These notes were produced for the propagation staff at the Lost Gardens at Heligan and represent a reasonable process.

 

 

Lost Gardens of Heligan

Camellia Propagation

 

The Gardens (which, for completeness, also include those of Heligan House) contain a significantly important historical collection of the varieties of Camellia japonica. The first group of these plants was probably introduced to the Garden by JH Tremayne but the majority represent the plantings of John Tremayne sometime during the 1860s or 1870s. This latter group includes some very unusual and rarely seen vari- and parti-colour flowered varieties in which shades of red and pink appear as ‘broken’ colours on a white background. The names and descriptions of these varieties have been found in the Verschaffelt catalogues of the period and have circumstantially been confirmed from other sources of the same period as being in commerce in the UK.

 

It is very unusual (even very rare!), nowadays, to find these varieties in cultivation and putative identification and verification of their names is distinctly circumstantial. We have not found any expert source which is prepared to identify the greater proportion of these varieties absolutely. All that we do know derives from the indefatigable efforts of Bee Robson who has tracked down the most likely sources and derived the potential scenario for their presence at Heligan. This group therefore represents an interesting and significant collection which requires to be propagated not only to secure the potential for replanting but also for the wider distribution of these plants for posterity.

 

The key to successful propagation and crop production will be the establishment of correctly named and properly maintained stock plants - so that naming and provenance can be relied on and so that productive propagation techniques can be applied.

 

A suitable (stock plant) site needs to be allocated for this purpose as the quantities of productive propagation material needed will be substantial - if the crop numbers required for a retail promotion annually are to be worthwhile. An open ground, sheltered site would be ideal.

 

Now that these plants have been effectively named and described, there is a major opportunity for their exploitation.

 

The Propagation of Camellia japonica cvs

by leaf bud cuttings

 

The successful micro-propagation of Camellias is currently not available - despite the best efforts of the Rosewarne Project. However one day success will be achieved. This implies that conventional propagation techniques are still the best option.

 

The success of any method of propagation depends on treating the process as ‘a crop’ – ie to deliver significant numbers. This should engender a detailed and analytical approach with a proper consideration and management of the whole process.

 

The propagation of Camellia japonica cvs is most effectively and economically achieved by means of Leaf bud cuttings.

 

* Leaf bud cuttings are single node cuttings which are made from the current season’s growth, when the majority of leaves are fully expanded (July to September in Cornwall).

The stem system of the ensuing plant derives from the extension growth of the single bud in the leaf axil; normally root initiation and development of the root system derives from the existing stem, although subsequently roots may well develop from the base of the new stem growth.

 

* The sooner in the season that propagation can be initiated the better as it is beneficial to achieve some stem growth (however minimal) before the onset of dormancy. This creates an ‘integrated plant’ rather than a ‘rooted cutting’ before dormancy. The development of this crucial physiological status can significantly affect the timing and uniformity of bud break during the following Spring (and hence uniformity of crop production).

 

* The production of sufficient cutting material of a useful regenerative capacity depends on the availability of suitably maintained and judiciously pruned (hard pruned) and managed stock plants. The vigorous, upright, annual growth, so produced, should yield six to eight, sufficiently mature, propagules per stem.

 

* The individual identification of the varieties and its successful maintenance is of paramount importance to the process of this type of specialist crop production.

 

In general the propagation and production of the varieties of Camellia japonica is a relatively simple and productive process if reasonable attention is paid to the detail. The only proviso in this case is the age of the varieties – age bringing a lower regenerative capacity. However the establishment of new young stock plants would go some way to mitigating this.

 

The Process

 

The leaf bud cuttings are made approximately 40mm long. Cut obliquely just above a bud and make the basal cut more or less horizontally. There should be no need (in general) to reduce the leaf area.

 

Keep all cuttings labelled – do not put more than one variety in each container.

 

The cuttings are inserted vertically into the compost so that the base of the bud is at, or about, soil level (see above).

 

Camellia japonica cvs are not fast rooting – so the process will normally take several weeks.

 

If the cutting material derives from suitably maintained stock plants - the vegetative vigour of the material should produce a high level of regenerative capacity and no treatments should be necessary. However there is no reason why the cuttings should not be treated with a hormone rooting powder to the cut surface of the base (only). Any type of wounding is unlikely to be effective unless the material is from particularly old, untreated plants.

 

It would be prudent to insert the cuttings into a conventional container (such as a plastic seed tray) as the management of the water status of the compost will be easier and more reliable than if a modular system is adopted.

 

The cuttings should be inserted into a well drained compost (50/50 peat/sand or equivalent) which fills the container more or less to the top (relate to the length of the cutting!).

 

The number per tray will be a function of the leaf size but would probably be somewhere in the order of 40 per tray (ie 8x5) but as high a density as is feasible - as productivity is the key.

 

Ideally it would be sensible to water in with an application of a suitable fungicide.

 

The containers are then placed on a propagating bench with a bottom heat of 20̊C.

 

The containers should be covered with a very light grade of polythene (Dry Cleaner grade!) and provided with adequate shade (to avoid potential scorching).

 

Mist is not an essential feature in the propagation of Camellias and, because of the length of time involved in the rooting process, can be counterproductive - because of the leaching of soluble materials from the leaves.

 

Clean the benches with Jet5 to eliminate algal growth before setting out the containers.

 

Maintain normal good practice in the propagating area.

 

When the cuttings are sufficiently rooted they should be weaned and maintained, under protection, over winter. It is important at this stage to provide an environment which will encourage the bud to break and grow – even if only marginally - before the onset of dormancy. It will be prudent to avoid overwatering during this winter. In practice they should be kept reasonably dry. However this does not imply complete drying but ‘just moist’ and this throughout the soil profile. This would be best achieved by sitting the trays on capillary matting and critically monitoring the watering regime. If any substantial growth starts in the late summer / autumn then the trays should be watered with a dilute liquid feed while it is still warm enough for growth to occur.

 

As soon as growth appears to be starting in the late Winter to early Spring the rooted cuttings should be potted up into liner pots using an ericaceous compost and encouraged into growth under protection (ie a polythene tunnel) until it is deemed that they are sufficiently well established. At this stage they can be placed outside or potted on.

 

Continually monitor the condition of the plants and the growing environment and ensure that the plants continue to grow and thrive.

 

Keep detailed records.