Woody plants need water less frequently than other ornamental plants because of their deep or wide-spreading roots. When woody plants do need water, however, they require greater quantities of it at once. To water them efficiently, set the sprinkler or irrigation system at a relatively low pressure but leave it on for a longer period of time. As a result, the tree or shrub receives roughly the same amount of water as other plants, but slowly, soaking the root zone to a greater depth. Superficial waterings, such as those for lawns, do more harm than good to woody plants.
Exposure of woody plants to cold winter winds can cause problems due to desiccation, even among plants that are fully hardy. The damage is most evident in conifers and broad-leaf evergreens, which can turn brown by spring, especially on the side most exposed to winter winds. Damage to deciduous plants may be obvious only when they green up in spring. Leaf or flower bud damage can be seen by the dieback in different areas.
Exposure to cold can cause desiccation.
Woody plants of marginal hardiness or those grown beyond their normal hardiness zone will require special winter protection. Surround them with burlap or snow fencing (or a combination of both) to filter winds and help collect snow. Fill enclosures with straw or oak leaves packed around the stems. You can also use the branches of conifers to cover them, especially on sides exposed to dominant winds. Vines can be taken down from their trellis, tied together, laid on the ground, and covered with a thick mulch of leaves.
Trees and shrubs that bloom in spring are highly appreciated because they bring color to the garden so early in the season However, this also leaves their buds particularly susceptible to damage from late frosts. As long as the flower buds are dominant, little danger of damage exists. If frost threatens when the buds have begun to swell or open, turn on the sprinkler and set it so the plant is soaked from top to bottom overnight. This method works because moving water rarely freezes and, when it does, it actually gives off heat. Often, flowers entirely cloaked in ice will suffer little or no damage, while those subject to the same degree of frost alone will die.
Be careful: new spring buds are susceptible to frost.
Some final tips for caring for your trees:
Once planted and established, a woody plant needs little care -- much less than most other plants. It has a few continuing needs to attend to, including mulching, feeding, watering, pest control, and pruning.
- Wrap the trunk of thin-barked trees, most notably fruit trees, in winter to help keep the bark from splitting. Tree wraps and firmer plastic tree guards can also discourage rabbits and rodents from chewing on the bark and can prevent accidental damage from mowers.
- Remove the tree wrap in the spring so it won't get too tight on the swelling trunk or provide a hiding place for pests.
- Adjust how you water a young tree as it gets established. When it is first planted and for the following growing season, provide water directly on the planting site. You can allow a hose to trickle gently over the root-ball, making a shallow saucer of soil below the leafy canopy to keep the water from running off.
- Once the tree is established enough for new roots to grow vigorously, use soaker hoses to water just outside the perimeter of the tree canopy. This will encourage the roots to spread outward, providing a stronger foundation for the tree.
- Mulch the tree properly. Put a layer of bark mulch, wood chips, or compost from the drip line (below the perimeter of the branch canopy) to 4 inches from the trunk (not too close or problems can arise). Mulching will help eliminate weeds and keep the planting site moist. It also looks good and gives the landscape a polished feel.
- Avoid excessively thick layers of mulch, which can limit soil aeration in heavy ground and cause roots to smother. Another problem occurs when thick heaps of mulch break down into rich organic matter. Shallow-rooted trees like maples can grow thick root mats in the mulch (which is not good), and some of those roots may start to girdle (which is even worse!). Shallow roots are also subject to excessive drying in summer.
- Help prepare evergreen trees for dry winter weather by watering them more in the fall, especially when rainfall has been limited. It's also helpful to spray leaves with an antitranspirant coating, which limits evaporation from the foliage.
- Don't plant salt-susceptible evergreens near the street in cold climates. Salt used for snow and ice control will splash up on the needles and drip into the soil. It won't be long before a thriving tree begins to brown out and then fail. Look for trees that can withstand salt spray. An example of a salt-susceptible evergreen is white pine. Some alternatives include sycamore maple, Austrian black pine, Japanese black pine, red mulberry, and sour gum.
- Prevent summer spider mite attacks on your evergreens by spraying susceptible plants with a hose every day during hot, dry weather. If you're out watering the garden, turn the hose on the evergreen foliage as well. Water helps dislodge spider mites and discourage their multiplication, a great nontoxic preventative.