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Repotting house plants

David explains why house plants need repotting, which size of pot to repot your plants into, and the best compost to use.
From time to time, you’ll find that your plants need repotting and generally speaking, I try and check my plants at least once a year to make sure that they’re not pop bound and they’ve got enough room to develop a good root system, but also that compost is remaining open in its structure. Now, if we look at this plant, this is an asparagus that’s been in this pot for about a year, in this pot cover, and it’s been regularly watered. And the compost level, if you look here, has actually sunk. So this original plant that I bought in its compost, the compost level has sunk right down.
And you can see that the plant is looking for some more room to develop because it’s sent roots out of the bottom of the pot. And if we knock the plant out of the pot, remember to water the plant first before you try to do this so that the roots come out easily. If we knock that plant out of the pot, you can see that the roots are going round and round in the bottom of the compost, particularly in this case looking for more moisture. But the compost itself, particularly at the top, has started to break down. The structure of that compost at the top has really deteriorated. It’s very dense.
It’s still fibrous, but it hasn’t got very much aeration in it. And that plant is suffering a little bit because of that. It’s sending its roots down to the bottom of the pot looking for air because it can’t find any up here. So this is ideally the time as soon as those roots pop out of the bottom of the pot to knock it out, have a look and see if it needs repotting. And I think this could do with a new pot. So if we look at the size of the pot that this plant was growing in, it’s probably adequate in terms of the size, for the plant to develop of this sort of size.
But I’m actually going to give it a slightly larger pot because I know that this plant will really perform well if it’s given a larger pot. So I’ve got a pot that’s large enough for me to put my finger in all the way round, so just big enough to add some more compost into the bottom here and around the sides, but not an enormous pot where the roots of the plant will just dash out to the edge of the pot and start going round and round again. We want the plant to make use of all this new compost that we’re going to put in here. So don’t pot it into too large a pot all in one go.
So, as I say, this is the sort of order of pot size I’m going to put this plant into. In terms of what compost I’m going to use, I’ve got a mixture of a peat-free compost here, which I prefer using. This is something called Silvaperl compost
available online, but also at some garden centres. And I’m mixing this, equal parts by volume, with coir fibre. And this coir fibre holds the structure of the compost open for longer. So equal parts by volume of Silvaperl and coir fibre, mixed together. And what that produces is quite a fibrous compost, nice and open and free drained. And I know that I’m going to keep this plant in here for a year, perhaps 18 months, tops, before I knock it out, check it again and I might tease some of that compost away and repot it again. But I know that this is going to last this plant long enough in indoors, in growing indoors as a house plant.
So there’s my compost all mixed together there – really lovely and fibrous mixture there. Difficult to press it hard together, it just pings open, which is the sign of a good compost. It maintains its structure. It’s easy to break it up, doesn’t plod together into a great lump. And then I’m going to take my pot and I’m just going to offer it in position again. And I’m aiming to get the finished plant growing at the same level in this new pot as it was in the old pot. And if you’ve never repotted a plant before, then this is quite a useful trick to use, not something that I tend to do a lot of.
But if you put a little bit of compost into the bottom of the new pot and just lightly firm it down, so it’s flat, and then offer the plant in its old pot into position, you can see, still in its pot, you can see where that that finish position is going to be. It wants to be level, this pot needs to be level with the new pot on the outside. So I’ve put a little bit too much in there. You can go back and take a little bit out, out of the pot, and then put it in position and that’s just about right.
You can also use this original pot as a mould to make a hole for your pla nt to go into, and this as a say, if you’ve never reported a plant before, this is a really simple process. So you just leave the plant in its original pot, stand it on the compost at the base of the new pot, and then you just fill in with compost in between the gap between the old pot and the new pot on the outside. Just fill in with that compost all the way around, feed it in gradually and you can see that that’s more or less filled in all the way around.
Then carefully use your fingers to lightly firm between the old pot and the new pot. Firm that compost in position all the way around, feed a little bit more in and keep firming that in as you go.
And this is also a good way of testing that you’ve got the right gap between your old pot and your new pot, that you can just get your fingers in there to firm that compost in place all the way around. A
little bit more just to finish off. And again, firming that in position right to the top or fairly close to the top. And then you can take the old pot, wiggle it a little bit, take the old pot out and you’re left with a mould of the root bowl, a sort of an imprint, if you like, in the new compost, an imprint of this root ball there that then makes it really easy to knock this plant out of that old pot and just insert the root ball straight into that space that’s been left behind. So all you’re doing is just taking the plant out of its pot and just slipping it in place into that preformed hole.
And it sits perfectly in there. And then you just finish off by filling in with a little bit of extra compost around there, lightly firming that in place, getting
it roughly level, tapping the sides of the pot, tapping it on the bench or the tabletop just to get it nice and level. And there’s my plant repotted, and ready to go. I’d need to put this to stand on a slightly larger saucer than was the original, that was under the original pot. Or I might need a larger pot cover because this pot cover is just a little bit too small now for the size of the plant. But this plant will really benefit from that new compost and will grow on really strongly.
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