Oxydendrum
( ok - sih - DEN - drum )
At-A-Glance Information
|
Commonly called Sourwood or Sorrel Tree, this species of deciduous trees needs full sun and regular water. They are native to the eastern United States, and provide year-round interest through their foliage, fall color, and flowers. They slowly reach between 15 and 30 feet tall (eventually topping out around 50 feet given enough room) and spread to 20 feet wide. Leaves are tinted bronze early in springtime, mature to rich green in summer, and turn orange, scarlet, and dark purple in the fall. Fragrant flowers appear in summertime, clothing the tree in drooping white clusters. Blooms are followed by seed capsules that ripen from green to silver-grey, and stay on the tree through the late winter months. Use these trees as specimens in woodland gardens, or as patio shade trees. They can also be grown in containers when they are young, but will have to eventually be transplanted into the ground. Sourwood trees grow well in zones 2b-9 and 14-17. To find your zone, click here: Zone Map.
|
Caring for and pruning oxydendrum Trees
Plant Sourwood trees in a spot in the garden that receives full sun to partial shade. The more sun these trees receive, the more profuse flowering they will exhibit. Fall color is also more intense in sunny spots. The best time to plant these trees is in spring or fall to allow for roots to establish themselves before any extremes in temperature. These trees prefer acidic, well-draining, and loamy soils, ideally with a pH of 5.0 to 5.5. Apply a thick layer of mulch around the base of trees to suppress weed growth, increase soil moisture retention, and help to regulate soil temperatures. Water new plantings regularly as they develop strong root systems. During dry spells, make sure to provide extra deep waterings. Established trees are not drought-tolerant, and perform best with consistent moisture. Water deeply, especially during long dry periods of the year, and allow soil to dry out somewhat between waterings to discourage fungal root rot issues.
These trees do not require heavy feedings and typically do well with a simple application of organic compost to their root zone yearly in springtime. If trees seem to be struggling or foliage is somewhat discolored, trees may benefit from an extra feeding with a fertilizer made for acid-loving plants. A fertilizer formulated for azaleas or rhododendrons is ideal for this task. Avoid over-fertilizing trees, which can harm trees and encourage weak growth, as well as reduce flowering for the year. These trees also don't require heavy prunings, and have a natural pyramidal shape. Prunings should focus on maintaining this form instead of changing it. In late winter or early springtime, remove dead, broken, or diseased branches and lightly shape the canopy by removing crossing or poorly placed branches. Don't prune off too much foliage at any one time, as this can damage the tree and open it up to attacks from pests and disease.
These trees do not require heavy feedings and typically do well with a simple application of organic compost to their root zone yearly in springtime. If trees seem to be struggling or foliage is somewhat discolored, trees may benefit from an extra feeding with a fertilizer made for acid-loving plants. A fertilizer formulated for azaleas or rhododendrons is ideal for this task. Avoid over-fertilizing trees, which can harm trees and encourage weak growth, as well as reduce flowering for the year. These trees also don't require heavy prunings, and have a natural pyramidal shape. Prunings should focus on maintaining this form instead of changing it. In late winter or early springtime, remove dead, broken, or diseased branches and lightly shape the canopy by removing crossing or poorly placed branches. Don't prune off too much foliage at any one time, as this can damage the tree and open it up to attacks from pests and disease.
Propagation
Oxydendrum can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. Growing these trees from cutting is notoriously difficult and overall seed propagation is the preferred method. To propagate your Oxydendrum tree, follow the instructions below:
Propagating Oxydendrum by Cutting
Propagating Oxydendrum by Seed
Propagating Oxydendrum by Cutting
- Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
- In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Scrape a 1/2 inch long and 1/4 inch wide section of bark off of the bottom of the cutting. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot so that about half of the height of the cutting is under the soil surface. Fill in soil around the cutting to support it, but do not pack it down too much.
- Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
- Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.
Propagating Oxydendrum by Seed
- Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
- Harvest your seeds in fall. Seeds are contained inside of capsules that open up with they are ripened. Remove the seeds from their pods, and lay them out. To test for viability, place seeds in a bowl and fill it with lukewarm water. Viable seeds will sink, and the ones that float can be discarded. Seeds can be sown at this point, or can also be dried and then stored in a cool, dark, dry area.
- Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
- Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.
Oxydendrum seed pods turn brown and open up, spilling their contents.
|
Oxtdendrum seeds are small, thin, and light.
|
Problems and Pests
Oxydendrum trees can suffer from the following issues in the landscape, though they are typically free of serious pests or diseases:
- Fall Webworm
- Twig Blight
- Leaf Spot
- Root Rot
Gallery
When these trees take on colorful hues in cooler temperatures, they are a sight to behold.
|
Flowers of Oxydendrum trees are white, and bloom in pendulous infloresences.
|
Oxydendrum fall foliage is bright red.
|
Videos
|
All about these gorgeous trees.
|
A quick video about these small landscape trees.
|
|
How to identify Oxydendrum arboreum trees.
|
A Tree of the Week video about Sourwood.
|
Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 468, Oxydendrum arboreum
If you have any questions, comments, concerns, or photos you’d like to add to the gallery, please let me know by sending me a message using the button below!
