After germinating seed, when should the seedlings be potted?
If you germinated seed on top of potting mix in a small pot then there is no need to transplant the seedlings at this stage. They can happily grow together in a community pot until they are about 2 years of age. I have included a photo of some happy seedlings that are about 18 months old.
If you have germinated the seed in a small cell tray, when would you transplant the seedling?
Once the seed has a root growing down into the mix and the root is at least 1 – 2cm long, and there is a green leaf growing upward and the leaf is least 1 – 2cm long then I transplant the seedling. Of course you can wait longer until the seedling is larger but the root has a limited chance to grow downward in a cell tray. If possible, it is better to germinate the seeds on the top of a pot and then there is no need to transplant them. In my case, as I have so many seeds to germinate, I use cell trays so I can place them on heat mats to hurry up the process.
What do you transplant them into?
If I have to transplant baby seedlings, I do this very gently as they are fragile at this stage. I mostly use 50mm native tubes as I can fit 50 tubes in one stand, and I am placing 2 seedlings per tube. Seedlings are quite happy sharing with a friend or if you are planting into a small pot, they are happy in a community pot with a few others. I have included a photo of seedlings in my seedling shade house happily sharing. I also use 100mm pots as community pots.
I pot them into seed raising mix that I make up, though the store bought one is fine. Poke a little hole in the mix and place the seedling root into the hole. Gently firm the mix around the seedling and then fully water so all mix is wet.
Where do I place the pots and how do I look after the seedlings?
Keep the seedlings out of the sun completely. The best place to keep them is in a shaded and sheltered position, preferably on the south side of your house under the eaves, under a verandah, or in the house is good too. When my seedlings are first repotted after germination, it is still winter here in Melbourne. I feel it is too cold for them in the shade house, even though it has a solar weave cover over it. The seedlings have lived their short lives on a heat mat, so I keep the pots in my germination area until spring. Once I feel the temperatures rising and the frosts are over, I take the pots down to the shade house.
Be careful not to place the pots where the seedlings may come into contact with hail, heavy rain or wind. As mentioned, they are a bit fragile at this stage.
Thoroughly water the pots once or twice a week. Seedlings like to be kept very slightly damp but not wet. Wet will kill them. They should not be sitting in water or a saucer of water. The water needs to drain out the bottom of the pot. If you feel they are drying out too much, give them a spray each day with a water spray bottle, or give them a light spray with a hose.
Should I fertilise them?
The seedlings will still have their seed attached for about 6 months and they get nourishment from the seed. Most seed raising mixes have a slow release fertiliser in them so I don’t think it is vitally important to fertilise them in the first 6 months. If I am using a foliar spray fertiliser on plants in the same shade house then I will spray the babies as well.
Once they are 6 months old then it is a good idea to give them a weakened solution of a soluble fertiliser regularly. There are many good fertilisers available but the ones I have used are PowerFeed and Seamungus. In a perfect world, I would use the weakened solution on the seedlings once a month in Spring, Summer and Autumn. Unfortunately I am not disciplined enough with too many seedlings so I make sure they also have Osmocote.
What about Pests and Diseases?
With seedlings, the worst pests are caterpillars, mealy bug and fungus gnats, but you may also experience problems with other pests depending on where you live. A caterpillar can decimate a little seedling overnight. Mealy bugs and Fungus Gnats can cause damage that can result in rot and the seedling ‘falling over’. Prevention is better than cure. Spraying regularly with Eco-oil can go a long way toward prevention. Yellow sticky traps are good for killing fungus gnats.
When do I repot them individually or plant into the garden?
I would not plant the seedlings in the garden until they are about 2 years of age, unless they will be in a well-sheltered position and safe from frost, storms, sun, hail and heavy rain. It also doesn’t hurt to use a small bamboo stake or similar and a soft tie to secure the seedling so there is no movement when you wriggle the seedling. This will help them to grow roots and establish. Make sure they go into a well-drained soil and water them in.
I find the period between baby seedling and 2 year old is a dangerous time to repot seedlings. They do not like to be disturbed and need at least 3 leaves before I would attempt to repot. This is why I do not sell seedlings on my website until they are at least 2 years of age.
If you are planning to keep your plants in pots for the future, you can leave them in the community pot until they are bulging to get out. Although if they are left too long, then there is no goodness left in the seed raising mix and also the roots are limited as to where they can grow.
As I usually use 100mm pots for community pots of 5 – 10 seedlings, when I repot them at 2 years of age, I would most likely pot one seedling per 100mm pot. If some seedlings are still a bit small even though they are 2 years old, then I would keep all the small seedlings in the community pot for a longer period of time and just repot the larger seedlings.
With seedlings, it is better to keep them in a slightly small to snug sized pot than to overpot them.