English ivy

English ivy grows across Europe and western Asia, climbing tree trunks and walls with small clinging roots and carpeting the ground in shade where little else will. It has been an indoor plant for as long as there have been indoor plants, and it is the one on this list that most wants to be outside. A cool bright room suits it; a warm dry one gives it spider mites within a month. Understanding that it is a temperate plant, not a tropical one, solves nearly everything about it.

Light

Indoors, bright indirect light keeps a variegated ivy marked and a plain green one growing well. Green forms take a noticeably dimmer spot and are the better choice for a shaded shelf. On a variegated plant, cut out any shoot that comes back plain green, because it grows faster than the marked growth and will take the whole plant over in a season.

Outdoors it grows in shade to part shade and dislikes hot dry sun on its leaves.

Water and warmth

Water when the top 2 to 3 cm of compost is dry, which is about every six days in summer and every twelve in winter. Keep it lightly moist rather than wet, and let it drain.

Temperature matters more than most people expect. Ivy is happiest between about 10 and 20 degrees and tolerates a good deal less. A cool bright hallway, a porch or an unheated bedroom suits it far better than a living room at 22 degrees with the radiator on. The plant sheds leaves, browns at the edges and fills with spider mites in dry warmth, and every one of those problems eases when it is moved somewhere cooler.

Feeding and repotting

Feed at half strength monthly from spring to early autumn and stop in winter. Repot in spring, one size up. To keep a plant the same size indefinitely, take it out, trim a third off the root ball and return it to the same pot with fresh compost, which it takes without complaint.

Pruning and propagation

Cut it back as hard as you like, in spring or at any point in the growing season. It breaks new growth readily from old wood, and a plant that has gone long and bare recovers into something dense within a couple of months.

Cuttings root very easily. Take a stem with three or four leaves, cut just below a node, and stand it in water or push it into damp compost; roots appear within two to three weeks. Outdoors, a trailing stem pegged onto the soil roots at every node it touches, which is also how it spreads where it is not wanted.

Growing it outside

In a temperate garden ivy is useful in the places nothing else will grow: dry shade under trees, north facing walls, steep banks. It is valuable to wildlife, flowering in autumn when little else does and fruiting in late winter.

It is also invasive in several countries, notably in parts of North America and Australia, where it smothers ground flora and weighs down trees. Check the position where you live before planting it out, and keep it in a pot if there is any doubt.

Ailments

Spider mites are the defining problem of indoor ivy and they are a symptom of warm dry air rather than bad luck. Crisp brown edges have the same cause. A variegated plant going green needs more light. Yellow leaves need a finger in the compost before a diagnosis, because both a drowned plant and a plant that dried out completely shed them. The ledger below has the rest.