Cestrum

cestrum

( SESS - trum )

At-A-Glance Information

This group of evergreen shrubs, commonly called Hammer Bush or Jessamine, produce bright flowers and grow quickly in sheltered areas of the garden. They need partial shade and regular water for best performance in the landscape. Hummingbirds and butterflies will frequent this bush and its showy, fragrant blooms, which are said to smell intoxicating, strong, and citrusy. These shrubs have arching branches and do well with frequent pinching and pruning after the flowering season has ended. They can be damaged by frost, but recover quickly and will bloom in the same season. Fruit follows flowers. Use these shrubs to add color and interest to mixed beds and borders, to fill bare spaces in the garden, or as members of pollinator beds. Take care when planting these in your garden, as they are poisonous to humans if ingested in large amounts. They are also considered invasive in certain regions of the world.

Cestrum Species and Varietals

The genus Cestrum includes between 150 and 250 species, and is a member of the family Solanaceae. The best growing zones for Cestrum vary depending on the species grown. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Cestrum aurantiacum (Orange Cestrum, Yellow Cestrum, Orange Jessamine, Orange-Flowering Jessamine)
Grows best in USDA hardiness zones 7b-11b or Sunset growing zones 16, 17, 21-24, H1 and H2. Native to Guatemala, this shrub grows to reach 8 feet tall and wide at maturity. Orange flowers appear in late spring and summer, followed by white berries. Leaves are green, and this species can be used as an espalier. Can spread by suckers, and will lose its leaves in cold temperatures. This species is considered to be an invasive plant in regions of Africa, Asia, New Zealand and Australia.

Cestrum elegans (Red Cestrum, Purple Cestrum, Crimson Cestrum, Elegant Cestrum, Elegant Poison-Berry)
Grows best in USDA hardiness zones 8-11 or Sunset growing zones 13, 17, 19-24, H1 and H2. This is a vining shrub that is native to Mexico, and grows to be 10 feet or more in height and width. Leaves are deep green and flowers are purplish-red. Red berries appear after the blooming period. Variety 'Smithii' has pink flowers. This species is considered invasive in southeastern Australia and New Zealand.

Cestrum fasciculatum (Early Jessamine, Red Cestrum, Early Flowering Jessamine)
This species is native to Mexico and grows well in USDA hardiness zones 8-11 or Sunset growing zones 13, 17 and 19-24. Very similar to Cestrum elegans but grows larger. Mature shrubs reach up to 12-15 feet tall and just as wide. Early Jessamine is considered invasive in New Zealand and Australia, and has been identified as problematic in California in the United States.

Cestrum nocturnum (Night Jasmine, Night-Blooming Jessamine, Lady of the Night, Queen of the Night)
This species grows best in USDA hardiness zones 9-11 or Sunset growing zones 13, 16-24, H1 and H2. Native to the West Indies, this shrub grows to be 12 feet tall and just as wide and has creamy white summer flowers. At night, this plant gives off a powerful fragrance. For best blooms, plant in full sun. This species is invasive in many tropical and subtropical areas around the globe, including Oceania and parts of the United States.

Caring for cestrum

Take care when planting these in your garden, as they are poisonous to humans if ingested in large amounts; they are also considered invasive in certain tropical and subtropical regions around the world. These plants are not frost-hardy; they will die to the ground in frost conditions but regrow, though in many areas are grown as annual shrubs. Plant in springtime, after the last danger of frost has passed. They prefer fertile soil that has a pH between 6.0 and 8.0 and is well-draining (loamy or sandy soils are great) and to be grown in full sun to partial shade. If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water new plantings regularly as they establish a strong root system in their new home. Keep the soil moist, but not wet, never allowing it to dry out completely once plants are mature.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Because Cestrum shrubs are fast-growing, they can really be pruned any time of the year to control shape and size, though the best time is in spring before new growth starts to emerge. These vining shrubs can be trained to grow arbors and trellises, or be espaliered along a fence if desired. They do not inherently need a structure to climb however, naturally forming a sprawling, arching shrub. Cestrum can survive in the landscape for between 3 and 20 years or more before needing to be replaced. Most are grown as long-lived evergreen or deciduous shrubs in the landscape in suitable climates.

Caring for Cestrum in Containers
Cestrum shrubs thrive when grown in the ground, but they can also be cultivated in containers on patios, balconies, or along walkways. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Cestrum plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every two or three years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

Caring for Cestrum Indoors
Cestrum grown indoors will need to be placed in an area that receives bright, indirect light. The best light is indirect sun from an east-, south-, or west-facing window. Choose a container that has a drainage tray underneath that can be filled with rocks; this will help to keep the area around the plant humid. The container should be 1-2 inches wider and deeper than the nursery pot or root ball. Fill with a well-draining substrate amended with perlite. Water regularly as the plant establishes itself in its new pot. At maturity, these plants appreciate consistently moist soil; as a general rule of thumb, water whenever the top inch of soil feels dry to the touch.

Propagation

Cestrum 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 Cestrum shrub, follow the instructions below:

Propagating Cestrum 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. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring, 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 3-4 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 (between 70 and 75 degrees Fahrenheit), sunny conditions indoors (but not in direct sunlight). Water whenever your soil is dry under the top layer. After about 1-2 months have passed, your cutting should be rooted. When you notice new growth on your propagated Cestrum, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 70-75 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 Cestrum by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of its parent. To propagate by seed, you will need gloves, a paper bag, a sealable container, an envelope, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Your seed harvesting time will depend on when your specific shrub flowers and goes to fruit (fall is usually a good time for harvesting). The seeds are contained in the fruits, and will be ready to harvest once the fruits have dried up and darkened on the shrub. Once this happens, you can harvest the seeds inside. With gloves on to protect your hands from possible irritation, 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. After a few days, shake the bag to release the seeds from their pods. Once they have been released, take them out of the bag and put them in an envelope inside of a sealable container. Handle carefully to avoid skin irritation. They will stay in this container until the next spring.
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 under the soil surface. Cover them with a light dusting of soil and water with your spray bottle. Place your tray of seeds in a warm area (70-75 degrees Fahrenheit) 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 (they should be about 6 inches tall), transplant them to their own individual 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 at a temperature of about 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.

Cestrum seeds.

Cestrum seeds are enclosed inside fruiting bodies.

Problems and Pests

Cestrum, or Jessamine, shrubs themselves can be considered pests, as they are invasive in many areas of the world. Check with local authorities before planting. Cestrum plants can have issues from time to time with the following pests and diseases: