It would seem that the plashes or plushes, that fronted the fort at Ryde, were a form of what would later be called an abattis. Basically the idea behind plashing a hedge is to form a wattle-like fence of thickly interwoven and intertwined stems and branches, that will act as an impenetrable barrier to both cattle and human. Indeed, it can be seen as a sort of natural barbwire, a 'living palisado'. To strengthen the barrier's deterrence, thorn plants were used such as hawthorn [quickthorn], blackthorn, firethorn or holly. In a seaside environment, salt tolerant species such as buckthorn, sea buckthorn, willows, broom, wild roses, or gorse were available. Plashing was done either in October or February. It consisted of cutting off much of the side growth from the main stems and then cutting part way through the stem, bending it down slantwise, while inter-twining it among prepared upright stakes. Lying in a parallel, diagonal aspect, the plashes form a sort of closed lattice. As new side shoots grow upwards again, the hedge develops both rigidity and impenetrability. A series of well-plashed rows obviously presented a formidable living barrier to an enemy and either stopped an advance or hindered it enough to enable the defenders to bring deadly fire onto an enemy now caught in the open.

Plashed hedges also performed an environmental role in coastal protection by acting as a sand fence to trap blown sand and so build up the level of the shoreline in that area. This provided added physical protection for the fort and adjoining strip of land.

A plashed hedge showing the thick, woven barrier presented by the plashes.

The cut made in the stem to form a plash. The cut does not penetrate right through but leaves a small part of the sapwood and bark connected.

An exaggerrated example of the result of allowing a hedge to grow unmanaged. This hawthorn hedge has been allowed to grow naturally for a very long time and consequently huge gaps have opened up at the bottom.

An image from an 18th century handbook showing a section of completed plashing.

The booke of husbandry, John Fitzherbert. London, 1573.

To plash or pletch a hedge
If the hedge be ten or xii yeares growyng sith it was first set, then take a sharpe hatchet or a hand byl, and cut the sets in a plaine place nye unto the earth the more halfe a sunder, and bend it downe toward the earth, and wrap and winde them together, but alway see that the top lye hier then the roote a good quantitye, for els the sap wyll not run into the top kyndly, but in proces the top wyll dye, and then set a litle hedge on the backe side & it shal nede no more mending many yeares after, and if the hedge be of xx, xxiiii or xxx yeares of age sith it was first set, then wynd in first all the neather most bowes & wind them together & then cut the sets in a playn place a litle from the earth the more half a sunder, & to let it bend downwarde & not upward for dyvers causes, then wynd the bowes & branches therfore into the hedge, and at every two or three foote to leave one set growyng, not platched, and the top to be cut of four foote hie or therabout, to stand as a stake, if ther be any suche, or els to set another, and to wynde the other that be platched about them. And if the bowes wyll not lye playne in the hedge, then cut it the more halfe a sunder, & bynde it to the hedge, and then shall he not nede for to mende that hedge but in few places xx yeares after or more: and if the hedge be old and be great stubbes or trees and thyn in the bottom that beastes may go under or betwene the trees, then take a sharp axe, & cut the trees or stubs that grow a foote from the earth, or therabout in a playn place within an inch or two inches of the side, & let them slant downward as I sayd before, & let the top of one tree lye over the roote of another tree, & plech down the bowes of the same tree to stop the holowe places And if al the holow & void places wyll not be filled and stopped, then scoure the olde ditch and cast it up new, and fil with earth all the voyde places, and if so bee these trees wyl not reach in every place to make a sufficient defence, then double quickset it, and ditch it new in every place that is nedefull, and set a hedge thereupon, and to over laye the sets for eating of sheepe and other cattel.

The second booke of the English husbandman, Gervase Markham. London , 1614.

Part II, ch. VI. Of Plashing of Hedges
Know then that if after your hedge is come to sixe or seauen yeeres of age, you shall let it grew on without cutting or pruning, that then although it grow thicke at the top, yet it will decay and grow so thinne at the bottome, that not onely beasts but men may runne through it, and in the end it will dye and come to nothing, which to preuent, it shall be good once in seauen or eight yeeres to plash and lay all your Quick-set hedges, in which there is much fine Art and cunning to be used. For this plashing is a halfe cutting or deviding of the quicke growth, almost to the outward barke, and then laying it orderly in a sloape manner, as you see a cunning hedger lay a dead hedge, and then with the smaller and more plyant branches, to wreathe and binde in the tops, making a fence as strong as a wall, for the roofe which is more then halfe cut in sunder, putting forth new branches, which runne and entangle themselues amongst the olde stockes, doe so thicken and fortifie the hedge, that it is against the force of beasts impregnable.

