Garden Duties: Potting Up Seedlings
Updated: Jul 30
Remember those seedlings you started in back in February? Well, they have been growing up before your eyes and are in need of some more space. Unless you plan on direct seeding or taking your baby seedlings directly outside, this is the next step you need to take: Potting Up.
Why should we pot them up?
- If we don't provide the plants with enough space it can become root bound-plant. Meaning they start to circle around themselves on the bottom become tangled and bound up. Root bound plants can actually become unhealthy and die.
- The bigger the plant, the more water they want. They will eventually out grown the cell they started in and dry out quicker than it normally would. Thirsty seedlings need to be potting up to be able to retain some water to help them grow stronger and bigger.
- Probably the most important part of potting up is going from a soilless mix to potting soil. Potting soil has some fertilizer to help feed the plant and help grow strong, stalky, vigorous plants that will provide for you later in the garden.
Equipment Needed Transplant Your Seedlings
Growing or Flat Trays
What is a Growing Tray?
This is a product that I wouldn't skimp out on. A flat tray is designed to hold a 10x20 seedling tray or individual seedling cells. This tray is ideal to use as a drip tray, pouring the water into the bottom to be absorbed up through the soil cells.
Plastic Tray - no holes, used to hold seedling trays or cells.
Plastic Tray - with holes, used for growing micro greens directly into the flat trays.
PROTIP: I advise getting ones that are extra thick and don't bend when you pick them up.
This allows you to reuse them year after year without any of them tearing or breaking. I have learned that lesson the hard way before.
What is a Potting Container?
A potting container is exactly what it sounds like - a pot designed to hold growing seedlings. There are a couple different ones you can use.
Plastic versus Peat Pot.
- Round and Square Pots, also known as Nursery Containers are made of a plastic with holes in the bottom, you transplant one seedling per pot. They come in all sizes 3, 3.5, 4, 5, 6, 6.5, 7, 8 and 10 inches.
They do not hold onto any water, so they drain well.
They do not mold, helping your 2 months transplants stay healthy.
You can bottom water with plastic.
It's reusable, so you don't have to buy it year after year.
Lightweight planting material.
- Biodegradable Pots, I do not recommend. They advertise as biodegradable, sounds good but it also has downfalls.
They hold onto extra water, and don't drain as well.
They do mold because all the extra moisture is being held by the pot.
You cannot water from the bottom.
You have to buy new ones every year... meaning you have to spend a lot of money.
They don't always allow root growth to happen as they predict.
What is Vegetable or Fruit Potting Soil?
In plain-speak, vegetable or fruit potting soil has a light texture, higher nutrients, and usually has fertilizer. Most mixes are comprised of:
- Sphagnum peat moss, which is slightly acidic that provides well-draining and water retention.
- Bark, which improves drainage and airspace.
- Coir, a coconut fibre by-product that works similarity to peat moss.
- Perlite, a volcanic mineral, also helps with drainage and air and water retention.
- Vermiculite, is a silicate material that has been heated and expanded to increase its water holding capacity. They soak up water and nutrients until the plants need them.
- Limestone, garden lime is a rock powder used to raise the pH level of soils high in acidity.
- Fertilizers, they are added to peat-based potting soils because they don’t naturally contain enough nutrients to support optimum plant growth.
- Compost, contains billions of beneficial microbes, and with superior water-holding capacity and nutrient content.
Why use a Vegetable Potting Soil?
- Transplants will need an environment with a steady water supply without waterlogged conditions, which it can provide.
- Potting soil is a light "fluffy medium" with air pockets allowing the roots to have a lot of space to grow.
- Potting soil has more nutrients than the previous sterilized seed starting mix, to help your plants transition into their new home, but it rarely lasts beyond the first month.
Watering is KEY to making sure you have a successful germination.
Guide to watering:
Don't Water from Above: it can damage the plants and they may be prone to disease from wet leaves. It also helps to avoid any soil born diseases as well.
Water from Below: fill the flat trays with water and allow the water to soak up through the soil from the bottom, working its way up to the top.
How to Sow Seeds
1. How to Know When to Pot Up
A few weeks after germination there's a couple of ways that you know when your plants are ready for potting up.
- Are roots starting to poke through the bottom drainage holes?
- Is the plant growing as tall as the container?
- Is the plant flopping over and the leaves starting to droop?
- Has the plant stop growing in a while?
2. Prepare the Potting Soil
- Grab a bowl and fill it with potting soil.
- Add some water into the mix to moisten it up. Mix it evenly with your hands, make sure that it is soppy and not soak and wet.
One reason to pre-moisten the soilless mix is to avoid sinking issues. If you added the soilless mix dry, it technically isn't compact yet. Wetting it before-hand aids it from sinking down into the cell making giving the seedling less medium to grow in.
3. Transplant Your Plants
- Place the seedling pots on top of the flat trays.
- If you are transplanting from:
Germination trays or 6 pack cells → Transplant to 3.5"or 4" pot with the pre-moistened potting mix.
3.5" or 4" pots → Transplant to 6"- 8" depending on how big the seedling has gotten.
PROTIP: Always double to pot size when transplanting to a bigger pot.
- Place some soil at the bottom of the pot.
- Take the plants out of the pot and gently loosing the roots at the bottom. This will encourage the roots to spread in the new soil. Be gentle but in the end we try and avoid waiting until the last minute to transplant when they get all root bound.
- Fill the pot up with the rest of the soil evenly.
4. Make sure to Water Consistently
Now that you have placed your new transplants in a bigger pot don't forget to water them nicely!
I find it best to water from below. You can fill the flat trays with water and allow the water to soak up through the soil from the bottom, working its way up to the top.
Potting mix doesn't dry out as quickly as the seeding start mix. Meaning, you won't have to water them as often as you would have the first time.
That's really all there is to it.
Keep your plants in:
- A safe place
- Away from the cold
- Keep an eye on the soil and don't let it dry out
- Outside during the day, inside during the night
- Don't plant them in a pot or the garden after your last frost has passed