[Luiska]

I introduced this query in a different thread without thinking, so I'll start afresh.

I've never used these cardboard pots before - had my trusty faves when gardening in Finland and used them again and again. But these seemed like a great idea when I encountered them here and I've used them quite generously this first season in England - rather cheap from poundland. Except yesterday, when putting some tomatoes in grow bags from 4 inch pots which I'd put the put the small cardboard pots into about 4 weeks ago, I noticed that the roots had not gone through the biodegradable material. This is a bit of a blow. I peeled it back with some difficulty but I don't fancy doing that for everything.

I'm assuming the roots must eventually go through the membrane or they wouldn't still be on the market, but what do other people think about them? Do they slow root development and spread?

[AlaninCarlisle]

Yes, I use them every spring for all kinds of beans, tomatoes, cucumber, courgettes and stuff. I find they are a quick and easy way of starting stuff in the propagator or greenhouse and then moving on to either large pots or open ground with minimum root disturbance. The roots will only penetrate the fibre if there is moisture on the other side, so keep them damp if this is a concern with you

[JayG]

The biodegradable pots I've used in the past were made from compressed peat I believe (although it did look a bit like cardboard.)

I'm not a fan - it can be quite difficult for delicate roots to pass through them, especially if they are on the dry side, and when planting them out you have to make sure the tops are buried to avoid the moisture 'wicking' away from the pot which of course makes the problem worse.

Feeling the need to partially break open each pot when planting out somewhat defeats the object of using biodegradable pots in the first place.

I use home made paper pots these days, which apart from being free, are much less likely to restrict root growth - you still need to make sure the tops are buried when planting out, although they are relatively easy to tear off if they are exposed.

[AnneB]

I am in complete agreement with JayG.   The biodegradeable ones don't allow roots to go through without assistance.  Don't bother with them now.  I use paper pots for sweetcorn, but aside from that I just use yogurt pots with a whole in the bottom made by a heated skewer.  Round here I buy Longley Farm yogurts and they are an ideal size for sowing tomatoes, peppers etc.  Other than that I ordinary plastic pots or cell trays, mostly reusing the supply I get from other garden purchases. 

[AlaninCarlisle]

I've been successfully using fibre pots for about ten years, almost since they first appeared on the shelves of B and Q. There are two key things to remember when using them:
Don't let any part of the pot appear above ground as it will quickly dry out
Keep very moist at all times before planting out as the fibre acts like blotting paper and then when dry becomes a barrier to root penetration

One further time-saving tip when planting out. One of those conical/tubular bulb planting gizmos gives you a hole of exactly the right diameter to make a snug fit and you can plant a couple of dozen potted plants, neatly and accurately within two or three minutes

[mumofstig]

I'm another fan of paper pots, rather than the cardboard type.

[Luiska]

This place is a godsend. I didn't know that I had to make sure the upper rim was buried; I'm almost certain that is at least part of the problem - though I still don't feel very confident about them anymore.

But I have just looked up how to make pots from newspaper, which really seems like a great idea.

And I read somewhere, just before starting on the plot, that now was the time to start collecting used loo rolls and I have been doing that without having the faintest idea why - such a twit I am - but now I know about that too and really regret my Greek gigante beans rammed into pots that clearly won't take their rooting preferences into account. I won't sleep peacefully until I have them planted out - and being eaten by slugs. I never encountered a slug in Finland; I think the winters are too cold. There's a lot to learn.

[ARPoet]

I tried the fibre pots years ago... were they called Jiffy Pots?
I thought they were rather expensive for what they were. I then went to making newspaper pots when i had the lottie, but when i was packing up the lottie i got given a box full of used 3 inch used plastic pots. I use them now plus loo roll centres for peas and beans.
I am not a fan of spending money when i can help it.

[Luiska]

I think this shot of a tray of sweet corn seedlings just before planting out yesterday says everything that needs to be said about the pros and cons of biodegradable v. plastic pots. This is a red corn, and the stem is supposed to be red - and the fact that the leaves of the bio-pot plants are also reddish is probably not a great cause for concern. But look at the difference in size and general health! Maybe bio-pots need more water or something, but this lot shared a tray for 3 weeks and got exactly the same treatment, so it will be plastic for me in future.

[al78]

I never encountered a slug in Finland; I think the winters are too cold. There's a lot to learn.

Britain is the slug capital of the world, thanks to our relatively mild, wet winters, and cool(ish) damp summers.

http://www.slugoff.co.uk/slug-facts/so-many-slugs

In my area, there has been more rain yesterday than during the whole of the year so far. I have brassicas planted out so am expecting lots of slug damage when I get to the plot this evening, despite my best efforts with nematodes and copper rings. The organic slug pellets will have to come out. At least I have grown twice as many brassicas as I need, so have got plenty to replace ravaged plants at the moment.

[Luiska]

That's something to look forward to this afternoon.

[New shoot]

I think this shot of a tray of sweet corn seedlings just before planting out yesterday says everything that needs to be said about the pros and cons of biodegradable v. plastic pots. This is a red corn, and the stem is supposed to be red - and the fact that the leaves of the bio-pot plants are also reddish is probably not a great cause for concern. But look at the difference in size and general health! Maybe bio-pots need more water or something, but this lot shared a tray for 3 weeks and got exactly the same treatment, so it will be plastic for me in future.

I don't usually buy the compressed peat/cardboard pots, but I was given a couple of huge packs, so have corn and beans in some.  As Alan says,  they do need to be kept damp, so mine are sitting in a gravel tray so I can keep a thin layer of water in the base.

With paper or these bought bio pots, you have to remember that the roots pass through them.  If you let them dry out, the roots suffer.   I have planted stuff out before that has loads of roots sticking through the pots, so if your corn doesn't have these external roots, that would indicate a problem.

In plastic pots the roots tend to circle, so its swings and roundabouts as to the pros and cons of each.  They just need slightly different management.  A seed tray with drainage holes is fine for plastic pots as they don't dry out so fast.  One without holes and slightly more water is better for the bio pots 

[Luiska]

This tray had no holes. But what you say about the roots is spot on: they had come through the bio pots and were straggling around (and a gorgeous variegated red and white), whereas they had circled the plastic pots a bit (and all white). I'll be interested to watch future development.