Come learn everything you need to know about potting up seedlings – including tips on when, why, and how to pot up vegetable, herb or flower seedlings. Potting up is a simple but essential step for success when starting seeds indoors or in containers! Chances are, you’ll likely need to repot seedlings at least once (maybe twice) before they get transplanted into the garden. With these tips, your seedlings will grow as healthy, happy, and large as possible.
I’ve also included a demonstration video at the end of this post that shows our process for repotting tomato and cucumber seedlings.
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Transplanting seedlings from their starter pots into larger containers is an important step in raising robust, productive plants. Choosing the right potting mix ensures your seedlings transition seamlessly without stunting or wilting. The ideal soil for transplanting seedlings has a lightweight, loose texture that still retains moisture. It also contains balanced nutrients to encourage root growth.
Why Transplant Seedlings to Begin With?
Seedlings started from seed in small cells or pots quickly outgrow these cramped quarters Their tiny root systems rapidly fill up the limited space As seedlings grow, they require more water and food. Starter soils lack nutrients to sustain fast growth. Transplanting seedlings into roomier pots with nutrient-rich soil enables vigorous root and foliage development.
Moving seedlings into larger containers prevents roots from becoming bound Circling, tangled roots struggle to absorb moisture and nutrients When it’s time to plant in the garden, root-bound transplants suffer more shock and are slower to establish. Transplanting at the right time encourages healthy, spreading root systems and sturdy plants.
Critical Features of Transplanting Mixes
An ideal potting mix for transplanting seedlings has these essential qualities
- Lightweight and loose texture – Avoids compaction and allows tender roots to expand
- Excellent drainage – Prevents overwatering issues that lead to root rot
- Moisture-retentive – Reduces transplant shock by holding water well
- Nutrient-rich – Contains starter fertilizer to gently feed establishing roots
- Soilless or low-soil – Helps prevent damping off diseases
- Balanced pH between 5.5-6.5 – Optimizes nutrient availability for growth
Seeking out mixes with these characteristics sets your seedlings up for successful transfers. Now let’s explore specific ingredients to look for.
Recommended Ingredients
These components create excellent transplanting soil when blended together:
- Peat or coco coir – For moisture retention and fluffy texture
- Perlite or vermiculite – To lighten the mix and improve drainage
- Compost – Supplies beneficial microbes and nutrients
- Worm castings – A natural, slow-release fertilizer
- Starter fertilizer – Lower nitrogen, higher phosphorus blends made for seedlings
Mixing these ingredients yourself or buying a premixed transplanting soil ensures seedlings get the moisture, nutrition, and porosity they need to put down roots in their new, roomier homes.
5 Best Store-Bought Seedling Transplanting Mixes
While you can make your own customized potting soil, these ready-made options efficiently fit the bill:
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Miracle-Gro Seed Starter Mix – Contains fertilizer to feed for 6 weeks and moisture-retaining coconut coir
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Espoma Organic Seed Starter Mix – Enriched with mycorrhizae for stronger roots and a blend of coco coir, peat, and perlite
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Burpee Natural Seed Starting Mix – With coco coir, peat, perlite, and vermiculite to hold moisture while draining freely
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Black Gold Seedling Mix – Formulated with perlite, vermiculite, and long-lasting starter nutrients
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Foxfarm Happy Frog Soil for Seedlings – A nutrient-rich blend of peat moss and forest compost that keeps pH balanced
When choosing a commercial mix, select options specifically formulated for gentle seedling transplanting. Avoid regular potting soils not tailored for seedlings’ needs.
DIY Seedling Transplanting Mix Recipes
You can also easily make your own seedling transplant mix:
Basic Homemade Starter Mix
- 2 parts peat or coco coir
- 1 part perlite or vermiculite
- 1 part compost
Enriched DIY Transplanting Blend
- 2 parts peat or coco coir
- 1 part perlite or vermiculite
- 1 part compost
- 1 part worm castings
- Pinch of starter fertilizer
Mix ingredients thoroughly and test drainage before potting up. Adjust ratios as needed to achieve the ideal lightweight yet moisture-retentive texture.
Giving seedlings an optimal transplanting soil ensures smooth transitions to larger pots. Look for mixes with excellent moisture retention, drainage, and aeration. Lightweight, nutrient-rich blends reduce shock and encourage vigorous growth of roots and leaves. With the right potting soil, your seedlings will flourish when transplanted.
