Succulent Soil Mixing Guide — Components & Optimal Ratios

# Selecting Soil for Succulents: A Complete Guide to Soil Composition and Mixing Ratios

The choice of soil is one of the most important factors in cultivating succulents. Since succulents are sensitive to excessive moisture, regular potting soil for herbaceous plants offers poor drainage and easily leads to root rot. This article explains the types of soil best suited for succulents and the ideal mixing ratios.

Soil Conditions Suited for Succulents

There are three major requirements for succulent soil composition.

High drainage Succulents store water in their leaves and stems, so roots easily rot if kept constantly moist. The ideal soil mix drains water quickly after watering and dries appropriately.

Good air circulation Roots need to breathe. Without air passages in the soil, oxygen deficiency weakens roots and encourages the growth of anaerobic pathogens. Using granular soil creates air passages between the particles.

Moderate water retention Prioritizing only drainage causes water to drain too quickly, leaving roots insufficient time to absorb moisture. Especially in summer when drying is rapid, the soil needs some moisture-retaining components. Balancing drainage and water retention is essential.

Major Soil Types and Their Characteristics

Here are the typical soils used in succulent soil mixes.

Red volcanic soil (small grain) Made from granulated Kanto loam, this is the basic material for succulent soil. It combines moderate water retention and drainage, with a pH around 6.0 (slightly acidic). Particles break down over time, reducing drainage, so repotting every 1-2 years is ideal. Hard red volcanic soil resists breakdown and lasts longer, though it's somewhat pricier.

Kanuma soil (small grain) A pumice-like soil from the Kanuma region of Tochigi Prefecture. It offers higher drainage than red volcanic soil and excellent air circulation. With a pH around 5.0 (acidic), it suits species that prefer acidity. Its yellowish color turns whitish when dry, making it easy to judge watering timing by sight.

Perlite A white pumice-like material made by heating perlite at high temperatures. Excellent drainage and air circulation with very lightweight properties. It's mixed in to lighten overall soil or improve drainage. With almost no water retention, using too much causes excessive drying.

Pumice (Hyuga soil) Natural pumice with excellent drainage and air circulation. Particles resist breakdown and last long-term. When used alone, it lacks water retention, so it's mixed with red volcanic soil. Also used as drainage material at pot bottoms.

Vermiculite A golden, flaky material made from heated mica. Excellent water retention and nutrient-holding capacity with lightweight properties. Succulent soil may sometimes have too much water retention, but mixing in small amounts improves nutrient retention.

Charred rice husks Made from carbonized rice husks. Improves air circulation, provides sterilization, and adjusts pH (alkaline). Mixing 5-10% of the total soil improves soil quality.

Basic Mixing Ratios

Here are versatile mixing ratios suitable for most succulents.

Basic mix (All-purpose) Red volcanic soil (small grain) 4 : Kanuma soil (small grain) 3 : Perlite 2 : Charred rice husks 1

This mix balances drainage and water retention well, suitable for general succulents including Echeveria, Sedum, Graptopetalum, and Pachyphytum.

Drainage-focused (for drought-preferring species) Red volcanic soil (small grain) 3 : Pumice (small grain) 3 : Kanuma soil (small grain) 2 : Perlite 2

This mix suits species especially sensitive to excess moisture, like cacti, Agave, and hard-leafed Haworthia. The fast drying after watering also prevents summer rot.

Slightly higher water retention (growth-focused) Red volcanic soil (small grain) 5 : Kanuma soil (small grain) 2 : Vermiculite 2 : Charred rice husks 1

Suitable for species requiring adequate moisture during growth, or small pots that dry too quickly. However, winter management requires care, needing adjustments to reduce watering frequency.

Ratio Adjustments by Species

Succulents prefer different soils depending on genus and species. Here are adjustment tips for representative varieties.

• Echeveria: Basic mix works fine. Slightly higher drainage is reassuring
• Haworthia: More red volcanic soil for slightly higher water retention. Since these are grown avoiding direct sun and dry slowly, ensuring drainage is important
• Sedum: Basic mix is sufficient. Sedum is hardy and not particular about soil
• Lithops: Prioritize drainage. Use a mix heavy in pumice, with pumice also as decorative surface dressing
• Caudex types: Drainage-focused. Mix heavily with large pumice pieces for a loose, granular composition

Adjustments by Season and Environment

Even the same mix dries at different rates depending on growing conditions.

• Balcony cultivation in windy areas: Faster drying, so slightly increase water retention
• Indoor cultivation with poor air circulation: Slower drying, so increase drainage
• Rainy season and summer: Drainage-focused mixes are safer to prevent rot from humidity
• Small pots (2-3 inches): Low soil volume with fast drying, so slightly increase water retention
• Large pots (5 inches or larger): Core stays moist, so increase drainage

Commercially Available Succulent Soil

Packaged "succulent and cactus soil" sold at garden shops and home centers is convenient but varies in quality between manufacturers. Some products lack sufficient drainage, so before purchasing, check the packaging for composition and consider adding perlite or pumice to improve drainage as needed.

Get Succulent and Soil Advice at Brî Choku

At Brî Choku, breeders can advise on soil mixes suited to your succulent varieties. Breeders often share the compositions they actually use, providing practical information tailored to your growing environment. Consider consulting about soil when purchasing succulents.