The Ultimate Guide to Houseplant Soil

Choosing, Improving & Mixing the Perfect Blend

February 13, 2025

Why Soil is the Foundation of Healthy Houseplants

If you’ve ever struggled with droopy leaves, slow growth, or mysterious plant deaths, the problem might not be your watering schedule—it could be your soil. The right soil mix is the foundation of a thriving houseplant, influencing everything from root health to nutrient absorption.

At Scott’s Nursery, we carry Lambert’s pre-mixed potting soils, a high-quality starting point for your plants. But did you know that slight adjustments to your soil mix can maximize growth and longevity? Whether it’s adding aeration for oxygen-loving roots or improving drainage for succulents, fine-tuning your soil can make all the difference.

What You’ll Learn in This Guide:

Why soil is essential for healthy houseplants
How to optimize Lambert’s pre-mixed soils for different plant types
A DIY soil mix recipe guide for creating custom blends
The importance of repotting and soil health maintenance

By the end of this post, you’ll be equipped with scientifically backed soil knowledge to help your plants grow lush, vibrant, and strong.

Title

What Does Soil Do for Indoor Plants?

Soil is more than just dirt—it’s a living environment that provides everything a plant needs to grow. For indoor plants, where natural soil ecosystems don’t exist, the right potting mix must replicate nature as closely as possible. Here’s why soil is so crucial:

Water Retention & Drainage: Finding the Balance

Soil must hold enough water for roots to absorb without becoming waterlogged.
Too much water leads to root rot, while too little causes wilting and dehydration.
Well-draining soil contains air pockets that allow oxygen to reach roots, preventing suffocation.

Nutrient Supply: The Plant’s Food Source

Plants absorb essential nutrients (Nitrogen, Phosphorus, Potassium, Calcium, Magnesium) directly from the soil.
Over time, nutrients deplete, which is why repotting or fertilizing is necessary.
Some plants are “heavy feeders” (like Monsteras and Fiddle Leaf Figs), while others need fewer nutrients (like cacti).

Soil Structure: The Role of Organic vs. Inorganic Matter

Organic materials (peat, compost, bark) break down over time and provide slow-releasing nutrients.
Inorganic components (perlite, pumice, sand) improve aeration and prevent compaction.
Different plants need different balances of organic vs. inorganic matter.

Example:

Tropical foliage plants love rich organic soil with compost and peat moss.
Succulents & cacti thrive in gritty, inorganic soil with sand and perlite.

Quick Takeaway:

A good potting mix should:
Retain moisture without becoming soggy
Provide oxygen to roots
Contain nutrients or be fertilized regularly
Stay structurally stable and not compact over time

What Happens If You Don’t Refresh or Repot Your Soil?

Soil isn’t just a passive environment—it’s constantly changing. Over time, potting mix breaks down, depletes nutrients, and loses its structure, making it harder for your plants to thrive. If you’ve had a plant in the same pot for years and it’s stopped growing, the issue might not be the plant itself—it’s the soil!

Signs Your Plant Needs New Soil

Water sits on top of the soil and drains too slowly
Roots are growing out of the bottom of the pot (root-bound)
Soil looks compacted, crusty, or dusty
Yellowing leaves or stunted growth despite regular care
White crust (salt buildup) on top of the soil

Soil Compaction: The Hidden Killer

Over time, organic materials (like peat moss and compost) decompose and become denser. This reduces oxygen flow and makes it harder for roots to absorb water and nutrients.

The Fix:

Mix perlite, orchid bark, or pumice into your soil to keep it aerated.
Repot with fresh soil every 1-2 years for most plants.

Nutrient Depletion: When Soil Becomes "Empty"

Plants absorb nutrients from the soil, but if those nutrients aren’t replenished, the plant will start to struggle. Think of it like a diet—if you only ate the same food every day with no variety, you’d develop deficiencies!

The Fix:

Repot every 1-2 years OR regularly fertilize your soil.
Use organic amendments like worm castings or compost for a natural nutrient boost.

Salt Buildup: Why You Should Flush Your Soil

Over time, salts from fertilizers and tap water accumulate in the soil, which can burn plant roots and cause browning leaf tips.

The Fix:

Every few months, flush your soil by running water through the pot until it drains out the bottom.
Use filtered or distilled water if your tap water has high mineral content.

