Perlite,Vermiculite, Sand or Grit?

Hello Everyone,

When I'm planting my seeds/seedlings I always use a mix of Multipurpose Compost, Horticultural Silver Sand & Perlite (small amount) mixed together and then I cover the seeds with sieved compost and bobs your uncle my seeds are shooting up! :D

I have noticed on Gardeners World that Carol uses grit on top of her seeds, does anyone else do this? Is there a higher chance of germination? The same goes for Vermiculite, What are your views on it?

Im also interested in the type of seed mixes you use and how you water newly planted seeds. Ive seen that they stand seed trays in water until the top is moist but for me it takes to long so I just water them in normally and I never end up washing seeds away!

Roll on summer, Hopefully we will get a good one. You know what they say ... The good things come to those who wait!

 

I just mix 1/3 sharp sand into my multi purpose compost.
Used vermiculite last year but to me didn't make that much difference.
Think it might make a difference in low light levels though.
I only spray my seedlings with my mister sprayer thingy mi job!

 

I've never used anything other than straight multi-purpose compost, my germination and seedling results are good so why bother with anything else.

If the seedlings are indoors I use a kitchen jug, watering very carefully. If they are in the greenhouse I use a watering can with a fine rose attached. I don't mollycoddle anything at any stage, if what I grow isn't tough enough it's not going to survive in my garden anyway with too many elements against them, and I'm not going to waste time and money fighting them. It sounds harsh yes, but it makes sense to me.

 

I normally just used MPC....But for extra special seeds (mahoosive Onions and gigantic tomatoes) i've gone down the JI seed compost route......i damp the compost first then sow...after that i spray untill pricking out time

 

Hi Kayleigh
When seeding I always (nearly) read the seed packet or look on the net to see what best to do.
Some seeds don't need covering with anything and just need to be firmed into the compost and need light to germinate, others do though, and germinate in a dark place.
So it depends on what your trying to grow.
I think the important thing is to make sure the compost doesn't dry out so I always wrap the the tray in cling film to retain moisture.
The other important thing to note is that most seeds need the soil tempreture to be warm enough for germination. I find an airing cupboard invaluable.
Vermiculite is good because it allows light and retains moisture but so does cling film.
a layer of grit doesn't allow light and maybe a good thing for some seeds, but there are alternatives. also there are considerations whether you're trays are in a window sill or a greenhouse that is unheated/heated.
Cheers Rob

 

Didn't see that, but it might be that it is for seeds that take ages to germinate - if you don't do something like that the compost surface will be covered in moss and the seeds won't get through.

I use:

Nothing: only for seeds that germinate quickly.

Vermiculite: particularly for small seeds, and seeds that need light to germinate and must only be lightly covered; its very light, somewhat transparent, and stops most algae-type growth up to medium term.

Grit: things that take ages (more than 6 months) to germinate.

I only use soil base seed-compost for seed sowing. I find it much easier to prick-out from as the soil falls away from the roots

For things that grow quickly, and need potting on, I prick-out into multi-purpose.

For things that are slower, and likely to stay in a 9cm pot until planting out, I add 10% (by volume) Perlite to keep the mix "open" as I find it greatly reduces the compaction that you get with multi-purpose over a couple of months. It does increase the drainage, and thus the amount of watering that is needed.

 

P.S. I only ever water seedlings from below - I stand them in a tray of tepid water for 5 minutes. Watering from above encourages algae to form, and for seedlings may increase the risk of damping off. Don't use rain water, it has too much "muck" in it from the air / roof, tap water is much more sterile - leave it stand for a while to acclimatise temperature and for the chlorine to evaporate.

For seed being germinated I cover with a clear plastic dome, or cling film, and spray the surface with a hand-mister if I think the surface is not maintaining enough moisture (but with a cover it should be 100% humid in there )

 

Thanks everybody, Vermiculite is sound a good idea for seeds needing a light covering!

 

i've only ever used multi purpose/potting compost, it's always done the job so never really had reason to try anything else.

may i ask do you guys do anything to get your compost to 'settle' before sowing? i've always very lightly pressed on the surface (to ensure there's no air pockets and whatnot) but apparently Monty Don doesn't! he just taps the seed tray a few times on the work bench. what do you do?

did what i just say make any sense at all?

 

I just use multi purpose, often with a mix of perlite and/or vermiculite. Like Kristen I use grit to cover seed that takes a long time to germinate (ie; Cardiocrinum). I always fill the pot before sowing and pour boiling water through it as a crude means of sterilising - sow the seed once it has cooled down. If they're not in my heated propagator I put them in a zip lock bag. If they do dry out, then I mist the surface with water that has been boiled.

More and more though, I am using the paper towel method of germinating.

 

I fill the container "overfull", take a flat instrument - usually another seed container! - and scrape off the excess compost so the container is plumb-full, very (almost no pressure) press it down with 4-fingers "flat" so-to-speak. This is just to make sure no air pockets. Usually the corners push down a bit. Then I sift compost onto the container (which now has a small gap between compost and rim), and again scrape off the excess. This top-coat is not compressed by left "fluffy". I then stand in warm tap water for 5 minutes, and take out to drain. Compost has usually sunk a bit. Then I sow seeds and cover with propagator lid / plastic bag.

Is this just a bit of damp kitchen paper lining a container (something like a Ramekin) with cling-film or other "lid"? Or perhaps in a zip-lock bag?

 

Folded damp kitchen towel in a zip-lock bag.
I wouldn't use it for small seed, or for seed that has a long germination period.
It can be a little bit of trial and error too. In the photo below are two different seeds that someone bought me back from Tanzania. The beige ones germinated at about 40% in compost in my heated propagator, the black ones did nothing. But in paper towel I have 100% germination of the black ones after just five days.

 

Interesting, thanks. The air-and-water ratio must be excellent using paper-towel method, and no chance of it drying out during germination. I have used it a lot for big seeds like Cannas, and things like Sweetcorn, Parsnip seed, Broad beans ... Brugs too ... perhaps I should move more wholesale to it, it would solve a lot of space issues in Spring time with seed trays vying for space in the propagator - I could go straight to prick-out stage instead.

Why not for small seeds? Any experiment that you have tried side-by-side? I'm thinking the prick-out would be difficult, but maybe there is a way around that?

 

Never tried, but my thinking is that small seed is generally surface sown and may be prone to rot using this method...............

 

I'll give it a try. I'm thinking of the sorts of seeds I get which are 5 or 10 to a packet, and are the size of Poppy seeds. Things like Lobelia "dust" would be a nightmare to prick out! but even if tiny if there are only 5 or 10 seeds it should be possible to prick out without too much angst - even if have to cut the paper into squares and plant "complete"