Often times site conditions are such that it’s best to work with the existing landscape rather than make extensive changes. These types of sites often become very successful gardens. A shady spot beneath a stand of trees, for example, is the ideal location for a woodland garden. Instead of trying to impose a garden through extensive pruning and soil conditioning, prepare the site for woodland plants, such ferns, shade loving shrubs and perennials. Plants suited to these conditions will grow and thrive without major site preparation.
Limited site manipulation if fine, lower branches may need to be pruned to allow access into the garden, smaller trees may should to be removed to avoid competition and some organic compost can be added to the site in order to create optimal growing conditions.
Woodland gardens, which mimic the forest landscape, have four vertical elements; the canopy layer, the understory, the shrub layer and the ground layer.
Begin your planning with choosing the appropriate canopy layer for your garden. In Urban area this usually means a smaller tree which provide a light dappled shade. Thornless honeylocust tree and birch are generally suitable for city conditions as they provide light shade, grow tall and narrow and have interesting winter form. Don't make the mistake of planting too many trees or inappropriate larger trees which out grow the space provided. Smaller tree can be placed about 8' from one another, so if you have the space plant more than one tree. Larger shrubs can be used in place of trees if the space requires smaller plantings. Viburnum and Spicebush, when limbed up can provide shave for lower growing perennials and groundcovers. Remember to include in your plan a few variegated plants; they will brighten up a shade garden and add color through the summer months.
Multi stemmed tree can give the effect of many trees.
Urban areas generally have poorer soil than gardens in the suburbs or country so some preparation may be necessary before you plant.
Soil composition is also critical to the growth of healthy root systems. Most plants will not do well in exceedingly sandy soil or in poorly drained clay soil. Grading and conditioning the site to provide adequate drainage should be done before you begin planting. If you’re planning a garden in clay soil composted bark or other course textured organic material will improve drainage. It may also be necessary to build up the garden with an earthen berm. This will allow oxygen to reach the roots and cause excess water to drain away from the plant rather than collecting beneath it.
Because they are so well drained, sandy soils don’t hold water or nutrients well. Sandy soils, as opposed to clay soils, require the addition of water retentive organic matter such as manure, compost and peat moss. When adding your soil amendments avoid uncomposted bark or wood chips as they tend to rob plants of nitrogen.
Compacted and poorly drained soils contain little oxygen, which plant roots need in order to survive and grow. Though some plants tolerate soils with low oxygen, most grow poorly or die. Although any type of soil can become compacted, clay offers plants the most difficult challenge.
One issue gardener's need to be aware of is the fact that younger trees are small and often don't provide the shade needed by the woodland plant in your plan. If, when you plant your new tree, the shade is not adequate plant wait until the tree cast enough shade for your plants to survive. In the meantime use part sun plants and transplant them to another spot in the garden when they begin to get shaded out.
Use a rich diversity of plants in your woodland garden. Gardens plants with a mix of bulbs, ferns, shrubs and perennial will provide interest though every season and more closely resemble the native woodland landscape. In the beginning avoid planting too many plants since as the grow they plants will become crowded and will need transplanting.
Also don't overlook plants with winter interest.