Reusing compost

So far so good - not managed to kill any planty things yet
Going to be transplanting some of my seedlings into their own pot tonight or tomorrow, but what do I do with the compost they're in just now? Do I put that in the new pot, or use new compost? Or a bit of both?
What do you do with compost that has been used? Put it back in the compost bag, or pop it in the compost bin?

G

 

Hi SF

Use the new compost, as it will contain more nutrients etc , fresh is best !!!! with seedlings .

The old compost you can put on the veg patch or around your shrubs etc or the compost bin


Spruce

 

If it's from a tray of seedlings I'll use it to pot up plants from cell trays into 3" pots or sow large seeds like peas, french bean, runner bean seeds etc. I'll avoid re-using to sow smaller seeds or for transplanting seedlings because I'm wary of infection/spoilage organisms, and possible adverse effects from bits of decaying plant matter left in the compost.

As I sow in 'multi-purpose' compost that will have enough nutrients in for tomatoes, etc. to grow on in 3" pots to planting out stage, I'm fairly certain a few seedlings will not have exhausted the nutrients by they time they're at pricking out stage.

 

Don't know about everyone else but I always use fresh compost for potting on my babies, the used stuff goes in the compost bin, I use seed compost to start my seeds off in which is low in nutrients so no good for growing plants on in.

 

If you're transplanting seedlings .... loosen the dirt/soil/compost (call it what you will) by inserting something - I use an old wide bladed knife - into the compost a short distance away from the seedling and gently ease it loose from the bottom. When sufficiently loosened, the seedling can be teased out of it's current 'home' with, ideally, as much of the original compost attached as possible since this means the roots aren't disturbed any more than is absolutely necessary and all of it can be inserted into the new pot along with the seedling.

I would always transplant seedlings into pots filled with new compost, since growing plants need all the nutrients they can get. That said, I suppose there's no reason why you couldn't mix a little of the original compost in with the new but I don't think I would allow it to make up more than about 10% at most.

As for the 'used' compost - I certainly wouldn't advocate putting back in the bag, it might have picked up or contain at best, weed seeds - at worst some airborne disease spores. If I'm merely re-potting an existing, healthy, well-established plant I might mix a little of the seed compost into the re-potting mixture (just on the 'waste not, want not' principle), but again it would only be a small percentage.

Don't, whatever you do, just dump it in the compost bin - use it around other plants in the garden, it may still contain some nutrients and even if it doesn't, it'll still be useful if only as a mulch

 

Thanks everyone... Nearly made a rookie mistake lol, so I'll save it all up and pop it in the compost heap - would put it on the veg patch, or on other plants, but... erm... these are my first plants (not including weeds, more weeds and some strands of grass interspersed between more weeds lol). Once I get the rest of the garden sorted, then I can spread it on the plants(thats along way off in the future!!!)

G

 

Number crunching time:

The compost from one seedtray will fill 10 3" pots, tomato seedlings at pricking out stage weigh 0.25g and tomato plants in 3" pots ready for planting out weigh 25g.

So if 10 pots of multi-purpose compost has sufficient nutrients to produce 250g of plant, the same amount in a seedtray should be capable of producing one thousand 0.25g seedlings.

So it's pretty obvious there's absolutely loads of nutrient left after pricking out even a hundred or so seedlings.

 

Ta for that mathematical effort, way beyond me, so I'm sure you're right!

Even in the unlikely event that there wasn't much nutrient left, couldn't it be made good by watering with a soluble fertiliser, such as the heavily-advertised one which promises miracles?

I'm hoping so, anyway, as I'm getting a bit stingy with the compost and like to reserve it for really deserving cases like new seedlings and things that need coddling.

I've potted up all my dahlia tubers in mixtures of old and new compost and I'm sure they haven't noticed.

 

That's another worthy re-use that I'd forgotten about. And thinking about a previous thread where
us gardeners were under attack from conservationists about our use of peat-based compost, it might help counter their arguments if we can explain that it's used efficiently as possible.

 

I often use "left-over" compost to plant bulbs in...

 

Here's another use for spent/used compost:



They love pecking, scratching and rolling around in it!