Alnus glutinosa is a deciduous alder tree, 40 to 60 feet in height, 20 to 40 feet in spread; can reach 100 feet tall. Small trees are often multi-stemmed and pyramidal, can also develop an oblong or rounded irregular crown. Bark is a lustrous gray-green in young trees, older specimens have a polished brown coloration. Foliage is dark glossy green, can develop yellow fall color, more often leaves fall off green. Male flower is a reddish catkin, female is a purplish strobile, not conspicuous. Fruit is a winged nutlet, fall maturing. Prefers moist to wet soil , but adaptable to dry, it will seed itself if planted along stream banks. Nitrogen fixing species, does not require fertilization usually, not tolerant of heat. Subject to some pests, but not usually serious. Good choice for difficult, wet sites, infertile areas. Native to Europe, western Asia and Africa, naturalized in areas of the U.S. Several cultivars are available.
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Size:Height: 0 ft. to 60 ft.
Width: 0 ft. to 40 ft.
Tolerances:rabbits, slope, wind,
Bloomtime Range: Early Spring to Early Spring
USDA Hardiness Zone:3 to 7
AHS Heat Zone:Not defined for this plant
Light Range:Part Shade to Full Sun
pH Range:5 to 7.5
Soil Range:Some Sand to Mostly Clay
Water Range:Dry to Boggy
FertilizingHow-to : Fertilization for Established Plants
Established plants can benefit from fertilization. Take a visual inventory of your landscape. Trees need to be fertilized every few years. Shrubs and other plants in the landscape can be fertilized yearly. A soil test can determine existing nutrient levels in the soil. If one or more nutrients is low, a specific instead of an all-purpose fertilizer may be required. Fertilizers that are high in N, nitrogen, will promote green leafy growth. Excess nitrogen in the soil can cause excessive vegetative growth on plants at the expense of flower bud development. It is best to avoid fertilizing late in the growing season. Applications made at that time can force lush, vegetative growth that will not have a chance to harden off before the onset of cold weather.
LightConditions : Full to Partial Sun
Full sunlight is needed for many plants to assume their full potential. Many of these plants will do fine with a little less sunlight, although they may not flower as heavily or their foliage as vibrant. Areas on the southern and western sides of buildings usually are the sunniest. The only exception is when houses or buildings are so close together, shadows are cast from neighboring properties. Full sun usually means 6 or more hours of direct unobstructed sunlight on a sunny day. Partial sun receives less than 6 hours of sun, but more than 3 hours. Plants able to take full sun in some climates may only be able to tolerate part sun in other climates. Know the culture of the plant before you buy and plant it!
WateringConditions : Moist
Moist is defined as soil that receives regular watering to a depth of 18 inch deep, does not dry out, but does not have a drainage problem either.
PlantingHow-to : Staking Trees
Staking is done differently depending on the size and flexibility of the tree, and the windiness of the planting site. Generally only trees that are planted in windy, exposed locations need to be staked. For most trees, a low stake is preferred, to let the tree move naturally. For windy areas or flexible trees, use a high stake. For trees more than 12 feet tall, use two low stakes on opposite sides of the tree or several guy ropes. The ties used need to accommodate growth and not cause bark damage with friction. Buckle-and-spacer ties can be found at garden centers, they are expandable and have a protective spacer. Ties without spacers should be formed into a figure eight to create padding. Latest studies have shown that when staking a tree, provide enough leeway so that the tree can move back and forth in the wind. Stronger roots will develop this way. If the tree can not move back and forth, these important roots will not develop and the tree might fall over during a storm, once stakes are removed. When planting a tree, stake at the time of planting if staking is a necessity.
How-to : Planting a Tree
Dig out an area for the tree that is about 3 or 4 times the diameter of the container or rootball and the same depth as the container or rootball. Use a pitchfork or shovel to scarify the sides of the hole.
If container-grown, lay the tree on its side and remove the container. Loosen the roots around the edges without breaking up the root ball too much. Position tree in center of hole so that the best side faces forward. You are ready to begin filling in with soil.
