The string of hearts (Ceropegia woodii) is also known as chain of hearts, collar of hearts, rosary vine, and sweetheart vine. It has developed flower shapes that are incomparable in complexity with any other flower.
Due to their particular specialization in environmental conditions, the plants require little care. With regard to the choice of location and substrate, you need to consider a few factors so that candlestick flowers feel comfortable.
Both the plant genus Ceropegia and the species Ceropegia linearis subsp. woodii are referred to as string of hearts. It is a popular ornamental plant that you will often find under the name Ceropegia woodii.
The string of hearts belongs to the dogbane family (Apocynaceae). The natural range of the subspecies cultivated as ornamental plants is limited to the subtropical regions of South Africa.
Other subspecies of Ceropegia linearis also occur in Mozambique, Zimbabwe, and Malawi as far north as Kenya.
Ceropegia woodii has fleshy thickened deciduous leaves that serve as water reservoirs. These succulent leaves divide into a lanceolate to cordate leaf blade and a petiole three to ten millimeters long.
The leaves may be more or less round in shape. The blade ends in an acuminated point and is dark green on the upper side. The underside of the leaf appears light green and often has a red tinge.
The small leaves sit opposite on the shoot and have a high ornamental value due to their silvery-white grain.
The string of hearts owes its name to the conspicuously shaped flowers. These are hermaphroditic and have an axis of symmetry.
Each flower reaches a length between 0.8 and 1 inch (2 and 2.5 cm). Their petals fuse together and form a corolla cup, which merges into the corolla tube with a visible constriction.
The corolla cup is spherical to oval in shape and about four millimeters wide. The corolla tube has a diameter of two millimeters.
While the corolla cup is colored greenish-white to whitish-purple with dark purple veining, the corolla tube appears light purple or purple striped.
It is often whitish dotted or reticulated at the upper end. Its light green to purple corolla lobes curve inward. They fuse together like umbrellas at their tips.
The flower anatomy is reminiscent of small lampshades. The string of hearts pursues a special purpose with this flower shape. It exudes an odor that attracts small flies. These get lost in the corolla tube, where they are trapped by the small hairs.
The flies pollinate the first mature female flower organs with the pollen packets they bring with them. Then the male organs mature and produce new pollen, which the flies pick up by moving around in the flower.
The hairs in the flower mouth slacken, allowing the flies to escape again.
Ceropegia woodii develops root tubers that thicken spherically and have a rough surface. As the plant ages, the rootstock becomes more vigorous. The rootstock sprouts twining, creeping, or pendulous shoot axes that can reach 40 inches (100 cm) in length.
These shoot axes are very thin, with a diameter of between one and two millimeters. Older specimens form small white nodules in the leaf axils, which serve for vegetative propagation.
Strings of hearts are ideal hanging basket plants. The green curtain of shoots and leaves is an interesting eye-catcher in hanging pots.
However, tall containers such as vases, old copper pitchers, or zinc tubs are also perfect for creating green plant arrangements with a string of hearts.
You can shape the shoots of the succulent plant as you like. For example, you can grow the plant in a heart shape or as a trellis. Use bendable wires to direct the shoots in the right direction.
Is the String of Hearts Poisonous?
There is no known information about possible toxic ingredients. The string of hearts carries a transparent to whitish milky sap in its root bulb and plant parts that should prove harmless.
Sensitive individuals should take precautionary care, though, wearing gloves to prevent possible skin reactions. There is also no known danger to animals from eating the plant.
Many dogbane plants, which include the string of hearts, are poisonous. It is better not to cultivate them within reach of children and pets.
If you decide to grow this plant, place it in inaccessible places as a precaution. But also keep in mind that the shoots can grow very long.
The pendulous shoot axes pose a potential danger to cats. Cats can easily catch them while playing and pull down the pot.
What Location is Suitable for the String of Hearts?
The string of hearts needs a bright place where there is a normal room temperature. Avoid places that are in full sun.
Succulent plants are sensitive to direct sunlight, especially during midday hours. Though, it aids flower development if the plant gets some sun during the morning and evening hours.
Strings of hearts do not require special humidity. They thrive well even in dry air. In summer, the plant gratefully appreciates an outdoor location.
What Kind of Soil Does the String of Hearts Need?
Ceropegia woodii prefers a low-nutrient and highly permeable substrate. For higher permeability, you can mix 60 percent soil with 40 percent loose mineral material.
For this purpose, beads of expanded clay, sand, perlite, pumice gravel, or lava granules are suitable.
These mineral admixtures provide better air circulation, as they increase the crumb structure of the substrate. They also store nutrients and moisture, which they gradually release into the substrate.
This substrate is suitable for cultivation:
- Cactus soil
- Pot plant soil
- Seedling soil
Propagating the String of Hearts
Strings of hearts are most easily propagated via their tubers, which develop in the leaf axils. This propagation method is possible during the main growth period from spring to fall.
Pick off the tubers and scatter them on a suitable substrate. Cover the tubers with a layer of quartz sand, which prevents rotting.
Place the pot in a shady place where temperatures range from 60 to 65 °F (16 to 18 °C). Make sure that the soil is constantly moist.
Sowing the String of Hearts
Once your plant has developed fruit, you can use the seeds inside for propagation. Fill a plastic pot with a suitable growing medium, which you loosen up with mineral admixtures.
Spread the seeds evenly over the soil and cover larger seeds lightly with the substrate. Small seeds can lie freely.
Put a transparent plastic bag or foil over the pot to keep the humidity constant. To prevent mold growth, consider aerating daily. On this occasion, also add a little fresh water to the substrate.
