String of hearts

Light and exposure

The string of hearts wants bright light to stay compact and colourful. The more it gets, the tighter and more marbled its leaves become, and the more its stems take on that beautiful purple tone. A bright spot near a window is ideal, with a little gentle morning sun that it enjoys, sheltered from the full summer sun that can scorch its thin leaves.

Starved of light, it stretches quickly: the leaves spread out along the stem, lose their marbling and the plant goes bare. In our dim Belgian winters, give it the brightest window in the house. Hung in front of an east- or west-facing bay window, it feels at home and unfolds like a curtain over the months.

Watering

Keep one thing in mind: the string of hearts would always rather be thirsty than overwatered. Its stems and small tubers store water, and it sails through long dry spells with ease. Water only when the substrate is completely dry, then give it a proper soak before letting all the excess drain away and emptying the saucer. In between, forget about it.

In autumn and winter, cut back to almost nothing; watering every three or four weeks is more than enough in the weak light. Overwatering is by far the number one cause of death: the stems go soft, blacken at the base and collapse. Slightly hollowed leaves point to normal thirst, easy to fix, whereas soft translucent stems signal rot that has already set in.

Soil and repotting

A very free-draining substrate is essential. Use a mix for cacti and succulents, or make your own by cutting indoor potting soil with a third of coarse sand, perlite or lava rock. Water must pass through fast and never sit around the tubers.

The pot matters as much as the soil. Choose a container with drainage holes, rather small, because the plant likes to be a little cramped and a large volume of soil stays wet too long. Terracotta is a good choice: it lets the substrate dry between waterings and limits the risk of rot, the main enemy of this succulent.

Temperature and humidity

The string of hearts is happy in ordinary household temperatures, between 18 and 24 degrees in spring and summer. It tolerates a little winter coolness, around 15 degrees, which marks a useful pause, but no lower than that.

In Belgium the rule is clear: it is frost-tender and cannot take the cold. You never leave it outside for long, and a spot in the garden in summer is only worth trying in real heat, bringing it back in well before the cool nights of late August. Below 10 degrees it suffers, so keep it away from icy panes in winter and from cold draughts near doors.

Pruning and upkeep

Upkeep comes down to very little. You shorten a stem that has grown too long or bare by cutting just above a pair of leaves, which pushes the plant to branch out and thicken. Do not throw away the cut pieces, they all root.

If the plant has stretched from lack of light, a firm prune in spring rejuvenates it: it comes back denser from the base. You can also wind the long vines around the pot or a support, or replant their tips in the same pot to fill it out. Remove the few dry leaves that stay clinging on as you go.

Pests and diseases

Indoors it is very healthy and most problems come from water. Overwatering causes the stems and tubers to rot: the base blackens, the vines go soft and drop off. At the first signs, cut away everything affected, let it dry and repot dry in fresh substrate, or save the plant by taking cuttings from still-firm sections.

As for pests, watch for mealybugs, those white cottony clusters hidden in the leaf axils and along the stems, common in the dry air of heating. A cotton bud soaked in alcohol deals with them, to be repeated each week. Aphids may target the rare flower buds, without harm, a rinse is enough.

Propagation

It is one of the easiest plants to propagate, almost child’s play. The simplest method: spot the small aerial tubers, those round swellings that form along the stems, and lay them on a moist free-draining substrate without detaching them from the mother plant. They root within a few weeks, then you cut the link.

Stem sections work just as well. Cut a piece with several leaves, let the cut dry for a day, then lay the stem on the substrate, burying the nodes, where the roots will emerge. Spring and summer are the best season. Within a few months, a handful of cuttings gives a well-filled pot, ideal to give away.

Month-by-month care calendar

Green Hub tips

• When in doubt, do not water. The string of hearts dies far more often from overwatering than from drought, especially in winter.
• To propagate it effortlessly, lay its small aerial tubers on the soil without detaching them: they root on their own within a few weeks.
• A plant that goes bare and loses its marbling is asking for more light: move it closer to the brightest window.
• Hang it or raise the pot to let the vines trail down, that is when it looks its best.
• Always use a well-draining cactus soil and a pot with holes: soil that stays wet is its worst enemy.