Deciduous Trees

Learn to Identify and Grow Deciduous Trees

A course for:  Nurserymen, landscapers, arborists, foresters and horticulturists

Deciduous Trees are widely planted, particularly in temperate and colder areas of the world. They are very important for both amenity horticulture and forestry. This course is a great foundation study for new or experienced horticulturists, landscapers, arborists, nursery workers, gardeners, parks managers; or anyone else concerned with the selection, propagation, care, maintenance or harvesting of deciduous trees

Lesson Structure

There are 8 lessons in this course:

1. Introduction
   • Taxonomy
   • Planting
   • Plant Selection
   • Soils
   • Nutrition and Fertilisers
   • Pruning
   • Propagation
2. Maple (Acer)
   • Introduction
   • Propagation
   • Culture
   • Pest and Disease
   • Species and Cultivars
   • Growing Acers in Pots
   • What affects foliage Colour Changes
3. Birch (Betula)
   • Characteristics of the Betulaceae Family
   • Betula genus overview
   • Commonly Cultivated Betula species and cultivars
   • Betula species not commonly grown
   • Birch Propagation; cuttings, layering, seed, grafting
4. Ash (Fraxinus)
   • Introduction
   • Fraxinus sub groups; sub genus Ornus, sub genus Fraxinaster
   • Variations in leaf colour
   • Selected cultivars
   • Less commonly cultivated species
   • Culture; pests, disease, propagation, etc
5. Oak (Quercus)
   • Overview of genus Quercus
   • Species and Cultivars
   • Culture
6. Prunus
   • Overview of the genus Prunus
   • Culture
   • Cultivars and Species
   • Plums
   • Apricot
   • Prunus persicae (Peach and Nectarine)
   • Cherry
   • Prunus Propagation
7. Other Deciduous Trees
   • Alnus
   • Cedrella
   • Lagerstroemia
   • Liriodendron
   • Liquidambar
   • Magnolia
   • Malus
   • Platanus
   • Populus
   • Pyrus (Pear)
   • Salix
   • Sambacus
   • Syringia
   • Ulmus (Elm)
8. Special Project

Aims

• Review foundation knowledge in plant identification and culture as needed to properly build expertise specific to deciduous trees
• Develop knowledge in classification, identification and culture of plants, from the genus Acer.
• Develop knowledge in classification, identification and culture of plants, from the genus Betula
• Develop knowledge in classification, identification and culture of plants, from the genus Fraxinus.
• Develop knowledge in classification, identification and culture of plants, from the genus Quercus.
• Develop knowledge in classification, identification and culture of plants, from the genus Prunus.
• Review a range of other significant deciduous tree genera not covered previously in this course.
• Plan the establishment of a collection of different cultivars of deciduous trees suited to growing in a specified locality.

WHAT MAKES FOLIAGE CHANGE COLOUR IN AUTUMN?

Deciduous plants shed their leaves in autumn or early winter, and are fully or partially devoid of foliage over the colder months of the year. This is an adaptation that allows the plant to better survive unfavourable conditions (such as extreme cold).

• Prior to leaves dropping they undergo a period of senescence.
• Senescence is the period during which leaf cells progressively die.

Over the senescence period, tissue at the leaf base progressively dies, until finally a complete section of tissue between the leaf and the stem is dead (At this point there is nothing left to hold the leaf to the stem; so it detaches and drops to the ground).

As senescence occurs, the amount of chlorophyll in the leaf (which gives it the normal green colour) reduces. Chlorophyll is actually only one of many pigments that generally occur in leaves; but it is usually the strongest pigment, and for that reason alone, most leaves usually appear green if the plant is healthy.

Other types of pigment chemicals commonly found in leaves include:

• Anthocyanins –Reds, Blues and Purples
• Carotenoids –Yellows and Oranges

Generally Carotenoids also decompose rapidly in Autumn, but Anthocyanins break down much more slowly.

Often Anthocyanins can still be at close to 100% normal levels when only 40% of normal chlorophyll and carotenoids remain.