Now to giue you some light how you shall plash a hedge, though diuers Countries differ diuersly in those workes, yet as neere as I can I will shew you that which of the best Husbandmen is the best esteemed. First, for the time of yeere either February or October, is passing good, and the encrease of the Moone would likewise be obserued.

For the tooles which you shall imploy, they would be a very sharpe nimble Hatchet, a good Bill, and a fine pruning knife. Now for the worke you shall enter into it, first with your Bill you shall cut away all the superfluous boughes, and branches which are of no use, or hinder your worke, and then finding the principall stemmes which issue from the maine roote, you shall within a foote or lesse of the ground with your Hatchet, cut the same more then three quarters through, so as they may hang together by nothing but the outward barke, and some part of the outward sap, and this stroke must ever be sloape-wise and downeward: then take those mayne bodies of the Quicke set, so cut, and lay them sloape-wise from you, as you would lay a dead hedge, and all the branches which extend from those bodies, and would spread outwardly, you shall likewise cut as before said, and fould them artificially into your hand, and euer within a yard or two distance, where a pretie Plant growes straight up, you shall onely cut off the top equall with the height of your hedge, and so let it stand as a stake, about which you shall folde and twind all your other branches. Now when you come to the top of the hedge, which would commonly not be aboue fiue foote high, you shall take the longest, youngest, and most plyant boughs, and cutting them as afore-said gently binde in the tops of all the rest, and so make your hedge strong and perfect: and herein is to be noted, that the closer, and thicker you lay your hedge (so there be nothing in it superfluous) the stronger and better lasting it will be. Many vse not to binde in the tops of their plasht hedges, but onely to lay the Quick-set and no more; but it is not so husbandly, neither is the hedge of any indurance: many other curiosities there be in the plashing of hedges, but this which I haue alreadie shewed, is sufficient both for the Husbandmans benefit and understanding.

A compleat body of husbandry. Thomas Hale. Vol. 1 Dublin, 1757.

Of Plashing a Hedge
... but among the rest he must consider, that he is to reserve some Shoots for laying down, and others to serve by way of Stakes. For the first Purpose he is to select those which are longest, and freshest; and such as are of a middle Growth : for the Stakes, he is to leave such as are somewhat larger, and stand properly, and grow tolerably strait for the first five or six Feet : it matters not for the rest, because they are to be cut off at that Height, their Use requiring no more.

When the Husbandman has thus considered, let him go to work. He is to cut away all the old Stubbs within two Inches of the Ground, striking them off sloping. After this let him go on thinning his Hedge, by cutting away all but the proper Shoots for Stakes, which he is to strike off at the Height he designs his Hedge, and the long Shoots for laying, which he is to leave entire.

As there will not be enough of these Shoots for Stakes, growing as they should do; he must make some others to drive into the Ground, where there is a Deficiency.
The Ditch is now cleaned, the Bank repaired, and the Stakes ready. Let the new ones be well and firmly driven, where there are not a sufficient Number of the upright Shoots left for thar Purpose : and these being disposed, the Work is ready for the Plasher.

He is to take each of the long Shoots which are left standing severally, and bending it gradually he is to give it a sloping Cut with his Bill, half through; it will then fall easily, and he is to weave it in between Stake and Stake carefully.

When he has thus worked in all the Shoots left for that Purpose, he is to go over his Work, and trim off the straggling Sprigs, to render it uniform and even.
if the Plashes are not too deep cut, and are laid thus evenly, or nearly upon a Level, or nearly upon a Level, the Sap is not all directed to their Ends, but sends up Shoots from every Part.

This Abundance of young Shoots will also be promoted by the proper cutting of the Branches of the plash'd Boughs. They are to be cut off short, at five or six Inches length on each Side of the Hedge; and this will make them send out Side Shoots of their own, as well as promote the Growth of the others, to the great Beauty and Strength of the Hedge. Many have a Custom of making their Hedges too high; but this is wrong for several Reasons. Let the Bank be raised carefully and firmly; and let the Hedge

Essays relating to agriculture and rural affairs, James Anderson. Edinburgh & London, 1777.

Of recovering old open Hedges by Plashing. It sometimes happens, that a hedge may have been long neglected, and be, in general, in a healthy state, but full of gaps and openings, or so thin and straggling, as to form but a very imperfect sort of fence. On these occasions, it is in vain to hope to fill up the gaps by planting young quicks; for these would always be outgrown, choaked,and starved by the old plants: Nor could it be recovered by cutting clear over by the roots; as the gaps would still continue where they formerly were. The only methods that I know of rendering this a fence are, either to mend up the gaps with dead wood, or to plash the hedge: Which last operation is always the most eligible, where the gaps are not too large to admit of being cured by this means.