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What is “Potting Up”?
Potting up means the act of transplanting seedlings “up” into larger containers than they were previously living in.
Seedlings are usually potted up into a slightly richer potting soil than they were started in. Sometimes, seedling are also thinned (gently separated or teased apart) in the process, and then individually potted into larger containers.
Keep in mind that once you do repot seedlings, the plants and containers will take up more space under your indoor grow lights – so plan accordingly!
When to Pot Up Seedlings
There is no hard-and-fast rule as to when to repot seedlings. In general, it’s time to pot up once the seedlings have outgrown their current container, which could be within two to six weeks after sprouting.
The exact time depends on a number of factors including the plant type and size, current container, and when you intend to transplant the seedlings outside for good. When in doubt, it’s better to pot up early than wait too long!
- The smaller the container or cells they’re started in, the sooner seedlings will need to be potted up. Plants will feel cramped and overgrown in those fairly quickly.
- Large, fast-growing vegetables like tomatoes or squash will outgrow their container more quickly than something smaller like herbs or lettuce started in the same size pots.
- Check the roots. If a lot of roots are growing out of the bottom drainage holes, it may be time to pot up soon – though few poking through is normal! If you gently lift the entire root ball out of the container and they’re growing in a circle around themselves, it’s time.
- Monitor plant growth and health. Is the seedling still steadily growing? Does the color look good? If it seems to stop growing or turn yellow, it’s probably time.
- When do you intend to transplant seedlings outdoors? If it’s next week or two, then don’t bother potting up! (That is, unless they’re getting really overgrown and bound, then it might be worth it.) Yet, if the seedlings are cramped in their containers and will still be inside for several more weeks, pot those babies up.
These small, slower-growing Tulsi (aka Holy Basil) were started at the same time as our tomatoes! They’re still plenty happy in the 6-pack and will not need potting up before going outside.
We tested popular seed starting soils: you’ll be surprised to learn which one did best!
FAQ
What is the best medium for transplanting seedlings?
Light soil, like promix, works best for transplanting. As you pull each plant out of the soil make sure the root will fit into the pot. If it won’t trim the root. You never want to pile up roots in the pot. It is better if it fits perfectly.
What is the best potting soil for seedlings?
Despite those warnings, the best seed starting mix is quite simple. In fact, you only need three ingredients: coconut coir, compost, and vermiculite or perlite.
Is Miracle-Gro potting mix good for seedlings?
Seed starting medium needs to be very fine (ie few chunks of bark etc.) and have no added chemical fertilizers. Miracle Gro potting mix is not ideal. You’d be better off getting proper seed sowing mix, especially if seeds are small.
How do I choose the right soil for potting up seedlings?
In my experience, choosing the right soil for potting up seedlings is a pivotal step in nurturing healthy, robust plants. Initially, seedlings sprout in a specialized seed starting mix designed to be lighter and more sterile than regular garden soil, which is crucial for their early development.
What is the best soil for seedlings?
The best soil for your seedlings will depend on the specific type of plant you are growing. Some plants, like succulents, prefer a drier, more sandy mix, while others, like leafy greens, thrive in a more moisture-retentive soil. Here are some additional tips to ensure successful potting up: * to avoid damaging their delicate roots.
What kind of potting soil do you use for tomato seedlings?
Again, this depends on your situation. When we are potting up fairly large, established seedlings like the tomato in this example, we use a high-quality organic potting soil, straight from the bag. Potting soil is slightly more dense and nutrient-rich (often contains mild fertilizer) than the seed starting mix the plant was previously living in.
What is the best potting mix for seedlings?
Most seedlings thrive in a slightly acidic to neutral pH range (6.0 to 7.0). Check the pH of your chosen soil mix to ensure it is suitable for your plants. There are several types of potting mixes available, each with its own unique properties. Here are some popular options: 1. Seed Starting Mix
Should I use potting soil or seed starting mix?
If you’re going to put forth the effort to start your seeds indoors, nurture them, and harden them off until it’s time to transplant, seed starting mix will give you greater success rates so you don’t waste seeds (or time). What’s the difference between potting soil and seed starting mix?
What is the best potting soil for plants?
After researching a range of potting soils for various types of plants, we chose Wonder Soil Organic Potting Soil as the best overall choice because it works well for a wide range of plants and includes coco coir and other natural ingredients.