such sites may be improved.
4) In areas with ungulate populations planting very tall sturdy plants may put new shoots out of the reach of these browsers. Note: To prevent damage to lower stem portions protective measures can be applied to the plants themselves — see Protecting your plants in the field.
With these points in mind the advantages of TRS Cuttings are discussed below, first with respect to with respect to standard unrooted live cuttings, and second with respect to standard potted nursery stock.
1) Advantages of TRS Cuttings with respect to standard unrooted live cuttings.
Improved Survival and Establishment
Because TRS Cuttings already have roots, their establishment is substantially advanced over standard unrooted live cuttings. With the latter there is a time-lag of perhaps several weeks, or longer, between planting and the development of a substantial root system. On some sites this can result in mortality of the cuttings due to drought stress or desiccation before sufficient roots can form.
On sites with high levels of competing herbaceous vegetation the presence of a root system will also shift the competitive balance in favor of the trees and shrubs, favoring their successful establishment.
The added per-unit cost of rooted TRS cuttings, above that of standard unrooted live cuttings, may therefore be offset by better survival and overall reclamation success. Also, fewer cuttings may be needed to achieve the desired goals.
Planting can be done during the late summer and early fall (within fisheries work windows).
TRS Cuttings started in the spring usually have sufficient root development to allow for out-planting by mid-August to mid-September – of the same year! This is a good time to plant in riparian areas (especially within the “capillary fringe“) as it fits within many fish “work windows.” (The annual period each year when you are allowed to do construction work next to streams).
In southern BC the fish “work windows” for in-stream construction work (legislated), although varying depending on location and species of fish, generally start around late June and run into October – See B.C. Ministry of Environment, Regional Timing Windows.
This is not a period when the use of standard unrooted live cuttings is generally feasible, as these are best collected when the plants are dormant (in BC between about late October and the end of March).
Reservoir draw-down zones and other seasonally flooded areas
One environmental zone for which tree and shrub establishment is often difficult or impossible is the draw-down zone of reservoirs and some other seasonally flooded areas. This is because these areas are completely submerged under water for a portion of the year, but also often have very dry soil conditions during the periods not inundated.
To minimize water loss from a standard (unrooted) live cutting it is standard practice to use cuttings 0.8 to 1.2 m long and plant them with about 80% of this length in the ground. However, the small above-ground portion resulting from this (e.g., 20 cm) can be a problem in situations where complete inundation occurs. This is because complete submersion of live cuttings for an extended period during establishment will result in mortality.
Depending on the shoreline planting elevation – where inundation does occur longer cuttings often have better survival, as this allows the tops to remain above water during peak flooding. For example, a 2.8 m long cutting would be planted with about 80 cm in the ground (the maximum depth normally practical), and 2 m above ground.
In such situations planting is usually done in the spring, before the reservoir level rises. Then, with spring snow melt the water level rises rapidly, to a maximum often occurring in May/June. However, there is often little root growth on the cuttings once flooding occurs, as the soil conditions become anaerobic and cold. Shoots do however sprout and grow during the flood period, feeding off the energy reserves within the cuttings themselves. But if these shoots become completely submerged for more than a week or so .. the plant will die – hence use long cuttings.
A problem with this approach, however, is these unrooted cuttings are susceptible to desiccation when water levels recede and the soil subsequently dries out, sometimes quite rapidly – as there has been little root growth.
Because TRS cuttings already have roots these plants are much more resistant to drought conditions when water level recedes. I believe this may enable the establishment of trees and shrubs at lower elevations around some reservoir edges. Experience has also shown me this can be the case – TRS cuttings were used extensively in the Selkirk College Shoreline Restoration Project.
2) Advantages of TRS Cuttings with respect to standard potted nursery stock
It is not uncommon for nurseries to produce very large reclamation plants, established either from seed or cuttings – but this normally involves growing the plants for several years in a nursery and transplanting into large, cumbersome pots. Such pots may be up to 5-gallons in size, especially if a plant comparable in height and caliper to a 2 m+ tall TRS cutting is produced. Most rooted nursery stock used in reclamation is therefore comparatively small – usually no more that about 0.25 to 1 m in height.
With TRS Cuttings it is possible to produce very tall rooted plants in only one growing season – relying on the woody stem – but with a relatively small (e.g., 1 or 2-gallon size) root system. They are therefore efficient to transport and plant. Note that the shoots of TRS Cuttings can also be pruned to match the root system after out-planting, and so (depending on the site) the issue of an out-of-balance shoot:root ratio is easily avoided. In addition, because they are ready to plant after one growing season, the time required for the forward planning of reclamation projects is shorter.
Another advantage of their great size is with respect to community or school planting events; here a small “forest” is instantly created. This is very satisfying for those involved.