The seeds will germinate well in this location:
- Semi-shaded on the windowsill or in a mini-greenhouse
- Temperatures between 74 and 82 °F (23 and 28 °C) during the day
- 68 to 72 °F (20 to 22 °C) are ideal at night
Cut shoots between 3 and 4 inches (8 and 10 cm) long from the plant and let the cuttings air dry for a few days. Then, remove the lowest leaves and put the shoots on a sandy substrate.
The cuttings will feel most comfortable in slightly moist soil. Water them sparingly and allow the top layer to dry between watering units.
The location should be bright and ensure temperatures between 60 and 65 °F (16 and 18 °C). After seven to eight weeks, the first roots have developed.
The String of Hearts in a Pot
Choose a pot that provides adequate space for the root system. The string of hearts thrives better in shallow pots than in deep containers.
When choosing a pot, you should make sure that it has enough room for drainage. It should have a drainage hole to allow water to drain away. Cover the bottom with shards of clay and then fill the container with the substrate.
Ceropegia woodii develops a fine root system, on which numerous tubers form. These thickenings not only serve as water and nutrient storage but also perform photosynthetic functions.
For energy conversion, the roots need some light. Cover the root system only lightly with a sandy layer, which should not exceed a thickness of half an inch (1 cm).
The String of Hearts On a Balcony
During the summer months, you can safely place the string of hearts on the balcony or terrace. A place in partial shade is ideally suited, as the leaves are sensitive to direct sunlight.
Watering the String of Hearts
Strings of hearts are specialists when it comes to watering. They store moisture in their thickened plant parts and draw on these reserves during dry periods.
You only need to water your string of hearts moderately. Allow the soil to dry out between waterings.
The plant does not tolerate waterlogging. Pour out the excess water in the saucer after five minutes at the latest.
Watering the String of Hearts in Winter
Reduce watering to a minimum during the dormant period so that the root ball does not dry out. Use the room temperature of the winter quarters as a guide.
The cooler it is, the less often you need to water the plant. Rainwater is absolutely suitable for watering the string of hearts. But you can also use tap water, provided that it is not too calcareous.
Fertilizing the String of Hearts Properly
You should only fertilize the plant sparingly, as its nutrient requirements are low. Mature and healthy plants do well with a fertilizer every four weeks between spring and fall.
Cactus fertilizer is a good source of nutrients, administered in weak concentrations with the water used for watering. If the string of hearts goes into its dormant mode during the winter, you do not need to continue fertilizing the plant.
Pruning the String of Hearts Properly
You can prune the string of hearts year-round if the shoots become too long. But it is a good idea to do major pruning in the spring so that the plant regenerates quickly afterward.
Heavy pruning will cause the plant to develop numerous new shoots. This stimulates the breeding tubers to sprout.
How to Repot the String of Hearts
Once the root system has spread throughout the pot, you should repot the string of hearts.
Young plants will take a few years before the space becomes too tight. You can repot older plants annually, though. The best time to do this is in the spring, just before the end of winter dormancy.
Starting in November, the string of hearts goes into hibernation, which lasts until February. The succulent plant likes to spend the winter in a cooler place indoors.
Place the container in an unheated stairwell or in a rarely used room. Temperatures should be between 54 and 65 °F (12 and 18 °C). If the temperature drops below 46 °F (8 °C), the string of hearts may suffer.
The cold period is important for the plant to develop flowers next spring. During this period, you should reduce the care measures to a minimum.
Strings of hearts are robust plants that rarely suffer from diseases. Common symptoms of damage are usually rather due to care errors.
Waterlogging is the biggest enemy of the plant because it leads to root rot. If you don’t detect waterlogging quickly enough, the plant may die.
If the leaves suddenly wilt or turn a pale green color, the cause may be an infestation of fungi of the genus Phytophthora. These fungi are considered aggressive opportunistic parasites.
Once they have colonized a host plant, it usually does not survive the infection. You should remove the infected plant to prevent the fungus from spreading to other plants in the area.
Phytophthora colonizes rotten parts of plants. The fungi are often involved in root rot and further accelerate rotting processes.
As a preventive measure, make sure that waterlogging does not form in the substrate. Overfertilization also favors the living conditions of the fungal spores.
The string of hearts is mostly attacked by pests that feed on the sap of the plants. If you don’t treat the infestation in time, it will weaken the plant increasingly.
The pests leave a sticky film on the leaves. This honeydew provides optimal growth conditions for sooty mold fungi. These fungi look unsightly but do not damage the plant further.
Aphids prefer to reproduce during dry summer months. Healthy plants are less susceptible to these pests. If aphids infest your plant, you can remove them easily with a sharp stream of water.
Neem preparations are also helpful if you have a larger infestation.
These pests appear occasionally and leave behind white webs that resemble cotton balls. They suck the plant sap and inject the plant with toxic substances that affect its growth.
Infested leaves turn yellow and curl up until they eventually fall off. Plants weakened by care mistakes are especially susceptible to pest infestation.
Place affected plants in a bright, cool place and spray the plant parts with an antidote.
A well-working antidote against mealybugs:
- 1 Tbsp (15 ml) spirit
- 0.25 gal (1 l) water
- 1 Tbsp (15 ml) curd soap, dissolved curd soap, or kerosene oil
- Variegata: Silvery-white striped leaves with pink edges, vigorous growth. Shoots pendulous, height of growth up to 20 inches (51 cm).
- Ceropegia sandersonii: String of hearts with climbing shoots. Flowers are up to 3 inches (7 cm) tall, light green with white stripes and dark green speckles. Shoots up to 6.5 ft (2 m) long.