A Guide to Pricking Out Seedlings

Pricking out seedlings is one of those gardening jobs that gardeners talk about all the time. But if you are new to gardening, you may find this rather mystifying. And even if you do know what it is, you might not really know how exactly to go about it. 

This guide to pricking out seedlings should help you make sure you understand the whats, whys, whens and hows of this simple gardening job. 

What Does Pricking Out Seedlings Mean?

Pricking out is the name we give to easing small seedlings out from their seed trays or from among their fellow seedlings where they were sown. Small seedlings are often pricked out and potted on before they are moved out to the garden. 

Why Do We Prick Out Seedlings?

Some seeds can be placed individually into their own pots, plugs, or soil blocks and might remain there during their early stages of growth. 

Often, however, we sow seeds in seed trays or other containers, or into raised beds or the ground, and they may come up too close together. We may need to thin the seedlings out soon after they emerge to give the remaining ones space to grow. 

Some seeds will even germinate into more than one seedling. In these cases, we may need to separate out the individual plants to give them space to grow. 

We will often need to transfer small seedlings, even when they are not too close together, because they need more depth of growing medium for their root systems. Many seeds sown into seed trays will need to be pricked out and potted on into their own individual pots before they may ultimately make their way out into your polytunnel, or outside growing areas. 

If we do not prick out seedlings at the right time, their growth can be stunted, and they may even fail to thrive altogether. Young seedlings can be prone to a fungal issue called damping off, which is more likely to occur if they are not pricked out in time. 

When To Prick Out Seedlings

When pricking out seedlings, timing can be important. We don’t want to do it too early, or the tiny seedlings might not have enough root to thrive. Equally, however, we don’t want to leave it too late and cause them to experience a check in their growth. 

Different seedlings need to be pricked out at different times. However, on the whole, this job is undertaken after the first ‘true’ leaves have formed, but before there are five true leaves on the plant. 

Many new gardeners, even those who are familiar with the concept of pricking out, will think of this as a job that is undertaken after spring sowing. 

But remember, especially when you have a polytunnel, you can sow and grow throughout all the seasons. So you may well find that pricking out is something that you do regularly throughout much of the year as you become more established and determine how to make the most of your space year-round. 

Preparing to Prick Out Seedlings

Before you start pricking out seedlings, it is a good idea to gather everything that you will need. You don’t want to have to put everything down to find other elements once you begin. 

Fortunately, you don’t need a lot to get this job done. You will just need:

• Containers or soil blocks in which to place the seeds that you are pricking out. (Unless you are planting seedlings straight out into a well prepared seed bed your garden.)
• The growing medium for those containers, or to create the blocks. 
• A delicate tool that you can use to gently lever the seedlings from their current growing positions. And perhaps another tool to make the holes in which to place them. 
• Labels (to keep track of what all your seedlings are) and something to write on them. 

While you are pricking out seedlings, it is also handy to have access to water so you can rinse your hands between times, as you might want to label up some seeds before you prick out some more. 

Choosing Containers for Pricked Out Seedlings

Remember, you do not necessarily have to rush out and buy new pots or containers when pricking out seedlings. 

If you want your gardening efforts to be as eco friendly and sustainable as possible then it is always best to reuse pots you already have, repurpose old food packaging, or opt for biodegradable pots.

You might also avoid using containers entirely and opt instead for soil blocks that you can form on your own or make using a specialist soil block tool. Or you can prepare a seed bed in your polytunnel or elsewhere in your garden into which you can transplant your young seedlings. 

Selecting a Growing Medium

Unless you are growing in a seed bed, you will of course also need to think about how you are going to fill your containers. Usually, of course, you will use some form of compost or potting soil. Depending on what you are growing, it may be beneficial to add extra ingredients to the mix to improve drainage or otherwise alter the growing conditions. 

One key thing to remember when pricking out seedlings is that to reduce the shock to the plants, it is best to transplant them into conditions that are as similar as possible to the mix in which they were previously growing. 

You can purchase a seed starting compost, which is specially formulated to be optimal for seed sowing and a seedling’s early stages of growth. (But should be sure to avoid the use of peat which is hugely environmentally damaging.)

But you can also consider making your own seed compost. The precise formulation will depend on exactly what you are trying to grow. But any mix for seedlings should be light, friable, and fine, well-balanced and without any large pieces of material. Make sure there are not larger pieces of woody material as sharp pieces could damage delicate stems on little seedlings. 

Remember, when choosing a potting mix, that you will need to consider fertility level, drainage, moisture retention and pH and match these to the needs of the specific plant or plants that you are growing. 

Tools to Use for Pricking Out

Two tools are traditionally used in horticulture for pricking out procedures, widgers and dibbers. Widgers are shaped like a very thin trowel or spatula and are often used to lift out seedlings without damaging the roots. Dibbers are thin, pointed, pen-like tools used to make holes, and sometimes to firm in seedlings when pricking out. 

However, I would certainly not say that these tools are essential for new gardeners. You can make do perfectly well without them. I usually use a small wooden stick (a lolly pop stick could work just fine) for pricking out, both for easing up the seedlings and for making the holes. You might also use a small spoon and a pencil – or other small implements that you have lying around. 

Seedling Labelling Ideas

It can be very helpful to make sure that before you prick out seedlings, you have some labels prepared. Again, you certainly shouldn’t go out and buy anything for this purpose. You can use many natural or reclaimed materials – things you may well already have lying around. 

Personally, I prefer to avoid plastic where possible in the garden, and so prefer labels made from wood. I have used both lolly sticks collected over the years, and sticks from the garden with a small area shaved off on which I can write. If you don’t have either of these, you might consider cutting labels from an old milk container or another plastic container, or upcycling other old materials. 

To make temporary plant labels, I tend to write on the wood with a black pencil, though you might also choose to use something like a permanent marker pen. 

For labels that will stay in place for longer, and for plant markers in the garden, I have often used a technique called pyrography, which involves burning the words into the wood. 

How To Prick Out Seedlings

• Step One: water the seedlings around an hour before pricking out to make the process easier, and lessen transplantation shock for the young plants. 
• Step Two: Make a hole in the growing medium in new pots or soil blocks in which to place the seedling you prick out. 
• Step Three: Grasp a seedling gently, holding it by the leaf rather than the stem. It is best to hold the seedling by a leaf because if you do accidentally break a leaf, this won’t kill the plant, but if you break the stem it is usually game over. 
• Step Four: Using the tool you have chosen for pricking out, ease the seedling out of its current position. Take care to keep the roots in tact. 
• Step Five: Gently lower the pricked out seedling into the hole you have prepared. Gently firm the growing medium around it, and water it in gently using a sprayer with a fine nozzle to avoid any damage. 

References:

https://www.gardenersworld.com/plants/how-to-prevent-damping-off/

http://www.oakleafgardening.com/glossary-terms/dibber-and-widger/