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Jane's Garden 8/17/14: Maintain a shade tree

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Many homeowners like to plant shade trees as specimens in lawns, to frame a home and to shade buildings. New trees are usually small plants in easy-to-handle pots. Careful consideration should be given to the mature size of the tree species, its brittleness, wind resistance and if it is evergreen or deciduous in winter.

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A clump of River Birch, Betula nigra, with three to five trunks eventually reaches 40 to 80 feet tall with a 20 to 40 foot spread. If planted to shade a building, it should be 6 to 10 feet away. Rain runoff from the roof will provide extra water, so River Birch can grow more than 25 feet tall in just four years. Branches will have to be eliminated on the building side until 10 feet above the roof eaves. As this species sheds its leaves for winter, the weaker winter sun can warm the building. In summer, River Birch can provide dense shade over walls and roofs.

Trees planted as lawn specimens should have at least 3 feet of grass-free ground surrounding the trunk. This tree ring prevents damage from lawn mowers and eliminates the need for a weed whacker. Shed leaves can be blown or raked onto the tree ring as decorative top mulch. Hand gathered pine needles are excellent to deter weed seeds from sprouting.

For the first few years of a sapling’s life, always prune off lower branches while they are small so the tree will grow taller faster. The resulting canopy will be higher. Prune at the thickened branch collar and leave no stubs. The tree will heal over quickly from the undamaged collar. Prune annually until the first branch is at least 10 feet high. Branches need to be kept above foot and vehicle traffic. Keep in mind that branches sag with age.

As trees mature and provide a wide shady canopy, grass below will die due to lack of sunlight. Weeds may invade the surrounding ring. These can be pulled while young or killed with a 3 percent to 5 percent glyphosate solution, a non-restricted herbicide.

An alternate solution is to install shade-tolerant plants. Study the base of the tree trunk to see where thick roots are radiating. Try probing with a spike to find spaces between the large anchoring roots where small potted plants could be planted.

Choose three to five shrubs that will mature to about 3 to 5 feet diameter. Shrubs planted 3 feet from the trunk should have enough space and light to thrive. Be aware the established tree roots will be absorbing the rain water and nutrients. You may need to irrigate understory plants and supply time-released fertilizer annually.

Azaleas can flower in shady tree rings. Study the internet then choose Encore azaleas with the fixed mature height and diameter you want. After selecting the appropriate height, then decide on a color. Patented Encores are worth the extra money, as they repeat-bloom from September to March rather than the three to four weeks of older varieties.

Beneath a River Birch planted to shade the west wall and roof of my garage, I planted an ‘Autumn Cheer’ and three ‘Autumn Angle’ Encore Azaleas. Both will mature only 3 feet high and about 3 feet diameter. The little azaleas are 3.5 feet apart. In the spaces between are ‘Queen Mum’ agapanthus bulbs which will also flower in shade, but not until June or July. Florida violets and native rain lilies are filling in as a self-seeding ground cover.

Coonties, Zamia pumila, a native cycad, grow well in tree rings. Coonties tolerate full sun in winter and dense shade in summer beneath shade trees. Volunteer Friends of Dunnellon Public Library recently planted 40 mature male coonties in 12 tree rings scattered around the parking lot. After the first month, Coonties need only a quart of water weekly as they become established.

Jane Weber is a professional gardener and consultant. Semi-retired, she grows thousands of native plants. Visitors are welcome to her Dunnellon, Marion County, garden. For an appointment, call 352-249-6899 or contact JWeber12385@gmail.com.