HowStuffWorks Answers Your Gardening Questions

Tree Questions

Only female holly produces berries.
Only female holly produces berries.

If you have questions about trees, we've got answers. Trees require different care and maintenance than plants. They also develop different symptoms of illness. If you want to know how to plant, prune, and protect your trees, read on.

Q: Why does my wisteria never bloom? It grows so quickly that it must be pruned often.

A: You may be pruning off next year's flower buds. Encourage short side shoots for flower buds by partially pruning the longest side branches. To avoid excessive growth, do not fertilize wisteria. Wisteria blooms best with ample exposure to the sun. Root pruning may shock the plant into flowering -- in June, use a spade to cut a six-inch deep circle about two feet from the base of the plant.

Q: When should I prune my trees?

A: Pruning shade and ornamental trees not only adds to the aesthetics of the landscape, but prolongs the life of the tree. Prune to thin out branches in late winter when the sap is rising. The sap "bleeding" helps prevent disease organisms from entering the wound and the tree will heal quickly at this time of year. Limbs that need to be removed because of storm or disease damage can be pruned any time of year.

Q: To receive more light into the yard, should I have the trees topped?

A: Topping not only disfigures a tree aesthetically, but drastically degrades its long-term health. The large, open wounds that topping creates will not heal completely, allowing easy entrance to disease-causing organisms. Rapid, dense, shoot growth (called suckers) grow to the original height of the tree, consequently defeating the purpose of topping. The new growth will not be as structurally sound as normal branching, becoming more susceptible to storm damage.

Q: I have several hydrangeas, all of which are the same kind. Why are some blue flowering while others are pink?

A: The availability of aluminum in the soil, determined by the soil's pH, determines the color of your type of hydrangea. If the pH is high (7.0 or above), the flowers will be pink. Blue flowers develop from acidic soil (4.5 to 5.5), and purplish flowers in between. To ensure blue flowers, lower the pH with a sulfur-based product. Raise the pH with lime for pink blossoms.

Q: Can a live Christmas tree be planted after the holidays?

A: Yes. Prepare the hole well before the ground freezes. Amend the loose soil as you dig so it will be ready for planting, and store the soil where it will not freeze. Choose a tree with a tight, solid root-ball and wrap the ball in plastic to keep moist while it's in the house. A cool room for no more than a week is advised. Plant the tree as soon as possible; mulch and water well.

Q: What causes the bark of young trees to crack, and how can it be corrected?

A: The vertical cracking, or sunscald, appears on the southwest side of the trunk; where the tree heats up on warm, sunny, winter days, and freezes rapidly when the sun sets. Young trees are most prone to sunscald because of their thin bark. These cracks provide a path for diseases and insects. Sunscald can be prevented by wrapping the trunk in a protective covering for the winter. Expandable, white plastic tree wraps are available at garden centers.

Q: What makes some hollies produce berries when other don't?

A: Hollies are either male or female; only the females produce berries. A pollen-producing male plant needs to be growing nearby to pollinate a female, otherwise berries will not form. Although some species can pollinate other species, it's generally necessary to have both a male and a female of the same type. Other reasons for lack of fruit include a shortage of sunlight where the female is planted, or severe drought while berries are forming.

Q: Is it possible to transplant trees from the woods to the yard?

A: Although it's possible, the success rate is low. Forest tree roots are quite entangled with other trees; either with wide-spreading shallow roots, or a deep taproot, depending upon species. The tree is already acclimated to the woods exposure. Both the shock of transplanting and the loss of roots often kill the tree. Nursery-grown trees have been tended by root pruning to encourage the development of a small but concentrated root system, making transplanting more successful.

Q: Is it possible that road salt is killing the shrubs at the end of my driveway?

A: Salt toxicity is common in areas where deicing salts are used in winter. The worst damage occurs right where the salt is applied, near roads and walks. Plants will display general dieback, yellowish foliage, and weak growth. Wash salt residue from plants with a hose, and soak the soil to leach the salt from the beds. Don't use salts around the home. Some fertilizers can be safely used to melt ice and will not harm nearby plants.

Q: Is it necessary to stake newly planted trees?

A: If the crown of the tree is relatively large compared to the size of the root ball, staking may be needed to prevent the tree from tilting as it settles. Be sure the root ball sits on a firm soil base. Tie with flat plastic guy string or wire covered in old garden hose to protect the bark from being cut or wounded. Remove stakes and wires as soon as the tree roots become established. Evergreen trees do not usually require staking.

Want to find out more about growing a flower garden, a houseplant, or a vegetable garden? Check out: