GardenLine | Trees and Shrubs | Espalier

There are only a few situations where a horticulturist recommends pruning trees into forms other than their natural shape. One of these is known as espalier. Espalier is the art of training trees to branch in formal patterns usually along a wall, or on a trellis. The technique of espalier first became popular several hundred years ago in the walled Medieval gardens of Europe. Few or no fruit trees could be grown in these walled gardens because of the limited space available. However, by placing the trees along the garden walls and training them to grow in a more or less two dimensional form, trees could be incorporated into the garden with relatively little loss in growing area.

Gardeners in the more northerly regions of Europe soon found a second benefit from espalier. Where the climate was cool and summer short, the warm sunny microclimate directly adjacent to a south-facing wall permitted fruit trees to mature their crops in a season that would not have satisfied the needs of free-standing trees. South-facing walls warm early in spring, collect heat during the summer, and remain warm later into the fall.

A third benefit of growing fruit trees in an espalier form is that the open frame created permits excellent light infiltration, with all parts of the tree exposed to direct sunlight. This results in a higher level of flowering, greater fruit production, and better colour development on the fruit. In addition, picking fruit from an espalier tree is simple due to the small stature of these trees.

If you would like to espalier a fruit tree, those such as apple or pear which bear fruit on long-lived spurs are probably the best to start with. However, to be properly managed, these trees should be on dwarfing or semi-dwarfing rootstocks. When a particular type of apple is grafted onto a dwarfing rootstock, that plant will have leaves and fruit of normal size, but the overall size of the tree will be reduced. `Ottawa 3' is a dwarfing apple rootstock which gives a 50% reduction in tree size and is available on the prairies.

Stone fruits such as plums and cherries can also be espaliered, but many of these bear fruit on the shoots of the previous season's growth. This means that renewal pruning is necessary to ensure a continuous crop.

Choosing the Planting Site

By far the most desirable spot to establish an espalier on the prairies would be a south-facing wall that received full sun during the summer, but was shaded by an adjacent building in the winter when the sun is lower in the sky. Since this is a rather specific and rare requirement, you should try to find the place closest to these particular conditions. An east-facing wall or fence that will deflect wind and trap warmth is probably the next best site. South or west-facing walls that are fully exposed in winter leave the tree exposed to direct winter light and reflected heat from the wall. This can lead to drying and dieback of branches, but extremely hardy Siberian crabapples may be able to survive these conditions. A tree growing along a north-facing wall will receive inadequate light, and will never flower or bear fruit to any extent.

Espalier Design

There are a few basic designs used in espalier. A T-shaped design has strong horizontal branches and results in a tree that looks somewhat like a very short telephone pole with several cross- arms. A cordon forms a tree that looks like a Jewish menorah, while a fan design is similar but less formal. The easiest design is probably an informal espalier where branches are not forced in any particular direction, or forced to become symmetrical with others, but are simply trained along a wall. Apple trees are usually trained as T-shapes or cordons, while cherries or plums are renewal pruned in a fan or informal design.

Getting Started

Once you have decided on the site, and selected the tree, you will need to establish a frame to work from. Heavy wire (12 or 15 gauge) should be strung from eyebolts on the wall or fence to provide a frame. Three levels of wire are usually sufficient for starting an espalier design. The bottom wire should be at least half a meter from the ground with the remaining wire spaced from one half to one meters apart. A free-standing trellis can also be built by sinking sturdy posts into the ground and running wires between them. The trellis must be strong enough to support what will eventually be a heavy weight of branches and fruit.

Apples are best espaliered starting with a whip; however, most nurseries supply trees that are larger than this. Your best bet is to find a young tree with evenly spaced branches. Even if the branching is not on a plane, young branches can be slowly trained into almost any direction. Plant the tree six to eight inches from its support, ensuring that the graft union is at least two inches above ground level.

