David23
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Posts: 24
Joined: Wed Oct 05, 2011 5:51 am
Location: England, Midlands

How good is multi-purpose at the end of the day ?

I have been on other forums and asked about multi-purpose compost. There is quite a dim view of it with keen amateurs. I once potted up with it this in around June time and then tried to carry my 9cm pots(perennials) through winter with this. I found that the compost was possibly to old and flat to get a good result.

This time I have potted them up in mid august from already having had a good root system from 9 cm pot and re-potting up again fresh into new pots. So basically good roots into a fresh multi-P mix.

I wondered how well they would perform 'on average' given most perform reasonably in summer. This time I have added vermiculite with the peat based multi-purpose. In a thread you talked about this in August 2009.

I was thinking about adding a top dress of loam so the peat does not go to flat over winter and am hoping vermiculite will help drainage.

Also one more question. Many people say that the organic matter humus of peat holds on to water well. I understand this but why does it dry out quicker than a loam mix if this is the case in summer ?

I would prefer if a scientific answer did not get to scientific as it can be confusing I find. It is useful though to explain things.

It should be interesting to hear the views on peat/perlite and overwintering.

Then also water holding with vermiculite added to multi P in winter.

Don't forget loam could be added as a top dressing now.

Thanks very much.

David.

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rainbowgardener
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Joined: Sun Feb 15, 2009 6:04 pm
Location: TN/GA 7b

We don't always speak the same version of English on opposite sides of the pond. I take it you are using compost to mean what I would call potting soil or potting mix? Here compost is the resulting product from a compost pile, rotted down kitchen scraps, leaves, weeds etc, without additives.

But potting mix is usually peat based with probably other organic matter and vermiculite and typically here has Miracle Gro or other fertilizers added. Peat does hold on to water well AND once it totally dries out, it can be difficult to wet again, water tends to run right off/over it, without sinking in, like water over a dry sponge.

I over winter all kinds of plants, including shrubs and trees as well as flowering plants, house plants, and herbs in (general multi-purpose) potting mix. It does tend to lose volume over time. But for the stuff that stays in pots (as opposed to going in the ground for the summer) all I do is once a year dump all the soil from the pots into a wheelbarrow, add an equal quantity of fresh potting mix, stir it all up and repot. I don't add topsoil (loam) or anything else, but the potting mix does have fertilizer in it. I know it is not what everyone would recommend, but it works for me. I have a lovely angel trumpet tree that I started from seed a few years ago, that currently is about 4 feet tall and has its second flush of blooms for the season. It lives all the time in a container with potting soil, outdoors in growing season and will come in soon.

David23
Full Member
Posts: 24
Joined: Wed Oct 05, 2011 5:51 am
Location: England, Midlands

That sounds good then. What we call mult-purpose mix in the Uk is an all round potting mix for seeds and potting on. A good peat based one has 60- 70 % peat and the rest sand. It does have 6 weeks worth of food added in. A 'potting on mix' in the Uk , a different mix , has more nutrients and I think a slightly different mixture , a specialist mix for potting on instead. From what I have understood in the Uk multi-purpose mix is a slightly finer consistency 'also' using for seed or cutting. It is sufficiently bulky though as similar to a potting mixture but 'not quite'. Hence being multi purpose.

This means by winter from potting mid-august it will have less food in a multi purpose mix. Having said that I could be wrong since watering is less in the Autumn and winter. To make sure I thought a top dressing of loam adds more nutrients. Although this is only one way of doing it since potting multi P mix could be used for a top dressing as fresh.

Is vermiculite helpful for stopping compost getting to flat. I know it holds water or lets go of the water when dry or wet conditions are experienced by the plant even in winter.

Its just a thing I am checking out to make sure I am right. Although many varied answers could be shown to me of course on this forum.

Thanks rainbow gardener.



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