Compost driving me mad!

[Penellype]

I'm continuing to have real problems with bought compost and I really don't know what to do about it. I am becoming increasingly convinced that in bags of compost there are pockets that are simply poisoned with weedkiller, presumably from green waste (probably grass cuttings from treated lawns). I have a bag of compost that I bought earlier in the year that I have been using to grow various seedlings, with mixed results. While some plants (including peas, beans, tomatoes and courgettes) have grown well from this bag of compost, some of the peas and beans simply haven't germinated, and neither did most of the courgettes and some of the tomatoes and peppers sown in an earlier bag of compost. Towards the end of the sowing season I had pots of compost that had been tried with beans and failed, and I had some saved seed from some peas that I wanted to check for viability as the pods had been picked green and dried. I decided to plant 4 peas in one of the pots that had failed to grow beans. I put another 4 peas to chit on damp kitchen paper. These started to grow roots in a couple of days and I planted them in another pot that had failed to grow beans. I dug the ungerminated beans out of the compost before sowing the peas. All 8 seeds failed to grow, including the ones with roots. This mirrors exactly what had been happening with beans that I chitted earlier in the year.

I also had some saved seeds from some mixed brassica salads that had bolted in the spring. I wanted to check the viability of these seeds as they were also picked before the pods were completely ripe as the plants were in the way. I sowed pinches of seeds in 15 small modules in my propagator, using compost straight out of the bag. The result a couple of weeks later is that I have one seedling. After the pea experiment I decided to double check before I throw the seeds away. I had some used compost saved from last year's fence pot plants so I sieved some and used it to sow pinches of seeds in 10 modules alongside some pak choi, germinating these in the greenhouse. This was done on 21st July and there are already signs of germination in 7 of the modules as well as some of the pak choi. There is clearly absolutely nothing wrong with my seeds.

I don't mind using recycled compost from last year's plants in the garden and the greenhouse - I do this all the time. But the compost is full of wildlife and I really don't want it in the house. So I have this problem - what do I do for compost for my seeds and seedlings that I keep indoors and for my indoor tomatoes and peppers. Does anyone have any ideas or recommendations for compost that isn't contaminated with weedkiller?

[Nicos]

Good question Pen
Having tried out council compost bought from the tip many moons ago and realising they were full of herbicides affecting my seedlings I really would have thought that someone somewhere would have realised the potential problems with doing this by now.
The aminopyralid herbicide problem about 20 years ago should have been a lesson for everyone….it does make you wonder how rigorous herbicide checks are these days….

[Bren In Pots]

Pen it seems it’s not only the weather thats to blame for failures, I’m looking into making some of my own seed compost.
I’ve found this link that’s interesting.

https://www.kew.org/read-and-watch/m...wn-compost-mix

[Plot70]

There is also a lot of vine weevils about this year. They have taken the roots off quite a few squash plants of mine this year.
If this goes on I will try treating the soil with crawling insect killer before planting.

[rary]

Pen. I have found that wood based compost, (the compost sold by Asda is usually wood based,) seems to be OK for seed sowing, but the compost I use is usually purchased the year before, this gets mixed with washed course sand, I have come across several garden info sites that tells you not to use sand, but I have never had any problems with it, though more and more I am going back to the old way of making seed compost that is river sand, which I call burn sand, mixed with some molehill soil, I know not everyone can access any of these but sieved garden soil and course sand does the same, I am in the fortunate position of having an old air fryer which is great for sterilising both soil and sand, so I would recommend having a look through something like free cycle? where something like that could be picked up, I have used both soil and burn sand without it being sterilised in hanging baskets and sadly some weeds are produced, so really needs heat treated, actually you could try sowing seeds into the course sand itself to see how it does, I recommend it's use for rooting cuttings so it should work for seeds

[mrsbusy]

Hi Penellype.I sympathise - I had lots of problems last year with potted toms which I put down to MPC
This year I have had much better results which I put down to a combo of JI 2 and Sylvagrow sustainable MPC which states on the bag no green waste. So for seeds I use just the JI 2 with plenty of pearlite and once germinated and ready for potting on 50/50 ji2and the
Sylva plus vermiculite
I have used last year's MPC mixed with top soil 50/50 + BFB for the big 30l potato pots and the spuds seem fine so far. I don't want to use just topsoil - too heavy

[ameno]

I think it's actually very unlikely to be weedkiller contamination. The persistent weedkillers which green waste compost can potentially be contaminated with produce very distinctive symptoms, especially in very sensitive plants like peas and beans. They don't cause failed germination or plant death (except in very high concentrations, higher than it would be possible to find in contaminated compost), rather they cause distinctive cupped leaves, distorted growth, and stunting.