Branches chosen to be part of the design can be tied with string or bits of rag to bamboo canes; this keeps them absolutely straight. The canes can then be slowly lowered (over a few weeks) to the wire. Branches which are not part of the design can be pruned off in the spring. Also rub off any flower buds; this permits the tree to direct its energy into vegetative growth until the espalier pattern is complete. If you are bending a branch and it should happen to crack, don't despair. A partially broken branch that is securely fastened to the frame, will usually heal to the point of appearing normal.

When starting a T-design with a whip in early spring, snip the stem at the height of the first wire Ø leaving at least three buds below the cut. These buds will develop into shoots during the first growing season. Tie these to bamboo canes and lower two branches to the wire, leaving one branch vertical. The next spring, prune this vertical branch to the height of the next wire, where new shoots will form to repeat the pattern. Each year a new layer is formed; therefore, on a three-layered trellis, at least three years are required to form the pattern. During this time no fruit should be allowed to develop. You can reduce the establishment time by a year or more if you search your local nursery for a tree that already has the branches properly spaced for the first couple of tiers. If one side branch is growing more vigorously than the opposite branch, lower the strong branch slightly and raise the weak branch until they are more closely matched. In the spring, prune all lateral branches back to three buds. The basal buds will become fruiting spurs.

Less-rigid fan espaliers are ideal for cherries and plums which bear fruit on the previous year's wood. Therefore, a new set of branches are trained into position each year parallel to last year's branches. Each spring, the branches that had fruit last summer are removed. All branches emerge from just above ground level.

While it may take time to complete the work, a mature espalier is certain to catch the eye of almost every visitor to your garden.

Celine Burns is with the Horticulture Information Service, Department of Horticulture Science.

Pesticides

Celine Burns

The word "pesticide" is an umbrella term for all insecticides, herbicides, fungicides, rodenticides, wood preservatives and household disinfectants that may be used to kill some living thing. All garden chemicals sold as pesticides must be registered by Agriculture Canada in Ottawa. Each pesticide is registered for a specific use on a specific plant, and must only be used in accordance with its registration. Only those products labelled "domestic" may legally be sold for use in the home by unlicensed homeowners. This category is designed to help prevent highly toxic and potentially dangerous chemicals from being used by inexperienced people in and around the home. Although the products we use in our homes are registered for domestic use, all proper safety precautions must be used with these products.

On all containers of pesticides which represent a threat of poisoning to people will bear the internationally recognized symbol for poison, the skull and crossbones. Three distinct degrees of toxicity for various products will be indicated by the border surrounding the skull and crossbones. The least toxic poisons are indicated by a "caution-poison" symbol which is a triangle (like the shape of a highway yield sign) around the skull. A diamond border (like the shape of a highway warning sign) indicates a "warning-poison" label that is more toxic than the first, and a hexagon border (like a stop sign) indicates a dangerous poison level. An easy way to remember this is that the more sides the border has (3,4 or 6) the more dangerous the product is to your health.

A "caution-poison" (triangle) label indicates the lowest level of hazard. While using these products, impenetrable gloves and skin protection are required. A "warning-poison" (diamond) label indicates a moderate hazard to the user. Goggles, gloves and skin protection are required. The "danger-poison" (hexagon) symbol indicates high hazard and requires the user to wear goggles, respirator, gloves and skin protection. The Danger-Poison symbol must be used for all liquid pesticides which contain more than 10% petroleum distillates, regardless of the toxicity of the active ingredient. Therefore, not only does toxicity depend on the active ingredient and its concentration, but also on the diluents.

In a few cases, pesticides may be considered non-toxic to humans. Roundup is one such chemical. For these products, Agriculture Canada does not require a poison indication symbol on their containers. In all cases, no matter what the level of toxicity, users should avoid fumes and spray mist, and use the products with care.

The first and most basic question to ask in the safe use of any pesticide is whether or not the particular application in question is needed. By far the safest means of using pesticides is by not using them at all. Very frequently the pesticides used in home and garden situations are applied after the damage is done, and do not contribute significantly to correcting the problem. If you should decided that the use of pesticides is warranted for your particular case, the second basic rule is to always read the entire label fully before starting. Failure to read the directions is one of the main reasons that pesticide treatments are ineffective, and also a main cause of accidental poisoning, or damage to non-target organisms.

