New compost?

Hi, I know this is probably a really stupid question but when I'm replanting my window boxes and containers this year do I need to empty out last year's compost and put new compost in, or can I use the same compost that is already in? Thanks.

 

All the fertiliser and goodness from the original compost will have gone. However, all the goodness from any new compost will be used up in a month or so ... and you'll have then have to feed - presumably you feed anyway?

Other issue is that new compost will be sterile, old compost may have diseases carrying over from last year.

Personally I reuse last years, mix in long term / slow release fertiliser granules, and I mix water retaining gel into the bottom half (ONLY!!) of the container's compost. (I found mixing it into the top just brought it to the surface and either the birds ate it! or it looked a mess, and anyway the roots need the moisture lower down ...)

 

Hi Kristen, thanks for replying. Feeding, er, no haven't done that before, crikey there is so much to learn. Does that need to be done monthly? That's helpful advice about reusing last years soil, sounds easier than getting in new compost. Should I be tipping it out first and cleaning the pots?

 

Well I reckon if you didn't feed them last year, and you do feed them this year, you'll be well chuffed with the results!

By the time you have bought long-life fertiliser granules and water retaining gel, and assuming you have only a couple of tubs and no other pots and urns etc. in your garden, then you may find buying a bag of new compost (choose one that already has long life fertiliser and water retaining gel) may well be cheaper, and will give you a squeaky-clean start - a whole pot of the fertiliser granules and water gel stuff will keep for future years though.

I have to say that the conventional wisdom is to replace the compost. I've been gardening for a long time, so my cavalier approach is based on me having some knowledge to spot if things are not right and hopefully also to sort them out. I'd hate my bad habits to give you a total failure of your tubs this year!!

If you decide to replace the soil by all means wash out the tubs - you are aiming for a disease free start. If you are keeping the old compost there isn't much point as any disease will be in the soil too.

Of course if the outside of the tubs looks mucky that's worth a clean.

I think the chances of disease in your tubs is close to ziltch - unless you are growing things that are prone to disease and those diseases persisting; I wouldn't grow Tomatoes in the same soil twice, for example, but my tubs of Fuchsias, Petunias, Lobelia etc get the same soil every year.

If you've just got a couple of tubs then Baby Bio is most likely to be the easiest feed to use - its designed and packaged in a small bottle for use in small doses - and will work wonders on your house plants too. I tend to feed my tubs with Tomato fertiliser (such as Tomarite) because I use lots of it and its quite strong (there is not much soil in a tub for the plants to live off)

 

I am also using new compost with built in feed this season so lets see the end result as I always feed my plants in containers and baskets and my shrubs in ground.

 

Well, I have got quite a few pots- last year was the first time I'd had a garden so I just chucked things in beds and pots and hoped for the best and all seemed to turn out ok, but this year I want to get a bit more knowledgeable about what I'm doing hence joining this forum. Thanks for all the advice, I'll have a think. Can I ask another very stupid question- what do you do with all the old compost that you chuck out of the pots- add it to flower beds?

 

No I take to my local skip to recyle as I have bark in most of my borders and shrubs in gravel low maintaince and containers and raised beds.

 

"what do you do with all the old compost that you chuck out of the pots- add it to flower beds?"

yes, or I put it in my compost heap - so it gets mixed in with everything else.

I'm very careful about compost from pots that grew, for example, Tomatoes so that it gets into my crop rotation correctly. Tomatoes are the same family as Potatoes - so I put the old pot compost on the bed which has JUST had Potatoes, and then I don't plant Potatoes in that bed for another four years.

For anything that came out of pots which just had annuals, bulbs, summer bedding plants, that type of thing, I use it wherever the soil would benefit, or chuck in the in the compost heap. I paid plenty of money for the compost bags, I'm not giving it back to the council for free!

 

Probably doesn't apply to many people here, but I add old compost to the chickens dust bathing areas - they love it. If I have a pot of something that has died or similar (think basil or coriander that's gone past its best) the pot goes into their run and they will spend hours poking through it for roots and bits of stuff!

Everyone should have a couple of chickens - great disposal units