Compost is sometimes called “black gold” because it helps gardens grow. If you make your own compost, it’s free gold. But there are some basic rules you need to follow before you start spreading compost in your yard. Plants can also be hurt by using compost too early, too much, or at the wrong time.
As an avid indoor gardener, I’m always looking for ways to keep my potted plants healthy and thriving. Compost provides an excellent nutritional boost for container plants by improving soil structure and providing a slow release of nutrients. Follow these simple tips to properly amend your potting mixes with compost to get the most out of this “black gold” with your indoor plants.
Choosing the Right Compost
Not all composts are created equal when it comes to potted plants Here are some important factors to consider
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Maturity – Mature compost has fully broken down and stabilizes nutrients, Immature compost can harm plant roots and tie up nutrients
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Nutrient levels – Compost high in nutrients like nitrogen can burn delicate plant roots. Opt for compost with moderate nutrient levels.
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Salts – Excessive salts from poor composting can damage plants Test electrical conductivity to ensure suitable salinity,
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Contaminants – Compost should not contain visible trash, plastic, glass, or metals. These can inhibit plant growth.
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Organic seal – Look for compost certified organic by organizations like the US Composting Council. This ensures quality standards.
High-quality, organic-approved compost provides the ideal nutritional supplementation for container plants without the risks of contaminants, imbalances, or phytotoxic compounds.
How Much Compost to Use in Potting Mix
I recommend using compost to make up 25-50% of your overall potting soil volume. A general guideline is:
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Houseplants – 25% compost, 75% potting mix
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Vegetables & herbs – 30% compost, 70% potting mix
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Flowers & shrubs – 40-50% compost, 50-60% potting mix
Start with lower ratios if you’re uncertain of your compost’s exact nutritional content. Too much compost can potentially burn plant roots with an overload of nutrients. Mix your compost with sterile potting mixes free of pathogens.
Incorporating Compost into Newly Potted Plants
When potting new plants, blend compost directly into the soil mix before filling containers. Follow these steps:
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Choose containers with drainage holes to prevent soggy soil.
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Mix compost with sterile potting mix in suitable ratios.
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Moisten the blend and fill pots about 3/4 full.
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Remove plants from old containers and loosen bound roots.
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Place plants in pots and fill remaining space with mix.
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Water thoroughly until water drains from bottoms.
Ensure the compost blend remains loose to allow air circulation to roots. Pack gently around plants to stabilize. Compost integrated directly into soil gives plants immediate access to nutrients for vigorous new growth.
Top-Dressing Established Container Plants
To revitalize established potted plants, apply fresh compost as a nutritious top-dressing mulch:
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Remove any top layer of depleted soil or mulch.
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Spread 1-2 inches of compost over the exposed soil surface.
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Work gently into the top 1-2 inches of existing soil.
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Water thoroughly after top-dressing.
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Repeat every 3-4 months as needed.
Top-dressing with compost replenishes nutrients and organic matter in containers over time. It also helps retain moisture while allowing good gas exchange for healthy roots.
Side-Dressing Root Zones
An easy way to nourish established plants is side-dressing around the root zone perimeter:
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Determine how far plant root systems extend in pots.
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Clear back surrounding soil to expose outer root area.
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Mound fresh compost around visible root zone.
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Fill back in gaps with surrounding soil.
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Water well to settle amendments.
Side-dressing targets nutrition precisely where roots are most active and in need. It disturbances the plant less than top-dressing the entire surface. Repeat every 2-3 months for continual benefits.
Making Compost Tea
Compost tea is a nutritious plant tonic that harnesses the benefits of compost in liquid form. Follow these steps:
Brewing
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Fill a 5-gallon bucket halfway with quality compost.
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Add water until 3/4 full and mix vigorously.
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Let steep 3-7 days, stirring daily and keeping water oxygenated.
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Strain out solids and store tea in cooled jugs.
Applying
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Dilute compost tea at a 5:1 ratio with water.
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For houseplants, use as a soil drench every 2-4 weeks.
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For gardens, spray foliage or soil as a fertilizer booster.
The live microbiology in compost tea enhances nutrient uptake, disease resistance, and overall vigor for container plants.
Troubleshooting Compost Issues
When amending with compost, a few issues can arise:
Problem: Fungus gnats
Solution: Use only properly cured compost to avoid larvae. Add sand top-dressing to dry out top layers.
Problem: Mold growth
Solution: Allow containers to dry adequately between waterings for good drainage and aeration.