Root Binding: When Roots Outgrow Their Home

If roots don’t have space to grow, they become root-bound, wrapping tightly around the inside of the pot. This leads to stunted growth, water retention issues, and plant stress.

The Fix:

If roots are circling the pot, repot into a container 1-2 inches larger.
Trim any excess roots and loosen them gently before replanting.

Quick Takeaway:

Repot or refresh soil every 1-2 years to prevent compaction and nutrient loss.
Mix in aeration materials (like perlite) to extend soil life.
Flush your soil every few months to remove salt buildup.
Watch for signs of root crowding and repot if necessary.

Understanding Lambert’s Pre-Mixed Soils & How to Optimize Them

At Scott’s Nursery, we proudly carry Lambert’s professional-grade potting mixes, trusted by growers for their high-quality peat-based blends. These pre-mixed soils provide an excellent foundation for most houseplants, but depending on your plant’s needs, you may want to customize them for optimal growth.

What’s Inside Lambert’s Potting Mixes?

Lambert offers a variety of ready-to-use mixes, each designed for different plant types. Let’s break down their key ingredients:

Sphagnum Peat Moss – Retains moisture while allowing good airflow.
Perlite & Vermiculite – Enhances aeration and prevents compaction.
Limestone – Helps balance pH levels.
Organic Amendments (Compost, Bark, or Coco Coir) – Varies by mix to support root health.

How to Improve Lambert’s Mixes for Specific Plants

While Lambert’s soils work well right out of the bag, small tweaks can make them even better for different plant varieties. Here’s how:

For Foliage Plants (Monstera, Pothos, Philodendron, etc.)

Base Mix: Lambert All-Purpose Potting Mix
Enhancements: Add 20% orchid bark + 10% perlite
Why? Increases aeration and prevents soil from becoming too dense over time.

Foliage Plants

(Philodendron, Monstera, Pothos, etc.)

Base Mix: Lambert All-Purpose Potting Mix

Enhancements: Add 20% orchid bark + 10% perlite

Why? Increases aeration and prevents soil from becoming too dense over time.

For Ferns

(Boston Fern, Maidenhair Fern, etc.)

Base Mix: Lambert All-Purpose Mix
Enhancements: Add 20% peat moss + 10% vermiculite
Why? Holds moisture while maintaining proper airflow.

For Citrus & Fruit Trees

(Lemon, Fig, etc.)

Base Mix: Lambert All-Purpose Mix
Enhancements: Add 30% compost + 10% perlite

Why? Provides slow-releasing nutrients for long-term health.

For Succulents & Cacti

Base Mix: Lambert Cactus & Succulent Mix
Enhancements: Add 20% coarse sand + 10% pumice
Why? Ensures ultra-fast drainage and prevents root rot.

For Orchids

(Phalaenopsis, Dendrobium, etc.)

Base Mix: Lambert Orchid Mix
Enhancements: Add 30% extra bark + 10% charcoal
Why? Mimics the loose, airy environment orchids thrive in.

Quick Takeaway:

Lambert’s potting mixes provide an excellent starting point for most plants.
Small additions like bark, sand, or perlite can fine-tune the mix for specific plants.
Customizing your soil mix ensures your plants get the best balance of moisture, drainage, and nutrients.

DIY Soil Mix Guide: The Perfect Recipe for Every Plant Type

Whether you're looking to tweak Lambert’s potting mix or make your own from scratch, having the right balance of moisture retention, aeration, and nutrients is key. Below are scientifically backed soil mix recipes tailored to specific plant types.

Each recipe includes:
Base ingredients for structure and water retention

Aeration materials to prevent compaction
Add-ins for nutrients and drainage

Foliage Plants

(Philodendron, Monstera, Pothos, etc.)

50% All-Purpose Potting Mix
(or peat-based mix)
20% Orchid Bark
(improves aeration and structure)
20% Perlite

(prevents compaction and overwatering)

10% Worm Castings or Compost (slow-release organic nutrients)
Tip: Water when the top 2 inches of soil feel dry.

Succulents & Cacti

40% Cactus & Succulent Mix

(or sandy potting mix)
30% Coarse Sand

(ensures rapid drainage)
20% Pumice or Perlite

(aeration and prevents root rot)
10% Horticultural Charcoal (absorbs excess moisture)
Tip: Let soil dry completely before watering again.