Pesticides should be stored in their original containers in a dark, cool locked place, out of the reach of children and pets. It is illegal to store a pesticide in any container other than the one it was sold in. Pesticides should only be applied when and where they are actually needed. If everything is going well in the garden, a blanket fogging of insecticide "just in case" is more likely to create a problem than prevent one. All gardens normally suffer from some degree of pest damage; poor plant health and poor growing conditions have a lot to do with the extent of the damage. Pesticide use is often an individual decision based on a question of tolerance to the insect, weed, or disease. Living with a few blemishes or rolled leaves may not be worth the cost of control (money + time). Homeowners should educate themselves on each infestation in order to make an informed decision about whether chemicals are necessary.

An application of insecticide when needed may actually lead to increased insect damage because the insecticide will also kill predatory insects which feed on the insects you are attempting to control. Without the predators present, populations of the insects causing damage may increase rapidly. Spot treatments are recommended rather than blanket applications. Just because you are mixing up a pesticide to treat one plant, does not mean you should mix up ten times as much and treat the entire garden. The Bees Act makes it an offense to spray insecticides on fruit and vegetable crops while they are in bloom. In fact, any pesticide spraying is best carried out at dawn or dusk when all bees will be in the hive, and unlikely to be hit by the spray.

The rate of application is critical. All pesticides should be measured carefully. Use a cheap set of measuring spoons purchased for use with pesticides only. These should be marked with indelible ink "for pesticide only," and stored in the same locked container where you store your pesticides. Increasing the concentration above that which is recommended can actually decrease the effectiveness of the product, so resist the temptation. When herbicides such as 2,4-D are applied at too high a level, leaves may burn before the plant has a chance to absorb the chemical and move it to the roots, resulting in a poor kill.

Insecticides applied at higher than indicated rates may cause leaf burn. Use separate sprayers for herbicides and insecticides. Residues left from the 2,4-D you used to kill your dandelions in spring may kill your rose bush when you are attempting to kill an insect pest later in the season.

Pesticides may be contact or systemic, specific or non-specific. A contact herbicide is not absorbed into and transported through the sap of the plant. Top-killers such as Top Gun must be repeatedly applied as they will kill only the part of the plant that they contact, and will not kill the root. Roundup is a systemic, non-specific herbicide. It will kill all parts of a plant if it is applied to green leafy growth. It does not remain active in the soil, however, so it is safe to plant into Roundup- treated areas. Insecticides may also be systemic. A systemic insecticide such as Sevin is absorbed into the plant so that feeding insects are killed from the insecticide contained within the plant's sap. The use of systemic insecticides can counteract uneven spraying and wash-off by rain. Sevin is also a contact insecticide, meaning that any insects that are actually hit with spray will die.

Pollination

By Celine Burns

Spring may have arrived late this year, but the fragrance of blossoms is finally beginning to fill the air. From our somewhat selfish perspective it is easy to believe that the fragrance and beauty of flowers exist entirely for our benefit. However, the primary goal of a flower's attractiveness is not to inspire our appreciation, but to seduce insects into visiting and pollinating it. If it were not for the activities of bees, our efforts to grow things like apples and plums would be fruitless.

Any activity which results in the transfer of pollen grains from the stamen to the stigma of a flower can be thought of as pollination. If the pollination results in successful fertilization, the undeveloped seeds in the ovary of that flower will begin to develop into viable seeds. With their development, the structures surrounding them will also begin to develop Ø forming what we know as a fruit. In all but a few cases, fruit development will not take place unless seeds are developing within. If you've ever cut open a lopsided apple, you may have noticed that there were a greater number of mature seeds on the larger side of the apple. These seeds were fertilized following pollination and triggered the fruit tissue around them to develop.