Problem: Nutrient burn
Solution: Leach excess salts by pouring water through soil. Re-pot with a milder mix if severe.
Problem: Leggy or stunted growth
Solution: Adjust compost ratios to provide better nutrient balance.
Monitor your plants closely when first using new compost sources to detect any problems promptly. Adjust application rates and moisture levels accordingly.
5 Indoor Plants That Thrive With Added Compost
If properly mixed into potting soil or applied as mulch, compost provides a nourishing boost to all container plants. However, some indoor varieties respond particularly well to this organic amendment. Here are 5 great candidates for compost-enhanced potting mixes:
1. Spider Plant
Fast-growing spider plants become even more vigorous and prolific when grown in nutrient-rich compost mixes. More baby plantlets will sprout when given ideal nutrition.
2. Chinese Evergreen
These low-light beauties develop glossier foliage with more pronounced variegation when supplemented with compost. Steady fertilization prevents chin evergreens from becoming leggy.
3. Peace Lily
Peace lilies flower more prolifically when their heavy root systems have access to compost-amended soil. They are heavy feeders that flourish with compost.
4. Orchids
Top-dress container orchids with compost to stimulate lush foliage and abundant blooming. The open, organic structure also prevents soggy soil.
5. Flowering Annuals
Marigolds, petunias, geraniums and other flowering plants stay stockier and bloom continuously when grown in nutrient-rich compost mixes.
The next time your indoor plants need re-potting or a nutritional boost, reach for the compost bag instead of synthetic fertilizers! Your plants will thank you for the organic TLC.
As a Fertilizer
Some nutrients are added to the soil by compost, but it is usually not enough to be the only fertilizer. The right amount of commercial fertilizer needs to be used at the right time for plants that need certain nutrients, like lawns (nitrogen) and vegetables and other crops (nitrogen, phosphorus, potassium, plus a range of micronutrients).
The nutrient content of compost, unlike commercial fertilizer, organic or other, is unpredictable. A thin layer of mature compost spread over your lawn or in your vegetable garden is always a good idea, but it shouldn’t be the only thing that feeds your plants.
4 Ways to Use Compost in Your Garden
Mixing organic matter into any kind of soil is good for it, and compost is a great way to do that. Organic matter is key for soil productivity, it improves the soil texture, microorganism activity, and nutrient uptake. Even rich, good-quality loamy soil gets compacted over time and adding organic matter loosens up the soil. Large soil particles in sandy soil don’t hold water and nutrients very well. Adding organic matter to sandy soil makes it better at holding water so that it doesn’t drain faster than plants can absorb it. Clay soil with is dense soil particles sticks together, which leads to poor drainage and insufficient oxygen. Adding organic matter to heavy clay soil loosens it up and improves aeration.
It is better for the soil to hold important nutrients like calcium, magnesium, and potassium when organic matter like compost is added to it. The acids in organic matter help plant roots take in water and nutrients. They also dissolve soil minerals so that plant roots can use them. By adding compost to soil, you also keep the pH stable, which is important because plants can’t get or use nutrients properly if the pH is off.
As important as compost is, it is only used in small amounts and over time, about once a year. This is because only 3 to 6 percent of soil is organic matter. Two to three inches of mulch should be spread over the soil, and it should be worked in with a tiller, shovel, or garden fork.
How to Add Compost in the Garden
Can you put compost on top of a plant?
You can avoid disturbing the soil and adding an inch of compost on top of the soil itself. When you water the plant, the nutrients from the compost will leach into the soil. If you have little compost, you can add it near the base of the plant rather than cover the entire potting soil. Just keep some space, so the compost does not touch the plant.
Can you add compost to potting soil?
Compost is a fantastic addition to potting soil. However, it’s best to use compost as an amendment to potting soil rather than using it alone. A good rule of thumb is to mix equal parts compost and potting soil for a nutrient-rich, well-draining mix. Q: How Often Should I Turn My Compost Pile?
Should I cover potting soil with compost?
When you water the plant, the nutrients from the compost will leach into the soil. If you have little compost, you can add it near the base of the plant rather than cover the entire potting soil. Just keep some space, so the compost does not touch the plant. I recommend that you cover the layer of compost with mulch.
How do you mix potting soil & compost?
Pour the potting soil on this surface based on how much you need for your container plants. Then add 25% to 50% of compost to the potting soil and mix it well. Please keep adding a little water when you’re preparing this potting soil and compost mixture. You want it to be moist but not soggy.