Organic Gardening Tips and Methods Ornamental Trees (Part 8, Section 2) Pruning Established Deciduous Trees; Once a deciduous tree is well established, there is little need for further pruning; major pruning of a tree is best carried out by a tree surgeon or arborist, as the work is both skilled and dangerous and if poorly executed may ruin the tree. Many branched-head trees become over-crowded in the centre as they mature, restricting the amounts of air and light that reach the central branches, cut out any inward-growing shoots and any branches that spoil the balance of the framework. If a tree has grown too large for its situation, do not attempt to restrict size by heading back all new growth each year; this “haircut” pruning produces an unsightly, congested cluster of shoots each season which spoils the natural appearance and reduces the flower and fruit production. The correct treatment is as for the renovation of old trees, as a result of hard-pruning or the removal of large branches, a tree may produce a mass of epicormic or water shoots; rub or cut these out immediately. If the central leader is damaged, select a strong shoot close to the top of the main stem and train it vertically as a replacement leader, tie the selected shoot to a cane or stake secured high on the main stem and prune out any potential competing shoots. Once the shoot has developed into a strong dominant growth, the cane can then be removed. If a tree develops two or more competing leaders, remove all but the strongest shoot, the very narrow crotch angle between rival leaders is a source of structural weakness and the tree could split open at this point in a high wind. Vigorous upright shoots may develop on young, branched-head trees, if left, these will quickly grow into competing leaders and so it is important to remove them entirely as soon as possible. Pruning Established Evergreen Trees; Broadleaved evergreens only need minimal pruning, provided that the trees have an established leader and that any badly placed laterals have been cut out when young, it is necessary to remove any dead, diseased, or damaged wood. Conifers require only basic pruning once established, except when they are grown as a hedge. On some Pines (Pinus), Silver firs (Abies), and Spruces (Picea), the terminal bud on the leader may die; if this occurs, train in the best placed lateral as a replacement leader and cut out any competing, upright shoots. Established palms require no pruning apart from the removal of dead leaves which should be cut back to the main stem. Root Pruning; If an established tree is growing vigorously, but producing very few flowers or fruit, pruning the roots may help to slow down growth and stimulate better overall performance. In early-spring, dig a trench just outside of the tree canopy, then; prune back any thick roots to the inner-edge of the trench, using a pruning saw, secateurs, or loppers, retain any fibrous roots at the inner-edge of the trench, back fill the soil and firm. In some instances, it may be necessary to support the tree with stakes or guy-ropes if it seems unstable afterwards. Pruning Container-Planted Trees; Container-planted trees should be pruned annually, following the same principles as for other trees, to regulate their shape and size, and to maintain a strong, balanced framework of evenly spaced branches. Coppicing and Pollarding; Coppicing is the regular pruning of a tree close to the ground to encourage strong, basal shoots to grow. Pollarding is the pruning of a tree back to the main stem or branch framework, stimulating new shoots at this level. Traditionally, both techniques were practised to give a regular supply of firewood or pliable stems for basketwork or fencing. Now they are used in gardens to enhance leaf colour and their size, or the colour of their ornamental stems, or to restrict the trees size. Coppicing; Trees should be coppiced in late-winter or early-spring; some Willows when grown for their coloured or glaucious stems, may be left until mid-spring, and pruned just before or very shortly after bud-break, cut back all stems to the base, leaving the swollen basal wood un-pruned as all new growth occurs here. Less vigorous trees should be coppiced over two years, cutting back half of the stems one year and the remaining old-ones the following year. Pollarding; To form a pollard, plant a young branched-head standard, when its trunk has reached 2m (6ft), or the desired height, prune back the branches to 2.5cm-5cm (1-2in) from the main stem in late-winter or early-spring, this results in a mass of shoots developing from the top of the cut stem, prune back the shoots annually (or every second year) to stimulate further young shoots to grow from the enlarged-head of the stem, thin them out if they become congested. Remove shoots that grow on the trunk as soon as they appear. To produce a pollard with a main branch framework, allow the tree to develop a well-balanced branch system at the desired height. In late-winter or early-spring, prune back the branches to about 2m (6ft), cut back the resulting, secondary shoots every two to five years (2-5yrs), depending on the species, until the pollard is established, thereafter, prune every year or two, and thin out the shoots as required, if too many enlarged-heads develop close together, cut some of them out entirely. Trees for Coppicing and Pollarding; • Corylus avellana “Contorta” **, • Eucalyptus dalrympleana, • E, globulus**#, • E, gunnii**, • E, pauciflora, • Populus x canadensis “Aurea”, • P, x