Of course, it is best to choose plants that are suited to the different sites in your yard. You can improve growing conditions, though, by improving the soil and pruning trees.
Most shade plants prefer slightly acidic soil with lots of organic matter. It is a good idea to improve your soil by working in 5 to 10 cm of compost.
Whenever you add new soil, use a mixture of equal parts garden loam, potting soil and peat moss.
You can also build raised beds to solve drainage problems. In extreme cases, you may wish to add an underground drainage system.
Finally, you can decrease the amount of shade by carefully pruning a tree. Sometimes merely removing a few low-growing branches will allow more light through. If this is not enough, you may wish to thin the crown of the tree. It is best to proceed as follows:
- remove any dead, diseased or dangerous branches;
- remove any branches growing vertically or in an odd direction that will spoil the tree's appearance;
- trim any primary or secondary branches that are growing too close together;
- never remove more than 20% of a tree's branches at any one time.
Under a tree
Establishing a flower bed under a tree require some precautions. In order to protect the roots, avoid working the soil too deep near the trunk and under the branches. Adding a slight layer of soil (less than 15 cm) will cause no harm if one takes care not to cover the base of the trunk. Choose species with a shallow root system, preferably young plants that will adapt faster than mature ones. If the soil is compact and acidic, plant mosses or spead a decorative mulch.
Most shade plants prefer moist soil. Mulching is a good way to maintain lots of organic material in the soil.
Adding 4 to 6 cm of compost in spring will help to retain moisture, keep down weeds and increase the proportion of organic matter in the soil.
For native plants, it is enough to add compost once a year, because overly fertile soil will adversely affect their natural growth.
More demanding plants will benefit from a springtime application of fertilizer that will nourish them for 2 or 3 months.