HOW TO GROW BIRCH
Birch belongs to the plant family Betulaceae. The genus Alnus (Alder) also belongs to the same family.
Some authorities have occasionally included the genus Corylus in the Betulaceae, though others place it in a separate family: Corylaceae.
Characteristics of the Betulaceae family:
- Monoecious trees & shrubs
- Leaves are undivided (ie. not palmate or pinnate), but with a toothed (serrated) margin
- Leaves arranged alternate along stems
- Flowers occur typically in 3 flowered cymules, and form into terminal catkins
- Flower bracts can often grow into a scale like organ that frequently remains attached to the fruit through to maturity of the seed (ie. a wing that helps seed dispersal).
- Fruits are a 1 seeded nut, not containing an endosperm.
- Most have attractive autumn foliage.
- Birch will grow in most soil types, but prefers freely draining moist and acidic soil.
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° C; some lower.
Betula all come from the northern hemisphere; from temperate and arctic regions.
(Alnus come from northern temperate regions south as far as Assam and South east Asia; and also from the Andes in South America).
In their indigenous habitats, both birch and alders are used for their wood, and is some situations for their bark and leaves; as a source of oil, dyes and even as a food. More widely, both genera are important as ornamental plants. Some species wood is used as laminates in fine curved furniture.
B. lenta is the main source for Oil of Wintergreen.
General Characteristics of Most Betula species
- Approximately 60 species.
- Grow on poorer drained soils, but soil must remain moist.
- Shallow, fibrous roots not as damaging as 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 depending on your location and country. In some regions and countries there are a range of different problems for birch including borers, leaf blisters, leaf rust, leaf mosaic virus and also problems with pests such as Aphid galls, leaf miner, and stem galls. Check with local Botanical authorities and nurseries in your region for information that may impact on the growth of these plants in your local area as there are regions where these plants are relatively pest and disease free.
- 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.
How Betula are Propagated
Most birch are grown by seed and grafting/budding, however some are grown successfully (even commercially) by cuttings. Seed is generally undesirable, except to produce rootstocks, because of the uncertainty and variation in appearance of plants grown from seed. Grafting onto seedling rootstocks produces reliable results and quality plants, but it is a more expensive process than cuttings. For this reason alone, cutting propagation has been used commercially in some places.
Semi-hardwood leafy cuttings or softwood cuttings, are the methods mostly used.
Softwood cuttings are more commonly reported as the preferred type.
Species grown successfully from cuttings include B. alleghanensis, B. lenta, B. nigra, B. papyrifera and B. pendula. In Central Europe, B. mandschurica has grown well by hardwood cuttings taken in winter and placed over 18 degrees C. B. pendula generally strikes easily from softwood cuttings, with some exceptions – the occasional cultivar may be difficult. B. pubescens is significantly easier to strike than B. pendula.
Cuttings are normally taken around 7-10cm long, although some growers have had success with longer cuttings. Dip the cuttings in a disinfectant for sanitation. Treat with hormone (8000ppm IBA Talc for most species; B. papyrifera has been grown well with as low as 4000ppm IBA for a quick dip or 2500ppm for 10 secs). 1500 ppm IBA dissolved in propylene glycol and used as a quick dip has given good results in trials. Use a well draining propagation mix such as 1 part perlite: 1 part peat.
Place the cuttings under mist during most daylight hours (do not mist at night). Bottom heat is not necessary. Roots can form in 3 weeks under ideal conditions. Keep the cuttings in a greenhouse over winter then plant into pots or open ground in spring. In very cold areas, provide minimal heating over the first winter. Avoid cuttings dehydrating while handling.
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