Myrtillocactus Care

Myrtillocactus Care in Phoenix

(Blue Myrtle and Crested Forms)

Overview

Myrtillocactus, commonly known as Blue Myrtle, is a drought-tolerant desert cactus known for its blue-green coloration and architectural shape. Crested forms develop sculptural, fan-like growth patterns that make each plant unique. These care instructions are written specifically for indoor growing conditions in the Phoenix metro area, where strong light and low humidity support healthy growth.

Light

Indoors:
• Requires bright, direct light for several hours each day.
• Best placed in a south or west-facing window.
• Stretched, pale, or leaning growth indicates the plant needs more sun.

Outdoors in Arizona:
• Prefers morning sun with afternoon shade.
• Newly purchased or crested plants should be protected from intense midsummer light.

Water

Allow the soil to dry out completely before watering again.

Indoor watering schedule for Phoenix:
• Spring/Summer: Every 2–3 weeks.
• Fall/Winter: Every 4–6 weeks.

Notes:
• Water thoroughly until it drains through the pot.
• Do not leave the plant sitting in standing water.
• Wrinkling at the base signals the plant is ready for water.
• Softening or darkening of tissue suggests overwatering.

Soil and Potting

• Use a fast-draining cactus or succulent mix.
• Amend with pumice or perlite to improve drainage.
• Terracotta pots are recommended for airflow and faster drying.

Temperature and Environment

• Ideal temperature range is 60–90°F.
• Protect from frost and avoid temperatures below 40°F.
• Low humidity is preferred and reduces risk of rot.

Growth Habit

• Standard forms grow upright and branch with age.
• Crested forms grow in slow, wavelike fans that create a sculptural look.
• Blue coloration becomes more pronounced with strong, consistent light.

Fertilizing

• Fertilize once monthly from March through September with a diluted cactus fertilizer.
• Do not fertilize in winter.

Common Issues

Overwatering:
• Mushy spots, darkened tissue, or a soft base.
• Reduce watering and allow soil to fully dry.

Underwatering:
• Noticeable wrinkling or slight deflation.
• Resume normal watering schedule.

Sun Stress:
• Pale or brown areas may appear if exposed to sudden intense sun.
• Gradually acclimate if moving outdoors.

Pests:
• Mealybugs or scale may appear on crested ridges.
• Treat with isopropyl alcohol swabs or neem oil.

Repotting

• Repot every 2–3 years or when roots become crowded.
• Size up only 1–2 inches in diameter.
• Best repotting period is spring.