When to Transplant Seedlings From Seed Tray

Gardening is a journey that begins with tiny seeds and ends with abundant harvests. A crucial step in this journey is knowing when to transplant the seedlings from the seed tray to their new home.

Transplanting at the right time ensures your plants grow healthy and strong, leading to a fruitful gardening season. Here’s everything you need to know about when to transplant seedlings from a seed tray.

What are Seedlings?

Seedlings are young plants that arise from seeds and are often grown in seed trays. They are the first step in a plant’s life and play a fundamental role in gardening.

Common seedlings include vegetables such as tomatoes and peppers and herbs such as basil and cilantro.

Why Do you Need to Transplant Seedlings?

While it may seem obvious why you need to move your seedlings to a new pot, there are several reasons to repot seedlings.

Leave room for root growth: As seedlings grow, their roots need space to expand and absorb nutrients. When you transplant, you will give your seedlings additional room for root growth, which is essential for healthy, thriving plants.

Replenish soil nutrients: Seedlings consume nutrients from the soil they grow. Over time, this source of nutrients is depleted. Transplanting allows fresh soil to be added, providing a new nutrient source for the seedlings.

The soil in the containers can become compacted over time to give seedlings better drainage. This can lead to poor drainage and waterlogged soil. 

Transplanting with fresh soil will give your plants better drainage, allow oversaturated roots to dry out, and prevent the much-dreaded root rot.

Start with the Right Seeds.

Growing food in containers can be very successful, as Patrick has shown us in his videos. You only need a little space to grow.

When you have the correct information about choosing and planting seeds indoors, you’ll be well prepared for a true urban gardening adventure.

It’s time to Transplant

Actual Leaf Development: One of the first indicators that your seedlings are ready to be transplanted is the development of true leaves. Unlike the initial cotyledon leaves, true leaves are the plant’s first set of real leaves.

Root system growth: Check the root system by gently lifting the seedling from the tray. If you see a well-developed root network, it’s a good sign that your plant is ready to move.

Tray Overcrowding: If your seedlings are starting to compete for space, light and nutrients, it’s time to give them more room to grow.

Moving Seedlings from Trays

Using seed trays to help nourish and protect the delicate seedlings in their initial growth is beneficial when starting plants from seeds. Of course, this is a temporary home for the seedlings, and they will need to be transplanted into your garden so they can fully grow and flower.

Tray Size

There are many tray options; some of the most common have 1.5″ wide cells for seedlings, and some can measure up to 2.5″. The more giant cells allow more space in the roots for plant development, meaning the seedlings can stay in the tray longer.

Smaller cells will enable you to plant more seedlings in less space, but of course, they have less room for roots, so they need to be transplanted sooner. As a general guide, after the seeds germinate, they can grow in smaller (1.5″) cell trays for about 2-3 weeks; in larger 2″ trays, they can grow in them for about 3-4 weeks before needing to be transplanted. 

Hardening

When it’s time to transplant your seedlings, if they haven’t already started growing outside, you’ll need to go through a process called hardening off. Hardening off progressively moves seedlings outside to acclimate to direct sunlight, wind, and fluctuating temperatures.

Take the seedlings outside for a few hours the first day, then come back inside, then a little more the next day, and repeat for a few days to a week until you finally leave them outside permanently.

However, do this only if your climate is suitable for the plant. Snow and tomatoes don’t mix, no matter how hard.

Transplant

When it’s time to transplant, moisten the soil in the seedling tray and the soil in your garden. This makes the soil stickier. It holds best when the seedling is removed from the tray and when a hole is made in the garden soil for the plant to enter.

• Gently push up from the bottom of the seed tray to remove the seedling. Be gentle and do your best to keep all roots intact and the seedling undamaged.
• Place the seedlings in the holes you dig in your garden bed and fill in the soil around them, gently pushing down to ensure no air pockets around the roots.
• Then, water them constantly, ensuring the top few inches of soil remain moist for the roots to establish. Once established (you can see visible growth), you can reduce the water according to a standard schedule. A general guideline is ensuring your soil maintains moisture 2″ below the surface.

Time for Transplant

Best seasons to Transplant: Early spring and late summer are usually the best times. Mild temperatures and adequate sunlight provide ideal conditions for growth.

Seedling Age: Most seedlings are ready to transplant when they are 4 to 6 weeks old. However, this can vary depending on the type of plant.

Climatic conditions: Avoid transplanting on extremely hot or cold days. Cloudy days or late afternoons are ideal as they reduce transplant shock.

How To Get Seedlings With Optimal Root Growth For Transplantation. 

The three best ways to achieve a healthy root system when growing your plants from seeds are:

• Use a bottom watering system to avoid compacting the soil. 
• Plant in appropriately sized trays that encourage downward root growth. 
• Pot your seedlings before they become root-bound if you can’t transplant them yet.

How Do I Choose The Best Seedlings From The Nursery?

When choosing seedlings from a nursery to transplant into your home garden, you should keep a few things in mind to ensure you get the healthiest plants possible for a successful garden. 

