This is likely what you will need to do before moving plants from seeds to the garden: pot up the baby seedlings. Maybe even twice! Your individual potting up needs and timing will vary. That will depend on the size of the seedling pots you used to begin with, how fast your plants are growing, and how long it has been since they sprouted. The act of potting up, when done right, helps your plants thrive!.
This article will discuss the what, why, when, and how of potting up. You can watch a video at the end of this post that shows how we pot up tomato and cucumber seedlings.
If you don’t want to read about why and when to pot up, click on the link below to go straight to the “how to” and video.
You’ve lovingly tended to your seedlings, giving them the perfect conditions to sprout and grow Now it’s time to transplant them into larger containers. Choosing the right potting mix is critical at this stage to prevent shock and support ongoing growth The best soils for transplanting seedlings have certain qualities that enable smooth transitions.
In this guide, we’ll cover:
- Key traits to look for in potting mixes
- Recommended soil ingredients
- The 5 best store-bought options
- DIY soil blend recipes
Follow these tips to pick potting soils that will set your transplants up for success!
What to Look For in Potting Soil for Seedlings
Here are the most important characteristics to consider when selecting transplanting mixes:
Lightweight & Loose Texture
Avoids compaction around delicate roots Allows for easy transplanting.
High Porosity
Excellent drainage prevents overwatering. Promotes beneficial airflow to roots.
Balanced Nutrition
Contains starter fertilizer to feed establishing roots without burning.
Soilless or Low Soil
Reduces risk of diseases Provides consistent growing medium,
Moisture-Retentive
Holds water well to reduce transplant shock. Misting less needed.
pH Between 5.5-6.5
Ideal acidity range for nutrient availability. Prevents nutrient deficiencies.
With these traits, seedlings will transition seamlessly to new containers with no stunting or wilting. Now let’s look at recommended ingredients.
Key Ingredients to Use
The perfect transplanting soil contains a blend of the following components:
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Peat or coco coir – Excellent moisture retention. Provides fluffy texture.
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Perlite or vermiculite – Lightens the mix and improves drainage/aeration.
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Compost or humus – Adds beneficial microbes and nutrients for growth. Start with 10-30% compost.
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Worm castings – Natural slow-release fertilizer full of micronutrients.
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Starter fertilizer – Look for lower nitrogen, higher phosphorus options marketed for seedlings.
When blended well, these ingredients create an ideal growing medium for your newly transplanted seedlings. Now let’s look at specific products.
5 Best Store-Bought Potting Mixes
While you can certainly mix your own custom soil, these ready-made options are excellent timesavers:
1. Miracle-Gro Seed Starter Potting Mix
- Contains fertilizer to feed for 6 weeks
- Coconut coir retains moisture
- Lightweight and fluffy texture
2. Espoma Organic Seed Starter Mix
- Mycorrhizae for stronger roots
- Coconut coir, peat, and perlite
- Low salt and nutrient starter charge
3. Burpee Natural Seed Starting Mix
- Coconut coir, peat, perlite, and vermiculite
- Holds moisture while draining well
- Naturally balances pH
4. Black Gold Seedling Mix
- Long-lasting starter nutrients
- Contains perlite and vermiculite
- Resists compaction and drains freely
5. Foxfarm Happy Frog Soil for Seedlings
- Nutrient-rich blend fosters growth
- Contains peat moss and forest compost
- Balanced pH between 6-6.5
When choosing among commercial mixes, read labels closely and look for the seedling-specific options within a brand’s lineup. They will be formulated for gentle transplanting.
Custom DIY Potting Mix Recipes
You can also easily blend your own custom mix at home with these recipes:
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 the ingredients together thoroughly before filling containers. Test drainage by watering the mix and ensuring no standing water remains after several minutes. Adjust ratios as needed to achieve a fluffy texture that retains moisture but drains freely.
The ideal seedling transplanting soil gives baby plants both the moisture and air they need to put down roots in their new home. Follow these tips to find or create the perfect mix. Soon you’ll have vigorous seedlings ready for the garden!
What is ‘potting up’ seedlings?
Potting up couldn’t get any more literal. It is simply the act of transplanting seedlings “up” into larger containers than they were previously living in.
