Corynocarpus

( kor - in - oh - CARP - us )

At-A-Glance Information

This small genus is native to New Guinea, Australia, New Zealand, New Caledonia, and Vanuatu. These evergreen trees typically have a narrow, upright habit and dark glossy green foliage. Flowers appear on mature plants in springtime, followed by large decorative orange berries. These trees are wonderful in coastal gardens, as a privacy or windscreen hedge, or in containers. Take care when planting these trees out in the landscape, as they are toxic and can be dangerous for humans and animals.

Corynocarpus species and varietals

The genus Corynocarpus includes just five species and is the sole member of the plant family Corynocarpaceae. ​The genus name is derived from the Greek words for club ('koryne') and fruit ('karpos'). To find your zone, click here: Zone Map.

Corynocarpus laevigatus (New Zealand Laurel, Karaka)
This species of evergreen shrub or tree grows well in full sun to partial shade with regular water. Take care if planting this shrub in your garden, as the fruits produced are highly toxic. These plants can reach 20-40 feet tall and 5-15 feet wide. Leaves are dark green and very glossy and flowers are small and off-white. Fruit follows the blooms, but is toxic. Good in containers or in the ground grown as a screen or large background hedge. Cultivar 'Variegatus' has variegated foliage.

Corynocarpus rupestris (Glenugie Karaka)
This rare rainforest tree is found mainly in eastern Australia, and forms a small, dense, shrubby plant. Foliage has toothed to spined margins. Cream to greenish-white lowers bloom in winter and springtime, followed by round drupe fruits. 

Caring for and pruning corynocarpus Trees

Choose a spot in the garden that receives full sun to partial shade. These trees prefer well-draining fertile soil that is slightly acidic to neutral (with a pH of between 6.0 and 7.0). If soil is heavy or clayey, make sure to amend the planting area with plenty of organic material before installation. Water moderately, allowing soil to dry out slightly between waterings. Avoid overwatering, as soil that is too moist can cause issues with root rot. During spring and summertime, waterings can be increased to offset the additional heat and dry weather. Karaka trees are tolerant to mild frost conditions, but will thrive best when temperatures remain between 60 and 75 degrees Fahrenheit. These trees do not typically need to be fertilized other than a yearly application of organic compost. If trees seem to be struggling, an application of a slow-release balanced fertilizer once a month during the growing season may help support the year's new growth and flowering. Prune trees lightly in late winter or early springtime, simply to maintain a desirable shape and encourage bushier growth. Cut out any errant, damaged, or diseased growth at this time.

Propagation

​Corynocarpus 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 tree, follow the instructions below:

Propagating Corynocarpus by Cutting
  1. 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.
  2. 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 semi-hardwood 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.
  3. 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 months have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
  4. 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 Corynocarpus by Seed
  1. 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. 
  2. Harvest your seeds. The seed pods on Caesalpinia plants are pretty easy to spot, they're large and dangle from the branches, 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.
  3. Caesalpinia seeds have a hard coating that protects them, but this coating also makes it a little difficult to get them to germinate. We can help the process along by scarifying them with sandpaper (or simply rubbing them against an abrasive surface). Do this with as many seeds as you can; they will probably not all sow, and the ones that do will be of varying characteristics. The more seeds you plant, the more chances you will have to get the resulting shrub you want. Place your seeds in lukewarm water for six hours. Viable seeds will sink to the bottom, and non-viable seeds will float to the top. You can discard any seeds that float.
  4. 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.
  5. 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.
Corynocarpus seeds are contained inside of the bright orange fruits that are ripe between the months of January and April in the tree's native range.
The seeds of Karaka trees are large and toxic if ingested, so keep them away from curious hands and mouths when harvesting and sorting.

Problems and Pests

Corynocarpus trees are typically pest-resistant, but can have issues with the following, especially if grown indoors:
  • Aphids
  • Scale Insects
For more information on these issues, consult the following pages:
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Gallery

A botanical drawing of the Karaka tree.
These trees can form multiple trunks, and typically have smooth bark when they are young.
Karaka trees have greenish-white flowers.
These trees top out around 40 feet tall and have evergreen foliage, which makes them great shade trees.
On older trees, bark is grey-brown and fissured.
Fruits produced by these trees emerge green and ripen to orange before dropping.

Videos

Learn about these New Zealand natives.
All about Corynocarpus laevigatus.

Resources

How to Grow Corynocarpus laevigatus
How to Grow and Care for Corynocarpus
Corynocarpus laevigatus
Wikipedia: Karaka (tree)
Wikipedia: Corynocarpus
The New Sunset Western Garden Book: The Ultimate Gardening Guide (2012) - Page 266, Corynocarpus laevigatus
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!
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