Kitchen Garden Forum

What does everybody do about the green mould which sometimes develops on compost in trays of seedlings? Is it due to over watering (of which I suspect I may be guilty in the desire not to let my seedlings die of thirst). Does it cause any harm? Would it be better to aerate the compost where possible if there's enough space between seedlings to do so?

Hi Primrose,
May I enquire as to which compost you are using? It itself the green mould is very unlikely to harm your plants . When taking cuttings and placing them in the misting unit they invariably get green mould/moss and as far as I am aware it has not affected my plants over the years.
I suspect that it is due, as you say, to over watering.
MORE PLANTS ARE KILLED OFF BY OVER WATERING THAN UNDER WATERING
I think that you should buy a small hand operated mister and only ensure that the surface of the compost is MOIST. When the seeds are sown the compost should be fairly moist and if you go round with a mister and keep the surface moist then this will really ensure that you are maintaining the moist condition needed.
I use a very small spray unit giving only a mist and I only use about 1 litre a week to keep god knows how many seedlings going well.
Once they are potted on then I increase the amount of water but still use very little. Seedlings do not have the capacity to take up much water, if any at all, so all you are doing is depriving them of the oxygen so critical at the roots by saturation.
JB.

Johnboy, I'm using a Levington's General Purpose compost, and I suspect you are right about the over watering. I shall get myself a hand mister as you suggest. I've ought to have been gardening for enough years now to have learnt this lesson! I guess it's the fact that when sowing we're always urged never to let the compost dry out and when using any kind of hand watering device it's almost impossible to limit the amount of water which comes out.

Hi Primrose,
So Levingtons is a Peat Based MP compost. I use Vitax peat based MP compost but there is probably no difference.
If anything when you are going to sow seeds you should use your new found toy very useful to mist the compost as you mix it. I always rub my seeding mixtures through a riddle and I mix in a very small amount of Vitax Q4 fertilizer and a very small amount of super phosphate and as I mix those in I fine tune the compost for moisture. You will find it very easy with a mister. If you take a handful of compost and squeeze it it should be just able to crumble. If it sticks together it is really too moist.
I fill my modules and tamp down lightly with a hand brush then sow my seeds and then top up the modules with compost then with the hand brush very lightly tamp it to just firm. I then mist over the top without saturating and really I only ever mist again if the surface has dried out.
I am probably trying to teach my grandmother to suck eggs but whatever.
The term Grandmother is used with extreme reserve.
JB.

Hi,
Thanks Johnboy - it really is good to be reminded of basics such as how much water to apply to seed trays. I suspect I have been over watering as well - will apply more caution and dig out the demister which is always stolen for the bar-b-q and NEVER put back!!!
Regards
Hilary

Hi Hilary,
I think that many people are so much in a hurry to get seeds going that they forget the basics. Really these basics should be imprinted in every gardeners brain. Sowing seeds is very easy but everybody should pause and think what that seed needs to germinate it then through to the next phase up to potting on. At potting on the regime changes slightly the plants have found there feet (roots) and are becoming hungry so further nutrient is required. The potting on mixture should contain more fertilizer than was put in the seeding mixture. In the seeding the amount of fertilizer is but a token and may or may not have been needed but the super phosphate, again a token amount, will be there for when the roots a capable of taking in nutrient. When producing young plants it is the root formation that is all important. If you get the root structure correct then when you finally plant your seedlings in their final growing position they will thrive. So often people think that because they have good top growth that that is the be all but when they plant out the plants flop and this is because there is an insufficient root structure to take up the nutrient for the amount of top growth. This is all very easy but many people simply forget to apply these basic rules. This is why I use plugs to grow most thing because the is no root disturbance and they are a doddle to plant up or plant out. The amount of nutrient you have used goes with the plant to its final planting and the plants do not take what is sometime a fatal check it growth.
JB.

Thanks for that explanation Johnboy. I think you've stated very clearly some of the basics which we can tend to overlook. You're probably right that some of us tend to judge the health of a young plant by what we see happening above the soil rather than what's developing underneath. I think I will approach my seed sowing more thoughtfully in future, having often previously been guilty of putting the seed in pots or trays "and then giving them a good soak", especially when some seeds are rather hard. I've been imagining them needing plenty of moisture to break down the outer casing of the seed. Lesson now learned, I hope.

Hi Primrose,
I feel that is best to give your germinating seeds the very best conditions possible and this is why I am in general against the use of propagators for the germinating of things like Brassicas. They simple do not need it and are best left for nature to takes it's course rather than force them. By forcing you get into 'the lovely top growth' trap.
Certainly there are things that will need a propagator. I find that Celery and Celeriac are two and also several plants such as Tomatoes, Peppers and Chilli's and Aubergine Plants that should never be allowed to go below 10C during their stay with us. I am fully aware that these plants will grow below these temperatures but you will never get the best out of them and also with Tomatoes you can actually get a marked difference between these and plants grown at the right temperature.
I pregerminate quite a few seeds but say with Parsley they go into a propagator until you have a show of a few anemic wispy seedlings then they are taken out and placed on the bench of a cold tunnel and within a week you have masses of green shoots. These then grow on in the cold condition but if you left them in a propagator they would be useless within a week. With most normal vegetables just let them do their own thing.
JB.

Thanks for the timely reminder about not over-watering. It isn't always easy to know whether to water them or not if the top of the compost has dried out, and I usually pick the tray up and see if it feels light or heavy before watering.

I've just been to a nursery today and in their greenhouse the tomato seedlings looked much drier than I would have been happy with, so I made a mental note to give mine a bit less water. I did wonder if they were keeping them on the dry side to slow their growth a bit and keep them sturdy so they aren't too leggy when it's time to plant them out.