Orchids

(Phalaenopsis, Dendrobium, Cattleya, etc.)

50% Orchid Bark Mix

(large particle bark keeps roots aerated)
30% Charcoal or Lava Rock (absorbs impurities and excess moisture)
10% Sphagnum Moss

(retains some moisture)
10% Perlite

(adds extra drainage)
Tip: Mist roots lightly between waterings for best results.

Ferns

(Boston Fern, Maidenhair Fern, etc.)

50% All-Purpose Mix

(moisture-retaining base)
30% Coconut Coir or Peat Moss (holds moisture while allowing airflow)
10% Vermiculite

(improves water retention)
10% Compost or Worm Castings (adds slow-releasing nutrients)
Tip: Keep soil consistently moist, but never soggy.

Citrus & Fruit Trees

(Lemon, Fig, Olive, etc.)

40% All-Purpose Mix

(rich in organic matter)
30% Compost or Aged Manure (supplies long-term nutrients)
20% Perlite or Sand

(enhances drainage)
10% Crushed Eggshells or Lime (provides calcium and maintains pH balance)
Tip: Keep soil slightly acidic (pH 6.0–6.5).

Quick Takeaway:

Customizing your soil mix helps plants thrive in their ideal environment.
Aeration materials (perlite, pumice, bark) prevent compaction.
Organic add-ins (worm castings, compost) provide essential nutrients.
Drainage materials (sand, charcoal, lava rock) prevent overwatering.

How to Check & Adjust Soil
pH for Indoor Plants

Most indoor gardeners focus on watering and light, but soil pH is just as important. The pH level of your soil affects how well your plants absorb nutrients, and even a slight imbalance can lead to poor growth.

What is Soil pH?

pH measures how acidic or alkaline the soil is, on a scale from 0 to 14:

Acidic soil: pH below 6.5
Neutral soil: pH 6.5–7.0
Alkaline soil: pH above 7.0

Most houseplants prefer slightly acidic to neutral soil (pH 5.5–7.0), but some plants thrive outside this range.

Ideal Soil pH Ranges for Different Houseplants

Foliage Plants → pH 5.5–6.5
Succulents & Cacti → pH 6.0–7.5
Orchids → pH 5.5–6.5

Ferns → pH 5.0–6.0
Citrus & Fruit Trees → pH 6.0–6.5

How to Test Soil pH

Soil pH Meter – Insert a digital pH meter into moist soil for an instant reading.
pH Test Strips – Mix soil with distilled water, dip the strip in, and compare colors.

DIY Vinegar & Baking Soda Test

Add vinegar to soil—if it fizzes, your soil is alkaline.
Add baking soda mixed with water—if it bubbles, your soil is acidic.

How to Adjust Soil pH

🔻 Lower pH

(Make Soil More Acidic)

Add peat moss (naturally acidic)
Mix in sulfur or aluminum sulfate
Water with acidic fertilizer (for azaleas, citrus, etc.)

🔺 Raise pH

(Make Soil More Alkaline)

Add dolomitic lime or crushed eggshells
Use wood ash (contains potassium and calcium)

Quick Takeaway:

Most houseplants prefer a pH between 5.5 and 7.0.
Testing soil pH ensures plants absorb nutrients properly.
Adjust pH using natural additives like peat moss (acidic) or lime (alkaline).

Practical Tips for Choosing the
Best Soil for Your Plants

With so many soil options available, it can be tricky to know whether to buy pre-mixed soil or create your own custom blend. The right choice depends on your plant type, maintenance preferences, and how much control you want over soil quality.

Should You Buy Pre-Mixed Soil or Make Your Own?

Buy Pre-Mixed Soil If:
You want a convenient, ready-to-use option.
You trust Lambert’s premium potting mixes as a solid foundation.
Your plants have general soil needs that don’t require extra customization.

Make Your Own Mix If:
You have specialized plants (e.g., rare aroids, orchids, or bonsai).

You enjoy fine-tuning aeration, water retention, and drainage.
You want to reuse old soil by refreshing it with new amendments.

Best of Both Worlds: Even if you buy potting soil, you can customize it by adding bark, perlite, or sand to better match your plant’s needs!

