Lagunaria
( lah - goon - AIR - ee - uh )
At-A-Glance Information
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Commonly referred to as Cow Itch Tree or Primrose Tree, this genus of evergreen tree is native to the South Pacific and Australia, and grows best in zones 13, 15-24, H1 and H2 (To find your zone, click here: Zone Map). The genus Lagunaria is a member of the plant family Malvaceae and includes just 2 species, only one of which (Lagunaria patersonia) is commonly cultivated. These trees need full sun and regular waterings, and quickly reach 30 feet tall and wide. Foliage is dense, and pinkish rose flowers bloom in summertime, and fade to white with age. Seed capsules are popular in arrangements, and eventually split open to reveal bright brown seeds. Variety 'Royal Purple' has purple blossoms. Use these as specimen trees or grouped together for windbreaks or screens. Take care if planting this tree in your yard, as the seed pod fibers can irritate skin and eyes.
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Caring for and pruning lagunaria Trees
Lagunaria trees are relatively hardy tropical trees that can thrive in a variety of environments, but they do have some specific care requirements to flourish. These trees prefer to grow in full sun, meaning they should be in a spot that receives at least 6 hours of direct sunlight each day. Lagunaria can tolerate partial shade, but will not flower as profusely. The more sun they get, the more flowers will be produced. These are heat-tolerant plants that are ideal for warm areas. Lagunaria prefers soil to be well-draining soil that is sandy or loamy. If local soils are overly clay or compacted, they will not grow well. If this is the case, amend the planting area with plenty of organic material and/or sand before planting. The ideal soil pH for growing Lagunaria is between 6.0 and 7.0 (neutral to acidic). Apply a thick layer of mulch around plantings to increase soil moisture retention, suppress weed growth, and regulate soil temperatures. After planting, make sure young trees receive regular waterings to help them establish a strong, healthy root system. Mature trees should be deep watered to encourage a root system that stretches farther down into the soil. Avoid overwatering these plants, as they do not like to have wet feet, and will develop root rot issues. Allowing soil to dry out between waterings will lessen the chances of fungal diseases taking hold.
These trees benefit from light pruning after flowers have faded to shape and remove any dead, damaged, diseased, or crossing branches. Regular prunings can help to maintain a handsome shape, especially when grown as a shrub. If a tree habit is desired, prune up the lower branches on young plants to encourage a single leader to take hold. Avoid drastic pruning or cutting back, as this can hinder flower production for the next season, as well as open the tree or shrub up to diseases and pests. These trees don't need to be fertilized; a simple application of organic compost around the base of the tree at the beginning of springtime is typically sufficient to provide nutrients for growth and flowering. If trees are struggling, or if soil is particularly poor, trees may benefit from a feeding with a balanced, slow-release fertilizer (such as a 10-10-10) in spring. Avoid over-fertilizing trees, as doing so can result in excessive foliage growth at the expense of flowering.
These trees benefit from light pruning after flowers have faded to shape and remove any dead, damaged, diseased, or crossing branches. Regular prunings can help to maintain a handsome shape, especially when grown as a shrub. If a tree habit is desired, prune up the lower branches on young plants to encourage a single leader to take hold. Avoid drastic pruning or cutting back, as this can hinder flower production for the next season, as well as open the tree or shrub up to diseases and pests. These trees don't need to be fertilized; a simple application of organic compost around the base of the tree at the beginning of springtime is typically sufficient to provide nutrients for growth and flowering. If trees are struggling, or if soil is particularly poor, trees may benefit from a feeding with a balanced, slow-release fertilizer (such as a 10-10-10) in spring. Avoid over-fertilizing trees, as doing so can result in excessive foliage growth at the expense of flowering.
Propagation
Lagunaria trees and shrubs 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. To propagate your shrub or tree, follow the instructions below:
Propagating Lagunaria by Cutting
Propagating Lagunaria by Seed
Propagating Lagunaria 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. 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. 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 6-8 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 Lagunaria 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. Take precautions to protect yourself from skin contact with the hairs that cover seed pods.
- Harvest your seeds. The seed pods on Lagunaria plants are pretty easy to spot, they're large and are left behind after flowers have faded. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
- 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.
Lagunaria seed pods.
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Seeds are bean-shaped and reddish-brown.
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Problems and Pests
Lagunaria trees typically have issues with the following pests and diseases:
- Asian Longhorned Beetle
- Lymantria Dispar Moth
- Giant African Snail
- Thrips
- Phytophthora austrocedri
- Oak Processionary Moth
- Anthracnose
- Aphids
Gallery
These large trees can reach up to 50 feet tall but are usually seen more around between 20-30 feet tall.
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Flowers are pink.
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Seed pods remain on the tree after flowers fade.
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Videos
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Learn about Norfolk Island Hibiscus.
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All about why these trees can be a little obnoxious.
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Resources
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 397, Lagunaria patersonii
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