The operation I here call plashing, may be defined, 'a wattling made of living wood.' To form this, some stems are first selected, to be left as stakes, at proper distances, the tops of which are all cut over at the height of four feet from the root. The straggling side-branches of the other part of the hedge are also lopped away. Several of the remaining plants are then cut over, close by the ground, at convenient distances; and the remaining plants are cut, perhaps half through, so as to permit them to be bent down almost to a horizontal position, and interwoven with the upright stakes, so as to retain them in that position. Care ought to be taken, that these be laid very low, at those places where there were formerly gaps; which ought to be farther strengthened by some dead stakes, or truncheons of willows, which will frequently take root in this case, and continue to live. And sometimes a plant of eglantine will be able to overcome the difficulties it there meets with, strike root, and grow up so as to strengthen the hedge in a most effectual manner.

The operator begins at one end of the field, and proceeds regularly forward, bending all the stems in one direction, so as that the points rise above the roots of the others, till the whole wattling is compleated to the same height as the uprights; after which it assumes an appearance somewhat resembling that which is represented in Fig. 5.

Cyclopędia: or, an universal dictionary of arts and sciences, E. Chambers. London, 1778-1788. Vol. 3.

PLASHING, a term used by our farmers to express an operation performed at certain times upon their quickset hedges, in order to assist their growth and continuance. This operation is performed sometimes in October, but more usually in February; and this is by much the better season for it. Suppose a hedge to be of twenty or thirty years growth, and full of old stubs as well as young shoots : this is the kind of hedge that requires plashing most of all.

The old stubs must be cut off within two or three inches of the ground, and the best and longest of the middle-sized shoots must be left to lay down. Some of the strongest of these must be left to answer the purposes of stakes. These are to be cut off to the height at which the hedge is intended to be left; and they are to stand at ten feet distance one from another: when there are not proper shoots for these at the due istances, their places must be supplied with common stakes of dead wood. The hedge is to be first thinned, by cutting away all but those shoots which are intended to be used either as stakes, or the other work of the plashing: the ditch is to be cleaned out with the spade: ...
In the plashing the quick, two extremes are to be avoided; these are, the laying it too low, and the laying it too thick: this makes the sap run all into the shoots, and leaves the plashes without sufficient nourishment into the plashes, and so makes the shoots small and weak at the bottom, and, consequently, the hedge thin. ...
When the shoot is bent down that is intended to be plashed, it must be cut half way through with the bill: the cut must be given sloping, somewhat downwards, and then it is to be wound about the stakes, and after this its superfluous branches are to be cut off, as they stand out at the sides of the hedge.

The practical planter, or, a treatise on forest planting: comprehending the culture and management of planted and natural timber, ... also, on the culture and management of hedge fences, and the construction of stone walls, &c. By Walter Nicol. Edinburgh, 1799.

Plashing is an operation more or less understood by every country man, bred in an inclosed district. The common method is briefly this:- The stronger stems are selected, at as regular distances as possible, and generally at about thirty inches apart. These are called the stakes; and are commonly headed over at four or five feet above the surface, according to the general strength of the hedge in question, so as they may all range in line, and at one height. The more pliable branches and small twigs are interwoven, in the basket manner, among the stakes, from top to bottom, as closely as possible. Such as will not bend, in a pliable manner, and aftrewards remain in due position, are snagged half-through with the bill, to make them more obedient. The strong stems, that cannot be laid in, and are not wanted for stakes, are cut close by the surface. In places where stems strong enough, and fit for stake, are wanting, the deficiency is supplied by dead stakes. After the plashing is finished, the hedge is dressed smooth on both sides with the bill, shears, &c.

We can have no reasonable objection to this mode, which is certainly the cheapest and most easily performed; except that the stakes, or cut-over stems, shoot forth strongly, to the detriment of the under part of the hedge, which, by over-shadowing, they retard in growth, and keep naked of spray.

This probably suggested improvement, which I have seen, namely, cutting none over at all, but weaving in the tops of the stakes along with the plashers. The propriety of this mode is at once evident; for, besides that the above complaint cannot possibly attach in this case, the stems cut by the surface send up a strong growth, which, intermixing with the plashers, renders the whole more close and impenetrable.
Plashing, however, can only be effectively and handsomely performed in cases where there is a good portion of spray and long pliable shoots or branches; and when the hedge has, if not youth, at least vigour on its side, to send forth a luxurious growth, and cover the naked appearance the plashers would otherwise have. For the more handsome performance of this business also, there is a season mor suitable than another, viz. the fall, or beginning of winter. At this season, the shoots are more pliable than in spring, when the sap begins to rise and circulate; at which time the shoots of all plants are most brittle.