To be honest, potting up is a task I dread for some reason. It isn’t all that difficult, but does take a little time and effort. Despite having a lot of other things I need to do around the farm, I always put this task off until it’s really important. Because I know this about myself, we start seeds in bigger containers to make sure we (and the plants) have the best chance of success from the start. This reduces the urgency to do it so soon after germination. We’ll talk more about container sizes shortly.
Putting seedlings in pots as they grow gives them the best chance to get bigger and stronger, feel less stressed, and live their best life! By potting up seedlings into larger containers, it enables their roots to continue to grow without getting root-bound. A root bound-plant is not a happy plant. Plant roots get tangled and “bound up” when they are squished so much that they start to grow in circles around themselves. This can reduce the roots ability to spread out and flourish after they’re planted out in the garden. The health of the plants is directly linked to the health of their roots, so these plants are also less likely to do well.
Plants with tight, bound root balls can be gently loosened during the time they’re transplanted. However, this could either help them, or harm them. For some plants, ruffling the roots is fine. Breaking up that ball can help the roots spread out the way we want them to. However, some don’t take a liking to this treatment. They might even get a bit of transplant shock from it. So, we try to keep the roots from sticking together in the first place so that we don’t have to disturb them as much later.
2. Seedlings need to be put in pots because their roots need more water as they grow, so they dry out faster. A small 6-pack with soil and seeds that haven’t sprouted yet will keep water for a lot longer than a small 6-pack with adult seedlings that are thirsty. It can be boring to take care of seedlings, but it’s even more boring when they dry out every day!
3. Lastly, the potting up process feeds the seedlings! If you started seeds in straight seedling mix, or a mix with primarily seedling soil like we do, chances are they’re hungry. Seedling soil is very fluffy and pretty devoid of nutrients. Even if you have been feeding with an occasional dilute seaweed extract, the plants will definitely enjoy a slighter richer, heartier soil now!
When to pot up seedlings
When to pot up will depend on the gardener, the situation, and the plant. The best time to pot up seedlings depends on how big their containers are, what kind of plant they are, when they’ll be planted outside, and how quickly they are growing. There is no set rule like, “You must pot up within 33 days of germination”….
The best time to pot up a seedling greatly depends on the size of container you started it in. Smaller containers, like those trays with dozens of cells each, are going to require potting up sooner. Plants will feel cramped and overgrown in those fairly quickly. As I mentioned before, we usually avoid starting larger vegetable seedlings in tiny-hole trays. By starting them in slightly larger containers, like these reusable 4” nursery pots, we don’t need to pot up until about 6 to 8 weeks after germination. After that, we’ll move them into 6-inch or 8-inch pots.
The various seedling containers we use. We’ll usually start seeds in the
Then why don’t we just start the seeds in those bigger 6 to 8-inch pots from the start? That way, we won’t have to pot them up at all, right? Well, it’s not quite that easy. In the first place, it will take up a lot of room to start seeds in big pots. You won’t be able to fit as many pots on your heat mats and under your grow lights, which is very important for germination and the first few weeks of life. That means less plants, which is never a good thing.
Also, tiny seeds and seedlings don’t necessarily want to be swimming in a huge sea of soil. It is easier to overwater, and their roots might struggle to develop. They do like to be hugged, just a little. Another great step that helps plants grow is moving from seedling mix to richer soil. If we started in big pots, we wouldn’t be able to do this.
The timing for potting up also depends on the plant itself. Bigger plants, like tomatoes, will need more room faster than smaller plants, like herbs planted in the same-sized pot. Tomatoes grow much faster than peppers, so we always need to pot up our tomatoes earlier.
If you plan in advance, you could try to start certain vegetables, herbs, and flowers in appropriate size containers. For example, we start most of our flowers, herbs and leafy greens in 6-packs, and the other bigger veggies in 4” pots. We have found that by doing this, the flowers and herbs are usually okay in their 6-pack until the time they need to go outside, and may not need to be potted up at all. Squash grow very quickly and don’t like their roots disturbed. Therefore, we start those straight in larger 6” pots to give them plenty of space. We start them only about 3-6 weeks before they’ll be planted outside, so we don’t need to pot them up at all.
We started this small Tulsi plant, also known as Holy Basil, at the same time as our tomatoes. It is still doing well in its pot.
Potting Up Seedlings 101: Easy Seed Starting Tip!
FAQ
What type of soil is best for transplanting seedlings?
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