Heartleaf philodendron

Light and exposure

The philodendron likes bright but filtered light, never direct sun which scorches and bleaches its leaves. A spot near an east or west window, or set back from a south window, suits it very well. That is where the leaves stay large, deep green and close together.

It tolerates partial shade better than most plants, which makes it a good choice for a slightly dark corner, but then its growth slows and the stems stretch out with more widely spaced leaves. Under our weak winter light, from November to February, move it closer to a bright window to stop it running into bare, leggy stems.

Watering

Let the top two centimetres of the substrate dry out before watering again, which means roughly once a week in spring and summer, then every ten to fifteen days in winter. The philodendron copes better with a slight lapse than with too much water.

Empty the saucer after each watering: roots left standing in water rot quickly. Yellow leaves dropping in series generally signal too much water, whereas soft, brown leaves that are dry at the edge point instead to a lack of water or to the overly dry air of winter. A finger in the soil remains the best guide.

Soil and repotting

A potting mix for green plants, lightened with a handful of orchid bark and perlite to stay airy, is perfect. Like all aroids, the philodendron hates compact substrates that hold water. The pot must have drainage holes.

Repot in spring every two years, or when the roots spill out through the drainage holes, into a pot only slightly larger. Too large a volume of soil stays wet too long and rots the roots. If the plant is in a hanging basket and hard to repot, simply renew the surface soil each spring.

Temperature and humidity

The philodendron is happy between 18 and 26 degrees. Below 13 degrees, growth stops and the leaves may blacken or drop. It withstands no frost at all. Keep it away from the cold draughts of doors and single-glazed windows, as well as from scorching radiators.

The Belgian challenge is twofold in winter: the cold, which must be avoided, and above all the air dried out by central heating from November to March, which browns the leaf edges. A little moisture in the air, regular misting or the pot set on damp clay pebbles, helps it get through the season in good shape.

Pruning and upkeep

Pinch the stem tips in spring to force the plant to branch and stay bushy rather than running into long bare stems. Do not throw away the cut pieces, they root easily and let you fill out the pot.

Cut back to the base any bare stems or yellowed leaves. You can train the stems up a moss stake for a climbing habit, where the leaves grow larger, or let them cascade from a hanging basket. Wipe the leaves from time to time to remove dust and capture the light.

Pests and diseases

In winter, in dry air, watch for spider mites (Tetranychus urticae), which speckle the leaves with yellow and spin fine webs, and mealybugs, white cottony clusters in the leaf axils. Rinse the plant with lukewarm water, remove the mealybugs with a cotton bud soaked in diluted methylated spirit and raise the humidity of the room.

Leaves yellowing en masse almost always betray too much water and the start of root rot. Take out the root ball, cut away the soft, brown roots, and repot in fresh, well-draining substrate.

Propagation

The philodendron roots very easily from cuttings in spring or summer, like the pothos. Spot a node, that little bump from which a leaf and often an aerial root emerge, and cut the stem just below it, keeping one or two leaves.

Place the cutting in a glass of clear water, change the water each week, and wait for roots of a few centimetres to form before potting up in soil. You can also push several cuttings straight into the mother plant’s pot to thicken it. A cutting without a node will never make roots, it is the node that counts.

Toxicity

The whole plant contains calcium oxalate crystals. If chewed, a leaf causes strong irritation of the mouth and throat along with digestive upset. Keep the philodendron out of reach of cats, dogs and young children.

Month-by-month care calendar

Green Hub tips

• Pinch the stem tips in spring: the plant branches out and stays bushy instead of running into long bare stems.
• On a moss stake, the leaves grow larger; in a trailing basket, they stay smaller. The habit is yours to choose.
• To thicken a sparse pot, push a few cuttings straight into the mother plant’s pot.
• Leaf edges browning in winter: that is the dry air of heating. Mist or set the pot on damp clay pebbles.