Blue candle

Blue candle: how do you recognise it?

Habit

Columnar or candelabra-shaped cactus, about 1 m tall and 60 cm across indoors, with side branches; several metres tall in the wild.

Stem

Blue-green with a waxy bloom and five or six ribs; about 6–10 cm thick.

Spines

Small spine cushions on the ribs with short black spines; young plants have few and short ones.

Flower

Small cream-white to greenish flowers about 3 cm across, rare indoors and only on older plants.

Fruit

Small, round, purple berries about 1–2 cm across that look like bilberries; they are eaten in Mexico.

Plants: March–April · Pruning: April–May

Why grow it?

• A striking blue-green column that looks good all year round, even without flowers.
• Fairly fast-growing for a cactus and soon becomes a sturdy, sculptural plant.
• Very little work: little water, no strict pruning and hardly any feeding.
• Easy to propagate from stem cuttings of broken or shortened branches.
• Suits a modern or tropical-looking living room and goes well with green and grey foliage.

Blue candle: where does it grow best?

• Full sun, for example on a south- or west-facing windowsill. In summer it may go outdoors, under cover and sheltered from rain.
• Very free-draining, mineral mix: cactus compost half and half with coarse sand, fine grit or pumice; neutral.
• Dry: let the soil dry out completely between waterings and never let water stand in the saucer.
• Put it in a sturdy, deep pot in a permanent spot with room for the side branches; a heavy pot stops it toppling over.

Light

Sunny

Potting soil

Cactus compost

Acidity

Neutral

Watering

Sparingly

Size

1 m tall, 0.6 m wide

Temperature

Minimum 10 °C

Goes well with

• Prickly pear: A flat cactus with rounded pads that contrasts with the straight column.
• Agave: A sturdy grey-blue rosette that goes well with the blue-green.
• Aloe: Fleshy, calm foliage for the same sunny, dry spot.
• Echeveria: A low rosette in blue-grey tones at the foot of the column.

Blue candle: when and how to plant it?

Plant in March–April.

1. Repot in March–April, at the start of growth, or as soon as the plant fills its pot; usually every 2–3 years.
2. Wear thick gloves or hold the plant with folded newspaper or foam; the spines prick.
3. Choose a sturdy, deep pot with a drainage hole, one size up from the old one; terracotta dries out faster than plastic.
4. Fill with a mix of cactus compost and coarse sand or grit, set the plant at the same depth as before and firm lightly.
5. Do not water for about a week after repotting so that damaged roots can heal.

Care

Water

From April to September water when the soil is completely dry, roughly every 1–2 weeks depending on the heat; let the excess drain away. In winter little or none.

Feeding

From May to August, once a month, give cactus feed at the recommended dose or slightly weaker. Not in winter.

Light

Plenty of sun. After winter, get it used to strong sunlight gradually, or it will get yellow or brown sunburnt patches.

Turning

Give the pot a quarter turn now and then so that the plant grows straight and evenly instead of leaning towards the light.

Repotting

Every 2–3 years in spring, in fresh, mineral mix in a sturdy pot.

Tip: It grows fairly quickly: give it a heavy, deep pot, full sun and, in winter, a dry, bright spot above 10 °C, and it will stay free of spots.

Blue candle: when to prune it?

Pruning months: April–May.

When: It is not really pruned. In April–May you can shorten a plant that is too tall or leaning, and you get cuttings at the same time.

How:

• Cut through a branch or the trunk at the height you want with a clean, sharp saw or knife, wearing thick gloves and using folded newspaper.
• Let the wound on the plant dry in the open air for a few days; new side branches often form below the cut.
• Cut away rotten or shrivelled parts back to healthy, green tissue.
• Use the cut pieces as cuttings; see propagation.

Caution: It has spines and is heavy and awkward to cut: wear thick gloves and protect your eyes.

Pruning: when and how · Pruning calendar and basic rules

Propagation

Cuttings

In spring or summer cut off a branch with a clean knife and let it dry for 1–2 weeks until the wound has formed a skin. Stand it upright in a dry, sandy mix and give a small drop of water only after 3–4 weeks, when it has rooted.

Seed

In spring sow on a sandy mix, barely covering the seed, under clear film at 20–25 °C in a bright place. The seedlings grow slowly.

Blue candle: how does it get through the winter?

• Not hardy in Belgium: keep it above 10 °C. The best winter spot is bright and cool, at 10–15 °C.
• Keep the soil dry or almost dry from October to March; cold plus wet causes rot and spots.
• Do not leave it in a cold draught or against a cold window, or directly above a radiator: dry, hot air invites scale insects.

Diseases and pests

• Spots: Yellow, brown or corky patches on the stem after cold, damp spells, especially in winter. Keep it dry and above 10 °C; the patches do not go away, but new growth stays healthy.
• Rot: Soft, brown or dark stem base from too much water or watering in the cold. Stop watering, cut away rotten parts back to healthy tissue and root a healthy piece as a cutting.
• Stretching: A thin, pale, elongated top means too little light. Move it to a sunnier spot; you can shorten the stretched part.
• Mealybug and scale: White, cottony tufts or brown scales between the ribs and near the spines. Remove them with a soft brush or cotton bud and repeat after a week.
• Sunburn: Yellow or brown dried-out patches after sudden strong sun, for example after winter. Get it used to the sun gradually.

Through the year

• January: Rest: dry, bright, 10–15 °C. No water.
• February: Rest: dry and bright. No water.
• March: Repotting possible. Gradually get it used to more sun.
• April: Repot or shorten. Start watering when the soil is dry.
• May: Water when the soil is dry. Start feeding. Take cuttings.
• June: Water when the soil is dry and feed. Plenty of sun and fresh air.
• July: Water when the soil is dry and feed.
• August: Water when the soil is dry. Last feed.
• September: Last watering when the soil is dry. No more feeding.
• October: Bring indoors before it turns cold. Almost stop watering.
• November: Rest: dry and bright, above 10 °C.
• December: Rest: dry and bright, above 10 °C.

Did you know?

• The name Myrtillocactus refers to the Latin myrtillus (little myrtle or bilberry) and alludes to its bilberry-like fruits.
• In Mexico the fruits are called garambullos and are eaten and sold there.
• The blue waxy bloom on the stem protects the plant from too much sun and from drying out.