Potty About Potting On
I will start by saying that pricking out seedlings and potting them on, is by far one of my favourite gardening jobs! Even after trays and trays of seedlings, it’s just one of those jobs that I find very therapeutic (but then I also enjoy weeding, so what does that tell you?!).
This year I had packets and packets of old expired seed and as you may have guessed by now, I don’t throw anything away. So I decided to sow the entire packet of seed into a tray on the assumption that perhaps only a few of them might germinate. Much to my amazement the germination success rate was incredible.
Altogether I pricked out and potted on 94 California poppies, 71 Gaillardia ‘Goblin’, 47 Emilia ‘Irish Poet’, 122 Calendula and 26 Sunflower ‘Mezzulah’ (and lets not even mention how many basil plants I eventually ended up with this year). That was certainly a lesson in expired seed packets but I was in my element. The only struggle was finding space in the greenhouse for them all once I had pricked them out.
Now lets break this down by discussing some of the terminology for all the new gardeners out there and to refresh the memory of some of you more experienced gardeners.
What do we mean by ‘pricking out’?
Pricking out is an essential part of the process of propagating/removing small seedlings that have been sown in a tray. (This is not to be confused with ‘thinning out’, which is a different process entirely).
When do you ‘prick out’ the seedlings?
Once the seedlings have developed their ‘true leaves’ which are the second set of leaves after the emerging leaves.
Why do you ‘prick out’?
Once germinated the seedlings start competing with one another for space and it’s important to prick them out as soon as they are ready so they can establish a strong root system.
What do we mean by ‘potting on’?
Potting on is the process of taking a small seedling, pricking it out and giving it it’s own individual pot. And further potting on maybe required throughout it’s growth, before it is actually large enough to be planted out into it’s final position.
Pricking Out and Potting On Guide
Start by preparing the pots that the seedlings are going to be transplanted into. I would suggest potting on into a 9cm (3-4”) diameter pot
Fill your individual pots with growing medium right to the top, give the pot a tap. This helps settle the growing medium and you should now have a small gap at the top of the pot
Not all the seedlings may have their ‘true leaves’ as quite often they germinate at different rates, so choose a strong looking seedling with it’s ‘true leaves’
Using a dibber to loosen the growing medium around the roots
Lift the seedling out by holding one of the ‘true leaves’ between a finger and thumb
Gently ease the seedling out, trying to keep as much of the growing medium around the roots as possible (it’s very important to be as gentle as possible during this process as the roots and stem can easily be damaged)
Using the dibber make a hole in the centre of the growing medium of the individual pot
Gently place the seedling into the hole you created (at this point the urge is to firm the soil around the seedling but this is a mistake, again its very easy to damage the roots)
Continue to hold the ‘true leaves’ whilst you use your other hand to gently shake the pot so that the growing medium gently cushions the seedling into place
Whenever you are transplanting or potting on it’s important to water in. With new seedlings I prefer to do this by standing the pots in a tray of water and allowing the growing medium to soak it up, this way the seedlings are not disturbed
The seedlings then get transferred to the greenhouse or a bright window ledge but it’s important not to allow the growing medium to dry out
Check the growth regularly, specifically the root growth and if there are visible roots coming out of the bottom of the pot, it’s time to check the root growth by tipping the plant out and checking the root system. If the roots are strong and white, either pot them on into a larger individual pot or plant them out. If they haven’t developed strong roots let them remain in the same pot for a little longer
Some other interesting points to remember when pricking out and potting on are;
Hardening Off - It’s important to note before planting out that the plants will need ‘hardening off’. This is a gradual process that allows the plant to get used to outdoor conditions. Without this process the plants get a shock when planted out and whilst they may recover, the growth will be stunted. Plants that are grown indoors need to acclimatise to cooler temperatures, change in humidity and an increase in air flow (botanically speaking the effect of hardening off allows the plants leaf structure to thicken). This process usually takes around 2-3 weeks. If the seedlings start out life in the greenhouse, they then move to a cold frame and then outdoors perhaps under a cloche or fleece and then without. If you don’t have a greenhouse and cold frame and you are raising your seedlings on the window ledge, start by placing them in a sheltered spot outdoors during the day and then bringing them in at night and slowly increase the frequency until they are strong enough to be planted out.
Feed - By the time that the seedlings produce their ‘true leaves’ and are starting to compete for space in the grow tray, they will also be lacking in nutrients. It’s important when preparing your growing medium for potting on, that you include in your mixture a general fertiliser. This could mean mixing in some home made compost or leaf mould. Or you may prefer a liquid feed such as comfrey. Just as watering is important so too are the nutrients that the plant will be looking for to enable strong growth.
Potting On - This process is also referred to as ‘potting up’. Potted plants can become deficient in nutrients as they grow and potting on enables you to add fresh nutrients in the way of new soil to avoid the plants decline in growth. The one thing to be mindful of when potting on is root disturbance, not all plants appreciate this.
I hope you have found this guide useful. If you have never done this before visit our Starter Grow Kit and gift sets for everything you need to get you started. Give it a go and I promise you, you will be hooked and growing everything from seed year after year!