Of course, insects cannot take all the credit for pollination. Many plants have flowers which rely mainly upon wind for pollination. Grasses, evergreens and many of our most common deciduous trees rely upon the wind. In general, the less noticeable the flowers on a particular plant are, the more likely it is that the plant is pollinated by wind. When's the last time you noticed your maple trees flowering? In fact, most of the maples in the province flowered about a week ago, but you may not have noticed because the flowers are small, drab and non- fragrant. Since Saskatchewan's wind can find them whether they are conspicuous or not, wind-pollinated flowers do not devote a great deal of energy to making themselves attractive.

The array of flower sizes, shapes and colours can be staggering. However, the complexity of flowers doesn't stop there. A particular flower can be either male, female or both, depending on the types of floral organs present. A flower which is both male and female has stamens (male) and pistils (female). If a flower has only stamens without a pistil, it is male, and if it has only a pistil without stamens it is female.

As if this were not complex enough, the particular associations of a flower can be different. Some plants have separate male and female flowers on the same plant, while other plants will have only male or only female flowers. The technical term for a plant that has both male and female flowers on the same plant is monoecious (mon-ee-shus) while the term for a plant that has either all male, or all female flowers is dioecious (di-ee-shus).

Monoecious and dioecious plants can be problem-solvers or problem-causers. For example, corn is a monoecious plant. The tassels at the top of the plant are the male flowers, while the female flowers are found below in tight clusters we call cobs. Each kernel of corn has one piece of silk attached, and this is where the pollen from the male flower must land if that particular kernel is to develop. Corn is a wind-pollinated crop (like most grasses); therefore, problems can arise when corn is planted in one single long row. Pollen falling from the male flowers on the top of the plant is most likely to land on a piece of silk if the corn plants are grown in several adjacent short rows, rather than one long single row. If your cob of corn has many empty spaces where kernels did not develop, you can be certain there was a pollination problem. Also note, that the kernels toward the tip of the cob are often undeveloped. This is because they were too young to be pollinated.

Asparagus is a dioecious plant, so one plant will be entirely male and another will be entirely female. Growers have found that if only male plants are grown, yields increase by about 15%. This is because these plants do not divert energy into the production of seed pods later in the summer, so they can store more energy in the root for next spring's crop.

One sure way of being "un-poplar" in your neighbourhood is by growing a large female poplar tree. Poplars are one of the most obvious examples of dioecious trees, and anyone who has ever seen a female poplar in June knows why the name "cottonwood" has long been associated with these trees. Near some female trees, there can be a near blizzard of white fluff deposited in June. Since only female trees produce the fluff, however, it is an easy problem to avoid, by growing only male trees. Most commercially propagated poplars are male clones, grown as cuttings from male trees. One notable exception is `Walker' poplar, a female clone that should only be used if fluff is not a potential problem.

The complexities of flowers and pollination have evolved together in terms of flower structures and functions. Many flowers are able to self-pollinate and or accept pollen from other flowers (cross-pollinate). A number of plants that naturally self- pollinate have developed specialized methods or structures which prevent cross-pollination. A violet has already pollinated itself before it has opened, so it is almost always pollinated by its own pollen. The stigma of a tomato flower grows through a sheath of anthers, resulting in almost certain self-pollination.

Another group of plants can never be pollinated by their own pollen. Apples, crabapples, many plums, blueberries, hazelnuts and some grapes are self-incompatible. This means that they require the pollen of a genetically different, but closely related plant before fertilization of the seeds can occur. Flowering crabapples, for example, may be used in apple orchards where a single type of apple is being grown. Their long and profuse bloom period, combined with a heavy production of pollen permits them to act as excellent pollinizers for other apple trees. When buying an apple tree for your yard it is most often recommended that you have two different cultivars of apple. This is so each apple will be available to pollinate the other. In the city this is a less critical consideration, because your neighbours' apples will often serve as pollinizers. In rural areas, however, where the nearest apple or crabapple tree may be more than a kilometre away, two trees should be grown in close proximity so assure that each will pollinate the other.

© 1995 Celine Burns

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Sustainable horticultural information, offered free of charge to the public with the support of the University of Saskatchewan Extension Division, the Department of Plant Sciences and the Provincial Government.