Compost is a nutritional powerhouse for plants and soils It contains a diverse array of organic matter, nutrients, and beneficial microbes. With all these properties, it may seem like compost would be an ideal medium for starting seeds. However, using compost for seed starting is somewhat controversial.
Some gardeners swear by planting seeds directly in compost with great success. Others warn against it due to potential risks. So what’s the real scoop on starting seeds in compost? Here we’ll examine the pros and cons so you can make an informed decision.
The Potential Benefits of Starting Seeds in Compost
There are some clear advantages to using compost as a seed starting medium
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Nutrients: Compost contains nitrogen, phosphorus, potassium and many other nutrients essential for seed germination and growth. This means compost can often provide all the fertilizer needs of young seedlings.
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Organic matter: The organic matter in compost helps retain moisture while still allowing good drainage and air circulation for roots.
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Biological activity: Compost contains beneficial microbes that may help suppress soil-borne diseases and aid plant growth.
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Cost savings: Homemade compost is free compared to buying commercial seed starting mixes.
With perks like these, it’s easy to see the appeal of planting seeds in straight compost. However, there are also some potential drawbacks to consider.
Risks of Starting Seeds in Compost
Despite the benefits, many experts warn against using compost as a seed starting medium. Here are some of the main concerns:
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Pathogens: Immature or poorly heated compost may contain fungal or bacterial pathogens that can damping off tender seedlings.
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Weed seeds/pesticides: Compost made from yard waste could have weed seeds. Persistent herbicides or insecticides may also be present.
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Nutrient deficiencies: High carbon immature compost can deprive seedlings of nitrogen. Microbes may also compete for nutrients.
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Poor drainage: Dense, fine compost may become too compacted for good drainage and oxygen flow to roots.
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Variable nutrient levels: The nutrient content of compost is not consistent batch to batch making results unpredictable.
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High salts: Some composts like vermicompost contain high soluble salt levels that can damage tender seedling roots and leaves.
These risks are why many gardeners recommend against direct seeding into straight compost, especially for indoor starting. However, with proper precautions, compost can still be used successfully.
Best Practices for Starting Seeds in Compost
To reduce the risks of using compost for seed starting:
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Use well-finished, mature compost that has heated to over 140°F to kill pathogens.
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Screen compost through 1/4″ mesh to remove chunks, weeds, and debris.
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Test compost maturity with a jar germination test before planting seeds.
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Amend dense compost with perlite, vermiculite or coconut coir to improve drainage and aeration.
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Mix compost with sterile seed starting mix at no more than a 1:3 ratio of compost to seed mix.
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Start seeds in sterile media, then transplant to compost mix after sprouting.
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Use only compost made from materials you know are free of chemicals/pesticides.
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Rinse compost to leach out salts and flush weed seeds.
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Discard any seedlings that appear weak, diseased or abnormal.
By taking these extra precautions, the chances of successfully starting seeds in compost are greatly improved.
Alternative Uses for Compost With Seedlings
If uncomfortable using compost to directly sow seeds, here are some lower risk alternatives:
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Mix into sterile seed starting mix at 25% or less once seeds have sprouted.
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Make biodegradable pots, blocks or pellets from finished compost to transplant seedlings into.
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Top dress older seedlings with a thin layer of sifted compost for added nutrients.
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Water established seedlings occasionally with dilute compost tea to inoculate with beneficial microbes.
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Amend outdoor garden beds with compost when transplanting seedlings to improve soil quality.
This allows seedlings to benefit from the qualities of compost without direct exposure in their vulnerable early stages.
Compost clearly has many beneficial properties that should aid seed starting. However, direct seeding into straight compost does pose some risks, especially for beginners and indoor growing. With extra care taken to manage these risks, seeds can be started successfully in compost. But for many gardeners, it’s easier and safer to wait and add compost into the mix once seedlings are established.
How you choose to use compost with your seedlings comes down to your comfort level with the potential tradeoffs. With proper practices, compost can help provide seedlings an organic, nutrient-rich start while nurturing the living soil web. Just be sure to assess and address any potential downsides for your unique growing conditions.
Can you grow in only compost?
FAQ
Can I start seeds in just compost?
In general, using compost to start seeds works best when the compost is mature and has been sifted, so that it’s a bit lighter and less bulky. If you are starting seeds for growing food, it’s also wise to know where your compost came from: who made it and how did they prepare it?
Is it better to plant seeds in compost or soil?
If you are trying to grow potted plants indoors or outside, compost is a solid choice. When supplemented with liquid fertiliser, it can make sure that your seedlings have all the nutrients they need for rapid growth and make sure they are ready for transplantation.
What happens if you put seeds in compost?
Our compost naturally gets to very high temperatures for long periods of time making seeds in the pile not viable. Everything gets broken down. Backyard piles normally can’t achieve this which is likely why you thought you couldn’t put them in.
Will compost burn seedlings?
Some compost isn’t decomposed into its humus state yet, isn’t made of all the right ingredients, and could be a little smelly. This isn’t the stuff you want to use to start your seedlings because it could be too potent for the seeds and burn them.
Can you start seeds in compost?
Seedlings may grow poorly or suffer nutrient disorders. Excess nutrients, salts, or oils from composts like vermicompost can damage tender roots and leaves. Due to these risks, many gardeners opt to avoid using home compost for starting seeds. However, with proper precautions, seeds can be started in compost successfully.
Can you plant seeds in a compost pile?
Make sure that the seeds you are planting are not from treated plants. These seeds may have herbicides on them that can be harmful to your compost pile and the plants that you are growing. Seeds need oxygen to germinate. If your DIY compost pile is too dense, the seeds may not get enough oxygen and will not grow.
How do you start a garden with compost?
You will want to start with compost as your base. The best compost to use for your seed starting mix is the compost you produce right from your home. Grass clippings, leaves, food scraps, animal manure, and the like will all make a wonderful composted planting medium if given enough time.
Is compost a good seed starting mix?
Microbes – Compost contains beneficial microorganisms that may protect against soil-borne diseases. Cost – Compost can be made for free from yard and household waste versus purchasing commercial seed starting mix. With these benefits it seems compost would be ideal for starting seeds directly in it.
How do you plant seeds in sterile compost?
Make sure seeds sprout well. Amend dense compost with perlite or vermiculite to improve drainage and aeration. Mix compost with sterile seed starting mix at no more than a 1:3 ratio of compost to seed mix. Sow seeds in sterile media first for 1-2 weeks before transplanting into compost mix.
Should you use compost for seeds and seedlings?
For most of us, the answer isn’t clear. For example, some experts recommend avoiding compost when sowing seeds. But many gardeners report outstanding results when they use compost or compost mixes. So who’s right? This article will explain everything you need to consider about using compost for seeds and seedlings. Seedlings are delicate things.