Build your knowledge about Deciduous Trees.
This course is a journey of exploration that will help you to develop your understanding and awareness of deciduous trees, how to propagate and grow them and how they can be used in the landscape. Students will look at including Acer / Maple, Birch, Ash, Oak, Prunus, and many more varieties.
COURSE STRUCTURE AND CONTENT
There are eleven lessons in this module as follows:
- Plant classification
- Scope and nature of Deciduous Trees
- Planting methods
- Using trees ... creating a mood with trees
- Soils, nutrition, pruning
2. Maple - Acer
- Scope and nature (approx. 200 species plus cultivars)
- Cultural needs
- Selected species and varieties
- Propagating maples
- Grafting, Seed, Cuttings
- What makes foliage change colour
3. Birch - Betula
- Birch family characteristics
- Birch cultural requirements
- Species and cultivars
- Propagating Betula ... cuttings, layering
- Grafting, Budding techniques
4. Ash - Fraxinus
- Overview of Fraxinus
- Sub genera (ornus and fraxinaster)
- Cultural requirements
- Understanding autumn colour variations
- Selected popular species and cultivars
- Less commonly grown species
- Culture of Fraxinus; pest, disease, propagation, etc
5. Oak - Quercus
- Overview and cultural requirements
- Scope and nature of the genus
- Selected species and cultivars
- Peach and Nectarine
- Prunus propagation
7. Other Deciduous Trees
8. Special Project
A problem based learning project with the following aims:
- Identify factors that will affect the successful culture of a specified group of deciduous trees in a specified locality.
- Determine criteria for selecting cultivars of deciduous trees.
- Select cultivars of deciduous trees appropriate for cultivation in a specified situation.
- Choose plant establishment techniques appropriate to the cultivation of selected deciduous tree cultivars in a specified locality.
- Determine a routine 12 month maintenance program for a selected collection of deciduous tree cultivars to be grown in a specified locality.
- 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 this 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 Anthrocyanins break down much more slowly.
Often Anthrocyanins can still be at close to 100% normal levels when only 40% of normal chlorophyll and carotenoids remain.
Anthrocyanins 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 anthrocyanins 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 anthrocyanins 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 anthrocyanins build up; otherwise the levels of these pigments might not be so high.
High levels of anthrocyanins will generally result in more vivid autumn foliage colours.
How Much Don't You Know About Oak Trees?
In many parts acorns are considered as food for animals and not humans; , but some native peoples have used acorns as a significant food source. Native Americans gathered and stored acorns. The nuts were then ground to a meal and used for making pastry and bread.
Oaks are wespread in northern hemisphere; with around 600 species. They are both deciduous and evergreen trees, and sometimes shrubs. Some species can live 1000 to 1500 years. Many deciduous species have attractive autumn foliage, leaves are variable amongst species, male flowers are yellow catkins borne in spring, female catkins are inconspicuous, rounded acorn nuts are held in cup-shaped husks
Oaks prefer a deep and moist but well-drained soil, open position in full sun, tolerate part shade, mulch young trees with well-rotted manure in spring. Prune for shape.
Named cultivars are commonly grafted on seedlings; seed needs stratification (period in cold) to induce germination and must be planted within two months.
There are both hardy and half-hardy species. They can be attacked by caterpillars and chafer grubs may attack leaves, gall wasps may cause galls on leaves, stems, roots and buds. They are known diseases include a range of fungi which can cause dieback and canker, bracket fungi may grow on trunks and branches, powdery mildew may affect leaves and stems, and honey fungus can kill trees.
Uses: Shade tree, feature tree, autumn foliage, windbreak, screen, hedge, large garden tree, food source for animals and occasional food source for humans.
Bitter tasting chemicals in the nuts should normally be removed. Do this by spreading acorns1-2cm thick over a porous cloth and washing hot water through. Repeat the wash at least twice until bitterness is removed. Nuts can then be dried in an oven and ground into a meal for use in baking.
Q. alba (White Oak, American White Oak): 15 to 20m tall (occasionally 30m); from Canada and the USA mainly occurring on alluvial soils near rivers. Leaves have a heavily lobed margin, pale grey bark on main trunk and branches. Many hybrids are known, between this and other species. Autumn foliage can become deep claret-red. Trees tend to bare good seed yields only once every 4 to 10 years. Seed germinates quickly if planted fresh. Seed germination rates can vary from 50 to 99%. Eaten by Native Americans, roasted, raw or in bread.
Q. bicolor (Swamp White Oak): 15 to 25m tall and up to 10m diameter, leaves are shiny dark green above autumn foliage yellow to brownish. Good seed crops every 3-5 years. Seeds planted fresh or after 1-3months stratification should give over 90% strike rate Eaten by Native Americans, roasted, raw or in bread.
Q. lobata (Valley Oak): From Californian valleys, to 30m tall, drooping branches, heavily lobed leaves, dark green leaves with a yellowish mid rib, fine hairs on under surface but smooth and shiny upper leaf surface, foliage turns yellow-brown in autumn. Were eaten by native Americans in California.
Q. macrocarpa (Mossy Cup Oak, Burr Oak): 25 to 35m tall and to 15m diameter, very rough, ridged grey-brown bark; lobed glossy green foliage turns yellow brown and falls early in autumn. Good seed crops occur every 2 to 3 years. Germination rates are reported at around 45%. Most nurserymen sow seed as soon as collected, though one study reported increased % strike after cold stratification. Eaten by Native Americans, roasted, raw or in bread.
Q. robur (English Oak, Common Oak): 15 to 25m, needs shelter from hot dry winds, does best in cool areas. Deeply furrowed grey bark, foliage is bright green in spring but becomes a glossy darker green as the season progresses. The under surface of the leaf is paler. Leaves are lobed, but not as heavily as many oaks. Autumn foliage is yellow-brown. Several named cultivars are grown (usually propagated by grafting). Good seed crops only occur every 2-4 years. Seed sown immediately after collection and cleaning (removing caps) can be expected to give a 70% germination rate. It is recommended to soak seed for an hour or two in water before sowing. Has been used as a food by humans in Europe during famine; though the bread made from acorns is reportedly not very palateable.
Q. virginiana (syn. Q. virens; Live Oak): Evergreen tree to 20m tall from south eastern USA, dense foliage, broad dome shaped crown. Though normally grown by seed, this is one of the few oaks reported to have also been grown successfully by cuttings.Eaten by Native Americans, roasted, raw or in bread.
Other species that are eaten by humans are:
• In Japan Q. glauca, Q. prinus and Q. emori
• In Europe Q. ilex var. Ballota and Q. aegilops
• In America Q. prinus, Q. lobata and Q. emori
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