That's not to say the compost isn't to blame, though - by the sounds of it, it probably is - it just means that the reason is something other than weedkiller.
Bad water holding is a possibility (either too much or too little), but I think the most likely problem is that the compost has too high a salt level, and this is burning the plant roots. This is a recurring problem with certain composts, especially when they reformulate them, and is caused by the adding too much fertiliser.

I recommend using Melcourt Sylvagrow. It's a little more costly, but it's always been very reliable for me, and is usually a Best Buy.
Because of it's expense, I only use it as a potting compost for seeds and young plants. For containers I make my own mix from horse manure, soil, and used compost, mixed with poultry manure and slow release fertiliser pellets.

[Penellype]

Thanks for all the replies. I have no issues at all with compost for containers and seed sowing in the greenhouse as I reuse old compost or home made for those, with bfb added when needed. My big issue is with using that in the house, because I draw the line at importing worms, ants, millipedes, centipedes etc. The sciarid flies that come with bought compost are quite enough!

Sand, soil and John Innes are out of the question - I am in my 60s and I can't lift bags of those and I have nobody to help me. I will see if I can find a source of Melcourt Sylvagrow in this area as that sounds a good choice.

I agree about the vine weevils - my pea plants in the allotment tunnel have the characteristic notched leaf edges caused by adult vine weevils, and one of the cucumber plants in there died suddenly and when removed had almost no roots. I intend to treat the soil with nematodes later in the year (the nematodes don't kill the adults). The vine weevils aren't the problem with the germination though.

I didn't know about the salt issue. That could explain it, its more likely than waterlogging and it definitely isn't drying out - the compost was damp when I dug out the peas to see what had happened after there was no growth visible for 2 weeks (peas with roots before planting). The peas were in exactly the same state as they had been when planted, except that the roots had gone slightly brown. They weren't noticeably rotted, just clearly dead.

[Nicos]

Pen- my MIL who was in her 80s bought herself a porters trolley specifically for bags of compost. The staff at the garden centre would put then I. Her car ( back seat was the easiest) then when at home she’d drag it out, gravity assisted, onto the porters trolley which she’d pull into the garden…and it would stay there until she’d used enough to make it light enough to drag it off.

Just thought I’d share that info for anyone else who might struggle with the weight of the bags.

[Sweet savory]

I also use melcourt sylvagrow for seeds and seedlings. The cheaper peat free was causing a lot of problems earlier this year with yellowing to young plants and sporadic germination. So I bit the bullet and went upmarket. I repotted the affected plants and within 2 weeks they were back to normal growth and germination is no longer a problem so for me the extra expense is well justified.

[burnie]

Only two composts I buy now, Coir base with added clay and John Innes loam based, all the others are proving to be very poor quality, full of hoouse hold waste which as many have said seems to contain contaminants.

[Penellype]

Pen- my MIL who was in her 80s bought herself a porters trolley specifically for bags of compost. The staff at the garden centre would put then I. Her car ( back seat was the easiest) then when at home she’d drag it out, gravity assisted, onto the porters trolley which she’d pull into the garden…and it would stay there until she’d used enough to make it light enough to drag it off.

Just thought I’d share that info for anyone else who might struggle with the weight of the bags.

Thanks, that's interesting. My drive is gravel though, which makes using anything heavy with wheels rather hard work. I'm ok with bags of compost as long as I stick to the 50-60 litre bags, but the heavy stuff defeats me.

[rary]

Pen re the vine weevil, one of my lilies was showing signs of being attacked by Vine weevil notched leaves and all the leaves drooping, I ordered nematodes but it was a three week delivery date, so I drenched the roots with a garlic solution, and by the time the nematodes arrived the lily hadn't deteriorated and none of the others showed any signs of being attacked by them, I kept the nematodes in the fridge up till a couple of days before the use by date, with no further signs of vine weevil, I finally added the nematodes as directed just to use them up, not sure if a garlic drench would work with peas but you will never know till you try, the lily is now in flower and looking fine

[Penellype]

Pen re the vine weevil, one of my lilies was showing signs of being attacked by Vine weevil notched leaves and all the leaves drooping, I ordered nematodes but it was a three week delivery date, so I drenched the roots with a garlic solution, and by the time the nematodes arrived the lily hadn't deteriorated and none of the others showed any signs of being attacked by them, I kept the nematodes in the fridge up till a couple of days before the use by date, with no further signs of vine weevil, I finally added the nematodes as directed just to use them up, not sure if a garlic drench would work with peas but you will never know till you try, the lily is now in flower and looking fine

Interesting. I have some garlic granules so I might give that a go, thanks.