jackii “Aurea”, • Salix acutifolia “Blue-Streak”, • S, alba var’ Sericea, • S, alba var’ Vitellina, • S, alba var’ Vitellina “Britzensis”, • S, daphnoides “Aglaia”, • S, Erythroflexuosa, • S, irrorata**, • Tilia platyphyllos (cvs), • Toona sinensis “Flamingo” • Note, ** = Trees for Coppicing only, # = Non-Hardy Trees Renovating Old-Trees; Trees that outgrow their situation, or that have been neglected, should be either removed and replaced, or renovated to return them to full health and vigour. Renovation requires considerable care and expertise and it is advisable to consult an experienced tree surgeon. In some cases, a tree may be too old and potentially dangerous to renovate, so it may be better to replace it, in others such as with old flowering cherries (and other Prunus’). Renovation is rarely successful because of the silver-leaf. Renovation may be undertaken at anytime of the year, except at the start of growth in spring; for most trees, however, and particularly those that produce a lot of sap, such as; Horse chestnuts (Aescules) and Birches (Betula), late-autumn or early-winter is the best time. The first stage is to remove all dead, diseased, and damaged wood, then prune out any crossing or congested branches and those that spoil the balance of the framework. It is best to carry out extensive renovation over two or three years to allow gradual recovery since drastic pruning may severely weaken or even kill a tree in poor health, if you need to remove any large branches, do this in sections. After renovating the tree, feed it by mulching with well-rotted manure and apply fertilizer to the ground beneath the tree canopy in spring for two to three years, hard pruning may stimulate the growth of a mass of side-shoots; if congested; thin some of them out to leave a well-balanced framework, any suckers and water-shoots should be removed as soon as they are noticed (or appear). Renovating “Haircut” Pruned Trees; Trees that have had all their new growth trimmed back annually produce a congested cluster of shoots every season on knobbly branches, but without the balanced framework of a true pollard. Such “haircut” pruning is unsightly and reduces flowers and fruit. To correct it, first, thin out the knobbly stumps at the ends of the main branches, then, cut out most of the young shoots on the remaining stumps to leave just one or two and cut these back by about one third (1/3rd): repeat this procedure in the following three or four seasons to develop a natural growth habit. Tree Surgeons; For pruning, renovation of large trees, it is advisable to consult a qualified tree surgeon, the nearest horticultural college or arboricultural association may be able to supply a list of approved consultants and contractors, who comply with required standards of safe working practices and technical competence (Health and Safety Guidelines/Health and Safety at Work Acts). Before inviting contractors to tender, decide exactly what work is required, including the disposal of any debris which may be the most expensive part of tree surgery operations, quotations are normally provided free, but a fee may be charged for advisory work that is/would be involved. Pleached Trees; Pleached or Plashed, trees are clear-stemmed trees planted in one or more rows with their branches trained horizontally to intertwine, creating a formal, raised “wall” of foliage when in leaf. Hornbeams (Carpinus) and Limes such as; Tilia platyphyllos, T, cordata “Winter-Orange”, and T, x euchclora make excellent pleached avenues as they can be clipped precisely and within four or five years, develop an effective, boxed appearance, it is best to use young trees with pliable stems when pleaching. Constructing the Framework; Until the trees are established, they should be trained in to a framework, first, using one stake for each tree to be planted; set up a row of 2.5-3m (8-10ft) high, stout-stakes an equal distance apart, once driven into the ground to a depth of approximately 60cm-1m (2-3ft), they should be at the required height of the lowest branches; at about 2m (6ft) or more if they are to allow people to walk/pass underneath, attach a secondary framework of wooden battens or wire (horizontally) to these stakes to create the desired overall height. Initial Training; Plant a young tree next to each stake in late-autumn or early-winter, choose trees that are sufficiently tall so that their laterals may be trained into the framework, after planting tie in the leader and laterals, pruning out any badly placed ones. Further Training; Throughout the growing season, pinch out all new shoots that cannot be trained sideways, tie in the leader as it extends and train along the top batten, tie in a suitable positioned lateral along the top batten on the other side of the main stem. In winter, shorten any long-laterals back to a strong-sub lateral, and cut sub-laterals back to two or three buds to stimulate new stems to cover the framework, continue to develop a boxed-effect in subsequent seasons by tying in branches and cutting back the laterals to stimulate new shoots and dense growth. Once the pleached trees are fully established and the branches have intertwined, the framework may be dismantled, maintain healthy, dense growth by removing any dead, diseased, or damaged wood and strongly growing laterals, rub out young shoots as soon as they are noticed (or appear). Note; All information given coincides with the Guidelines of The Royal Horticultural Society (RHS)....
Posted on: Thu, 11 Sep 2014 13:52:43 +0000