• You want big, healthy stems and leaves, but not so big that the plant has overgrown its small pot and gets stuck in the roots. 
• Avoid long plants with tall, thin stems. They likely have not received direct sunlight and may fall over when planted outside. 
• Choose smaller, more compact seedlings. They are ready to grow once you plant them.
• Check the foliage for discolouration and damage. The leaves should be uniformly green (unless the plant has variegated foliage). 
• Look at the leaves undersides to ensure no hitchhiking pests, such as aphids or insect eggs. 
• Check plants for signs of disease, such as yellowing of leaves, brown spots, and dry tips. 
• Look at the bottom drainage holes; some visible roots are fine, but if many stick out through them, they are probably root-bound.
• Look for moss or signs of diffuse mould on the soil surface. These are probably signs that the seedlings are old or overwatered, which can cause weak transplants. 
• Squeeze the sides of the pot. It should give a little under pressure, showing that some loose potting soil is still left, which means the roots have little room to grow.
• Too little soil moisture is as problematic as too much, so ensure the potting mix is moist but not soggy. Root-bound seedlings often become hydrophobic and do not absorb water properly. 
• Choose plants that only have leaves and possibly buds. Vegetables and fruits that have already begun to flower and bear fruit will remain small even if given more space.

Preparation for Transplant

Selecting the right tools: Make sure you have the right tools, such as trowels, gloves, and watering cans, ready.

Preparation of the new location: The new location should have well-drained soil enriched with compost or organic matter and receive the proper amount of sunlight for the plant species.

Hardening off seedlings: Gradually acclimate your seedlings to the outdoor environment by placing them outside for a few hours each day for a week.

How Long Can Seeds Stays in Cell Trays?

The length of time a seedling can remain in a cell tray depends on the size of the cells. Deeper and larger cells allow for prolonged growth, as the plant has more space. Otherwise, the seedlings may become root-bound if they are not given adequate root space.

Typically, after sowing the seeds, the cell trays are used for 3 to 4 weeks before transplanting, either to an outdoor plot or a larger container. If you transplant tender seedlings outdoors, consider using a frost blanket to protect them from late spring frosts.

One thing to remember with transplants is to choose the size based on how long the Transplant needs to stay indoors before transplanting into the garden. This will be a factor in selecting the appropriate cell tray for the types of seeds you will be growing.

How to Transplant Seedlings

His first best option is to follow Patrick’s example and do what he does: his tips for transplanting tomato, pepper and eggplant seedlings are an excellent guide.

But for those of us who like to read step-by-step how to transplant seedlings (hands up!), here you have it:

Step One: Prepare Your New Container

Choose a container slightly larger than your plant’s current container and ensure it has drainage holes. Thoroughly clean the container you plan to use with soap and water. Add fresh soil, tamp the container, or press the soil down to eliminate air spaces. You can also lightly wet the soil to ensure even watering once you Transplant.

Some growers like to use a 50:50 mix of seed starting mix and potting soil. The seed starting mix is fertilized very lightly (if at all). Diluting the potting mix with it will prevent young roots from being damaged by soil too rich in nutrients.

Step two: water the seedlings

Water your young plants well before transplanting them. This will help minimize shock and make removing the seedlings from their current container easier.

Step Three: Carefully Remove the Seedlings

This step will vary depending on the type of container the seedlings are growing in. In each case, gently remove the seedlings from their container.

Turn over a pot to carefully remove a young plant, and press the bottom of a flexible seed tray cell to push out the soil plug gently. Methods will vary, but gentle care is always required.

Step four: loosen the roots

If your seedlings’ roots have wrapped around their root ball, gently loosen them with your fingers, a fork, or even a popsicle stick.

Loosening the roots helps them establish a more robust root system in their new container, which creates a vigorous plant.

Step Five: Plant your seedling in its new container

Make a planting hole in the centre of the soil in the new container and carefully place the seedlings in it. Fill around the seedling to anchor it in its new position and, while gently holding the seedling, fill the pot around it.

Fill the container until the young plant is at the same depth as in its previous container. Press down on the soil or gently tap the pot to remove any air pockets.

Step six: water the transplanted seedlings

Once you have successfully transplanted all your seedlings, water them thoroughly. This will reduce plant stress on newly transplanted seedlings and helpfully settle the soil.

If watering reduces the soil level in the pot, add more soil to your container.

Common mistakes to avoid

Transplanting too early or too late: timing is crucial. Transplanting too early can expose seedlings to harsh conditions while transplanting too late can stunt their growth.

Not hardening off seedlings: Skipping the hardening off process can lead to shock as the seedlings are not used to the outdoor conditions.

Inadequate planting depth: Planting too deep or shallow seedlings can hinder their growth. Try to plant them at the same depth they were in the seed tray.

Tips for a Successful Transplant

Use of organic fertilizers: Boost the growth of your seedlings with organic fertilizers that provide essential nutrients.

Companion Planting: Plant compatible species together to enhance growth and deter pests.

FAQ

What Happens if I Transplant Seedlings too Early?

Transplanting seedlings too early can expose them to harsh conditions that they are not yet prepared to handle, leading to transplant shock, stunted growth, or even death.

How Long Do You Leave Seedlings in a Tray?

Typically, the seeds stay in your seed tray for 4 to 6 weeks. After this period, you must transplant the new seedlings into larger pots or outside.

How Big Should Seedlings be Before Transplanting?

They can be transplanted when a few centimetres tall and have at least two sets of true leaves. However, it is essential to avoid transplanting seedlings too early.

What is The Best Soil for Transplanting Seedlings?

Soil with good drainage and rich organic matter is ideal for transplanting seedlings. Adding compost can improve soil fertility and structure.

When to Remove The Seed Tray Cover?

Once the seeds germinate, remove the plastic wrap or humidity dome immediately and get them the light they need!