How to Store Soil & Keep It Fresh

Once you’ve chosen the right soil,
proper storage ensures it stays high quality:

DO NOT store soil in direct sunlight – UV rays break down organic matter.
Keep soil in a breathable container – Avoid mold by storing it in a ventilated bin or bag.
Check for pests before using old soil – Sterilize old soil by baking it at 180°F for 30 minutes.

The Role of Fertilizers & Soil Microbes

Even the best soil needs occasional fertilizing,
as nutrients don’t last forever.

Synthetic Fertilizers (Quick-Release)

Instant nutrients but require regular use.

Organic Fertilizers (Slow-Release)

Compost, worm castings, and aged manure enrich the soil over time.

Mycorrhizal Fungi & Beneficial Bacteria

Promote root health and help plants absorb nutrients more efficiently.

Pro Tip: When repotting, mix in a small amount of organic compost to give plants a slow-release nutrient boost!

Quick Takeaway:

Pre-mixed soils like Lambert’s are a great time-saving option.
DIY blends give more control over aeration, drainage, and moisture retention.
Store soil properly to prevent pests, mold, and breakdown.
Fertilizers & microbes help plants get the nutrients they need over time.

Helping Your Plants Thrive with the Right Soil

Now that you understand how soil affects your plants, you’re ready to make smarter soil choices—whether you’re using pre-mixed soils or fine-tuning a DIY blend.

At Scott’s Nursery, we’re happy to help you find the perfect soil for your plants and recommend repotting supplies, soil amendments, and fertilizers to keep your indoor garden thriving!

Check out our selection of Lambert’s potting soils & plant care products in-store or online!

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The Ultimate Guide to Houseplant Soil

Choosing, Improving & Mixing the Perfect Blend

What Does Soil Do for Indoor Plants?

What Happens If You Don’t Refresh or Repot Your Soil?

Understanding Lambert’s Pre-Mixed Soils & How to Optimize Them

DIY Soil Mix Guide: The Perfect Recipe for Every Plant Type

How to Check & Adjust Soil
pH for Indoor Plants

Practical Tips for Choosing the
Best Soil for Your Plants

Subscribe

Trending Articles

Top Ten Easiest Houseplants

Understanding Yellowing Leaves in Houseplants

Related Products

Sphagnum Moss Quebec

Lambert Seed and Cutting Mix

Lambert Perlite 8.8L

Gaia Green Greensand

Lambert Cactus and Succulent Mix 4.4L

Lambert Vermiculite 8.8L

Gaia Green Soluble Seaweed Extract

Lambert Potting Mix

Lambert African Violet Mix

Gaia Green Rock Phosphate

Lambert Organic Potting Mix 44L

Lambert Horticultural Wood Charcoal 4.4L

Gaia Green Rock Dust Blend 2 kg

Gaia Green Oyster Shell Flour

Lambert Organic Flower and Vegetable Soil 44L

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Lambert Peat Moss

The Ultimate Guide to Houseplant Soil

Choosing, Improving & Mixing the Perfect Blend

What Does Soil Do for Indoor Plants?

What Happens If You Don’t Refresh or Repot Your Soil?

Understanding Lambert’s Pre-Mixed Soils & How to Optimize Them

DIY Soil Mix Guide: The Perfect Recipe for Every Plant Type

How to Check & Adjust Soil pH for Indoor Plants

Practical Tips for Choosing the Best Soil for Your Plants

Subscribe

Trending Articles

Top Ten Easiest Houseplants

Understanding Yellowing Leaves in Houseplants

Related Products

Sphagnum Moss Quebec

Lambert Seed and Cutting Mix

Lambert Perlite 8.8L

Gaia Green Greensand

Lambert Cactus and Succulent Mix 4.4L

Lambert Vermiculite 8.8L

Gaia Green Soluble Seaweed Extract

Lambert Potting Mix

Lambert African Violet Mix

Gaia Green Rock Phosphate

Lambert Organic Potting Mix 44L

Lambert Horticultural Wood Charcoal 4.4L

Gaia Green Rock Dust Blend 2 kg

Gaia Green Oyster Shell Flour

Lambert Organic Flower and Vegetable Soil 44L

Worm Castings Growing Green

Lambert Peat Moss

How to Check & Adjust Soil
pH for Indoor Plants

Practical Tips for Choosing the
Best Soil for Your Plants