Layer, a method used by gardeners to propagate some plants and many trees. After sowing, layering is generally the most successful means of propagating woody plants: resinous trees, holm-oaks, and terebinths are practically the only trees which resist it in some way, for even if the layered branches are eventually made to put out roots the young trees rarely come on well. However, ‘marcotte’ refers to only one particular mode of multiplying plants by layering, whereas ‘layering’ refers in general to a means of propagating plants and trees by making their branches strike root without separating them from their stems. It is possible both to make branches take root without using the method known as ‘marcotter’, and to air layer them without stretching them out. [1] In order to make these differences clearly understood, I will explain the various methods of enabling branches to strike root. It is a most interesting gardening practice, and is often the only means of multiplying rare and precious trees.

There are four methods of making branches strike root, which are applied according to the position of the branches or the quality of the tree.

1. The first method consists of simply laying out branches which are long and low enough in the soil. The soil must be good, loose, and mixed with compost. A small trench is dug, somewhat shorter than the branch and about five or six inches deep. The branch is laid there and bent, and the trench is filled in to ground level. [2]

The branch is arranged and laid out so that the growing point, which is above the ground, is upright. If the branches are inflexible and spring back, they should be pegged down with a wooden hook, for the success of the operation lies in making the largest possible bend without breaking or barking the branch. [3] Then, the sap, finding the conducting tissue blocked by a point both of contraction and extension, is obliged to accumulate, form an excrescence, and throw out roots. The recumbent branch should be cut to two buds above the ground and watered frequently in dry weather. This simple method is suitable for trees which root easily, such as elms, limes, planes, etc.

2. When dealing with precious trees which take root slowly or with difficulty, one should use the method known as ‘marcotter’, which is applied to carnations. The branch is stretched out in the manner described above and an incision made immediately above the bend: to this end, one cuts and ruptures the branch between two nodes, halfway through the wood and approximately one or two inches along its length depending on its strength. A small piece of wood is placed in the incision to prevent it from joining together. When layering trees such as variegated holly and other evergreens, which do not take root again readily following transplantation, one should plunge the bend of the branch into a pot or gardener’s basket and then bury it in the ground.

3. However, this expedient does not work on every tree, notably tulip trees, red mulberries, Chionanthus, and Viburnum. In this case, when the branch is being laid out, it must be squeezed immediately above the bend with an iron wire using pliers, and several holes pierced in the bark at the bend using an awl. This binding wire causes an excrescence to form below the constriction, which inevitably leads to the formation of roots. Instead of using an iron wire, a section of bark approximately one inch wide may be cut and removed below the bend. It is true that this incision works equally well, but since it delays the success of the operation by weakening the action of the sap, I have always found the iron wire to be the simplist, most suitable, and most efficient device. However, some people recommend twisting the branch at the point of the bend. This is ill-advised in that it could cause the branch to perish, and is also impracticable when the branch is strong or the wood hard.

The best means of propagating a plant by layering is to layer it entirely, leaving only the most vigorous branches on the tree and preparing each branch in the manner described above, according to the nature of the tree. This is because the most delicate trees decay when several branches are layered at their bases.

4. Lastly, there are trees which seldom have branches at their bases such as the bull bay, or which cannot be layered entirely because they are in tubs or pots. In this case, one lays a tin funnel on the branch which is to root or makes an incision in the branch towards the middle of the funnel, which is then filled with good soil. In this position, frequent watering is obviously required. This is what is referred to as ‘marcotter’ the branches without laying them out. [4]

When the layered branches have rooted sufficiently, they are separated from the mother plant and placed in the tree nursery. We cannot stipulate a precise time for removing these branches: usually a year is sufficient and sometimes six months, but one may have to wait for two or three years, depending on the nature of the tree, the soil condition, and especially the degree of tending which it has required.

However, it is possible to give some indication of the most suitable season for layering: one should begin in autumn, as soon as the leaves have fallen, if the trees are deciduous and the ground is not clayey, low, or damp, in which case one must wait until spring. Another exception must be made for the hardiest evergreens, which should be layered towards the end of August or the beginning of September when their sap is no longer flowing. One should layer all delicate trees, whether they are deciduous or evergreen, in April when the weather is no longer cold or frosty.

We have observed that in hardwoods the young shoots root more readily, while the opposite is true of softwoods, of which the oldest wood roots the best.

One uses ‘coucher’ for trees, ‘marcotter’ for carnations, and ‘provigner’ for vines: for the latter, see Layered stock.

Notes

1. The verb ‘marcotter’ is here applied to two distinct modes of layering, but in which the branches are in both cases incised: the first is a method of ground layering which is described under point 2, while the second corresponds to air layering or marcottage.

2. This method of ground layering is called trench layering.

3. Pegs are also used in French or continuous layering, where chosen branches are secured and new shoots covered with soil as they appear along the stem (Huxley et al., 1992, iv.799).

4. This technique is known as air layering or marcottage.