THE USE OF PEAT IN PROPAGATING HARDY NURSERY STOCK AT KINSEALY
Sphagnum peat is widely marketed as a commercial product, uniform in grade and composition. Sand, however, varies greatly according to its place of origin. In many districts in Ireland local deposits of sand are highly calcareous, and are considered very unsuitable for use in the propagation of nursery stock. Therefore a substrate containing relatively little or no sand is recommended to our growers unless trials have shown the need for a high sand content. Other factors favouring the use of peat include its lightness in the rooting containers and on the glasshouse bench, and the ease with which cuttings can be transplanted with peat adhering to the roots. Results are recorded on the basis of the numbers of cuttings rooted as a percentage of the number inserted, and the quality of the roots obtained. Quality of rooting is assessed on the numbers of roots, their length and their ability to withstand transplanting without breaking.
Sphagnum peat ("peatmoss") is recommended for many genera belonging to Ericaceae e.g. Rhododendron (table 1).
Although in this instance there is evidence that the addition of one part of sand (washed river sand of granitic origin) gave quicker rooting, the convenience of using peatmoss alone is considered to be the greater consideration. Peatmoss is used at Kinsealy as the standard rooting substrate for cuttings of Sarcococca, Cytisus, Ilex and Hamamellis as well as for ericaceous plants.
A mixture of two parts peatmoss with one of sand is recommended for rooting cuttings of a wide range of trees and shrubs, e.g. Chamaecyparis (table 2).
The cuttings were inserted on April 4 and lifted on June 11. The numbers of ball-rooted cuttings are given in parenthesis (i. e. cuttings that lifted with so much compost that individual roots could not be separated). The results from sand were significantly poorer at the 1% level from 2 peat 1 sand and 2 sand 1 peat. Though the results were not shown to be significantly different from the mixtures with sand, the roots in this medium were brittle and easily broken at transplanting.
Other genera for which 2 peatmoss to 1 of sand is recommended, either from the results of trials or on an observational basis, include Thuja,