Anthocyanins are produced through chemical processes, from excess sugars in the leaves, particularly in the presence of bright light. In view of this fact; the level of anthocyanins will be stronger if the plant has been actively photosynthesising (producing sugars) over summer, combined with lots of bright autumn days (if weather is frequently overcast and dull in late summer and autumn; the production of anthocyanins is decreased).

Lower temperatures in autumn reduce the movement of sugar around the leaf, so if the weather changes from warm to cool fast, the leaf sugar remains high and anthocyanins build up; otherwise the levels of these pigments might not be so high.

High levels of anthocyanins will generally result in more vivid autumn foliage colours

Tips for Growing Deciduous Trees

Maples (Acer)

• There are approximately 200 species in this genus
• Acers are hardy in cool and temperate climates. Some species tolerate warmer climates, but they are best grown in cooler areas. Some species will tolerate extreme cold and dryness, but few, if any, tolerate hot humid climates.
• They prefer a position in full sun to semi-shade.
• Most maples need cool, moist, well-drained soils for best results. Many maples prefer soil with a higher pH, so the addition of lime to acidic soils is beneficial.
• They have a spreading, often shallow, root system and small species are unlikely to cause any major problems in terms of root damage.
• Protect from hot and strong winds.
• Mulch and feed annually. Well rotted organic fertilisers or manures can be applied in early spring.
• Irrigate during dry periods, particularly during drought times.
• Light pruning might be undertaken to shape a plant or remove dead wood; however, regular pruning is generally not needed, and may detract the from the natural shape of the plant.
• Pests are rarely serious but may include mites, thrip and borers.

 
Ash (Fraxinus)

• Approximately 60 species, deciduous trees.
• Lifespan may be up to 300 years.
• Generally spreading crown, sometimes upright. Many dwarf, and weeping cultivars available.
• Avoid high pH or sandy soils.
• Grow in full sun or partial shade.
• Pruning is generally not necessary.
• For best results, ash trees must have well drained soils, but prefer some moisture – never fully dry, never very wet. Some will tolerate very dry soils though, particularly once well established.
• Prefers ample organic matter – if soil is hard clay or sandy, mulch thickly.
• Generally very hardy once established.
• Winter buds of most are felt like to the touch.

Birch (Betula)

• Approximately 60 species.
• Shallow, fibrous roots   not as damaging as many other large trees.
• Tolerates extremes of wind, cold and snow.
• Most are relatively short lived (they do not live for hundreds of years like Ash or Oak).
• Extended periods of heat and dryness will cause leaf margins to burn, will slow growth, and may cause death.
• Main problems are wood rot and leaf rust. Avoid making large cuts into live wood, remove dead wood early spring each year. If growing rapidly they will heal over cuts, but if growth is slow, cuts can become infected and cause rot. Fast growing young plants are best pruned to one leader, to encourage a single trunk. (This makes a stronger framework that is less likely to develop splits in branches as a mature specimen.)
• Surface roots are relatively aggressive, making it difficult to grow all but very hardy plants below a birch.
• Will grow in most soil types, but prefers freely draining moist and acidic soil.
• Will grow in sheltered or exposed positions, many tolerate coastal conditions or do well in mountains, but most are not good in arid areas.
• Most tolerate temperatures to minus 15 degrees Celsius; some lower.

Oak (Quercus)

• Approximately 450 species.
• Prefer cool mountain areas, and moist well-drained, fertile soils.
• Avoid wet or sandy soils. Most don’t like shallow soils.
• They have a deep taproot and strong root system which can be damaging.
• They grow best in full sun to filtered sunlight.
• Most have leaves with a wavy or indented edge.
• Canopy is often broad, and usually dome shaped.
• All are long lived.
• Most are hardy to at least minus 10 degrees Celsius.
• Foliage allows filtered sunlight through.
• Almost all species are large trees.
• Autumn foliage colour can be reds through yellows to brownish tones.
   

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