Indoor vs Outdoor Potting Soil: 4 Key Differences To Remember
Looking for a detailed overview of indoor vs outdoor potting soil?
Knowing how indoor and outdoor potting soils differ can help gardeners, especially beginners, determine which soil meets your plants’ needs.
In this article, we’ll explore four key differences in indoor vs outdoor potting soil and answer three FAQs about their use.
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Indoor vs Outdoor Potting Soil: 4 Key Differences
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Indoor Potting Soil |
Outdoor Potting Soil |
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May contain biochar, peat moss, perlite, and coco coir |
May contain peat moss, pine bark, compost, and fertilizer |
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Light with good drainage and aeration |
Coarse with good moisture retention and aeration. |
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Indoor container gardening |
Outdoor potted plants and landscaping |
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Available as organic potting soil, seed starting mix, succulent soil mix, and more |
Available as all purpose potting mix, raised or garden bed potting soil, and garden potting soil |
Here’s a detailed comparison of these two potting soils:
1. Ingredients
The composition of these potting soils is slightly different.
A. Indoor Potting Soil
Indoor potting soil may contain peat moss, coco coir, biochar, perlite, pumice, and other ingredients.
While it may or may not be soilless, it mostly won’t contain organic matter like pine bark which could shelter pests like fungus gnat larvae. Usually, conventional indoor soils are also low in plant food and need fertilizer as per plant requirements.
B. Outdoor Potting Soil
Outdoor potting soil contains most of the same indoor soil ingredients, except it’s rich in fertilizer like earthworm castings and alfalfa meal.
It also has ingredients for greater moisture retention, like biochar, peat moss, and vermiculite.
Note: Avoid potting soils containing peat moss (decomposed sphagnum moss), vermiculite, perlite, and coconut coir as these ingredients have heavy carbon footprints.
2. Characteristics
Here’s how indoor and outdoor potting soil differ in characteristics:
A. Indoor Potting Soil
Indoor potting mix or potting soil is light and fluffy, offering a balance between moisture retention and water drainage. The soil also has good air circulation to facilitate the growth of plant roots.
Moreover, its excellent aeration and drainage characteristics help prevent root rot from overwatering an indoor plant.
Read about how potting mix and potting soil differ from each other.
B. Outdoor Potting Soil
Outdoor potting soil is coarse and heavy, with large particles that resist compaction while helping plants stay anchored even in harsh conditions.
It offers superior moisture and nutrient retention than your typical indoor soil mix.
3. Applications
Here are the different ways to use indoor and outdoor potting soil:
A. Indoor Potting Soil
You can use indoor potting soil for all kinds of container gardening — for a small container plant, a large indoor potted plant, or even a herb garden.
It’s usually available as sterile potting soil (doesn’t have plant pathogens or microbes), but some potting mixes have beneficial microbes that boost plant growth.
Regardless of that, an indoor soil mix is a more controlled medium than an outdoor mix. But you should replace or refresh the soil every 12 to 18 months as potting soil can lose value over time.
B. Outdoor Potting Soil
You can use outdoor potting soil for:
- Raised beds.
- Outdoor container gardening.
- Landscaping.
It’s a better medium for growing plants outdoors than your standard garden soil or outdoor soil.
However, this potting soil is prone to fungal growth and fast organic material decomposition due to external conditions like higher temperatures, moisture, and microbe content. So, you’ll have to repot your plants annually.
4. Soil Types
Here are the different categories of potting soil for indoor and outdoor use:
A. Indoor Potting Soil
The common types of potting soil for indoor use include:
- Organic Potting Soil: A houseplant soil made from Organic Materials Review Institute (OMRI) certified ingredients, like worm castings, alfalfa meal, and compost.
- Seed Starting Mix: A light soilless mix with low nutrition for seed germination.
- Orchid Potting Mix: A slightly acidic potting soil mix containing fir bark.
- Cacti and Succulent Soil Mix: A fast-draining soil specifically designed for succulents.
- African Violet Potting Mix: A slightly acidic soil with good drainage.
- All Purpose Potting Soil: A general-purpose soil with a suitable soil structure and nutrient composition for different plants.
Looking for a high-quality indoor potting soil that meets various plant needs?
Meet Rosy.
The Best Potting Soil for Houseplants: Rosy Soil’s Indoor Potting Mix
Rosy Soil’s Indoor Potting Mix is an all-natural growing medium that supports any houseplant, like philodendrons, pothos, succulents, and ferns.
Instead of peat moss and other unsustainable amendments, Rosy’s soil mix contains carbon-negative biochar, vegan compost (aged compost), and root-boosting mycorrhizal fungi. It helps support plant growth by conserving water, improving drainage, and delivering nutritious plant food.
What’s more?
The soil has a negative carbon footprint — it literally captures atmospheric carbon dioxide! So, it’s the best potting soil for a healthy indoor garden and our planet.
B. Outdoor Potting Soil
You can use these soils for outdoor gardening:
- All Purpose Potting Soil: A type of soil available as in-ground and container soil.
- Raised Bed Potting Soil: A soil mix with nutrient-rich ingredients formulated for fruits and vegetables.
- Garden Potting Soil: An in-ground (non-container) soil mix made to increase plant yield. It’s a better medium than standard garden soil.
Note: You can use all purpose potting soil for indoor or outdoor gardening. It’s viable for different types of plants and can be useful when shifting indoor plants into an outdoor environment.
3 FAQs About Indoor and Outdoor Potting Soil
Here are the answers to some potting soil questions:
1. Can You Use Indoor Potting Soil as a Substitute for Outdoor Potting Soil?
Yes, you can use indoor potting soil for an outdoor plant, but you shouldn’t use outdoor potting soil for an indoor plant.
Here’s why:
- Indoor potting soil has a viable structure for outdoor plants. You just need to add fertilizer and a wetting agent since indoor soil typically dries quickly.
- Conversely, outdoor potting soil may have excess nutrients and organic matter that attracts pests like fungus gnat larvae. Plus, it’s heavy and has high water retention, which can cause root rot in an indoor plant.
Alternatively, you could use all purpose potting soil since it’s beneficial for houseplants and outdoor plants.
2. Can You Use Topsoil or Gardening Soil Instead of Outdoor Potting Soil?
No, topsoil and gardening soil are too heavy and dense to be used as growing media for outdoor plants.
They are native soil that doesn’t offer a viable soil structure for growing plants. Their density will reduce airflow and make it hard for plant roots to access water.
Moreover, being natural soil, they don’t necessarily contain the right nutrient composition to sustain plant growth. They can also contain pests like weed seeds and insects.
3. How Do You Choose The Best Indoor Potting Soil for Your Houseplant?
Each type of potting soil has different benefits. So, it’s best to choose an indoor potting soil as per the needs of your houseplant.
But aside from the type, here are a few tips for selecting the best indoor soil:
- Look for a soilless mix to avoid easy compaction.
- Avoid unsustainable ingredients like sphagnum peat moss, coco coir, and perlite. Instead, select ingredients that are eco-friendly, like biochar and compost.
- Choose an organic potting mix over soils with synthetic ingredients since they can affect the soil and plants’ health.
Wrapping Up
Selecting the right type of soil for growing plants is as important as selecting a spot with suitable growing conditions.
Use the information we covered here to determine what soil type your plant really needs.
If you’re looking for indoor potting soil, you should try Rosy Soil’s Indoor Potting Mix.
It’s the perfect blend to give your indoor garden a green boost!