If planting a balled and burlaped tree, position it in hole so that the best side faces forward. Untie or remove nails from burlap at top of ball and pull burlap back, so it does not stick out of hole when soil is replaced. Synthetic burlap should be removed as it will not decompose like natural burlap. Larger trees often come in wire baskets. Plant as you would a b&b plant, but cut as much of the wire away as possible without actually removing the basket. Chances are, you would do more damage to the rootball by removing the basket. Simply cut away wires to leave several large openings for roots.
Fill both holes with soil the same way. Never amend with less than half original soil. Recent studies show that if your soil is loose enough, you are better off adding little or no soil amendments.
Create a water ring around the outer edge of the hole. Not only will this conseve water, but will direct moisture to perimeter roots, encouraging outer growth. Once tree is established, water ring may be leveled. Studies show that mulched trees grow faster than those unmulched, so add a 3"" layer of pinestraw, compost, or pulverized bark over backfilled area. Remove any damaged limbs.
ProblemsPest : Mealybugs
Small, wingless, dull-white, soft-bodied insects that produce a waxy powdery covering. They have piercing/sucking mouth parts that suck the sap out of plant tissue. Mealybugs often look like small pieces of cotton and they tend to congregate where leaves and stems branch. They attack a wide range of plants. The young tend to move around until they find a suitable feeding spot, then they hang out in colonies and feed. Mealybugs can weaken a plant leading to yellow foliage and leaf drop. They also produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface fungal growth called sooty mold.
Prevention and Control: Isolate infested plants from those that are not. Consult your local garden center professional or the Cooperative Extension office in your county for a legal insecticide/chemical recommendation. Encourage natural enemies such as lady beetles in the garden to help reduce population levels of mealy bugs.
Pest : Aphids
Aphids are small, soft-bodied, slow-moving insects that suck fluids from plants. Aphids come in many colors, ranging from green to brown to black, and they may have wings. They attack a wide range of plant species causing stunting, deformed leaves and buds. They can transmit harmful plant viruses with their piercing/sucking mouthparts. Aphids, generally, are merely a nuisance, since it takes many of them to cause serious plant damage. However aphids do produce a sweet substance called honeydew (coveted by ants) which can lead to an unattractive black surface growth called sooty mold.
Aphids can increase quickly in numbers and each female can produce up to 250 live nymphs in the course of a month without mating. Aphids often appear when the environment changes - spring & fall. They're often massed at the tips of branches feeding on succulent tissue. Aphids are attracted to the color yellow and will often hitchhike on yellow clothing.
Prevention and Control: Keep weeds to an absolute minimum, especially around desirable plants. On edibles, wash off infected area of plant. Lady bugs and lacewings will feed on aphids in the garden. There are various products - organic and inorganic - that can be used to control aphids. Seek the recommendation of a professional and follow all label procedures to a tee.
Diseases : Pythium and Phytophtora Root Rot
Rot Rot, Pythium or Phytophthora occurs when soil moisture levels are excessively high and fungal spores present in the soil, come in contact with the susceptible plant. The base of stems discolor and shrink, and leaves further up the stalk wilt and die. Leaves near base are affected first. The roots will turn black and rot or break. This fungi can be introduced by using unsterilized soil mix or contaminated water.
Prevention and Control Remove affected plants and their roots, and discard surrounding soil. Replace with plants that are not susceptible, and only use fresh, sterilized soil mix. Hold back on fertilizing too. Try not to over water plants and make sure that soil is well drained prior to planting. This fungus is not treatable by chemicals.
Rhizoctonia Root and Stem Rot symptoms look similar to Pythium Root Rot, but the Rhizoctonia fungus seems to thrive in well drained soils.
MiscellaneousGlossary : Tree
Tree: a woody perennial with a crown of branches that begin atop a single stem or trunk. The exception to this rule is multi-trunk trees, which some may argue are really very large shrubs.