Houseplants forum: Tropical houseplants - water before repotting or not?

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London
dryrot
Jul 14, 2017 7:17 AM CST
I've put off repotting for a long time but now I definitely need to repot my peace lily, dragon tree and areca palm. Their leaves are starting to lose their green colour just due to lack of nutrients and liquid feed is only slightly helping. They also have roots coming out of the bottom of the pots and all that.

Currently their soil is very dry though. Should I water them first and then wait a few days before repotting, or would repotting into moist soil be okay?

And is it okay to repot in summer? (UK)
Name: Will Creed
NYC
Professional indoor plant consultan
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WillC
Jul 14, 2017 1:51 PM CST
As you may know from some of my other postings here, I am not a big fan of unnecessary repotting. Loss of color is rarely caused by being potbound. Plant food should adequately replace nutrients if you use a complete fertilizer and the soil pH is in the 6.0 to 6.8 range. It is quite normal for some roots to wander out of the drain hole and is not necessarily an indication that repotting is necessary.

A more reliable indicator of needing a larger pot is when the plant needs more than twice weekly thorough waterings.

If you decide to repot, it is best that the rootball is quite moist before removing it from its pot. The moisture will make it easier to get it out of the pot and will also keep the rootball intact after it is removed from the pot.

Indoor plants can be potted at any time of the year, assuming it is necessary and assuming the plant is healthy.
Will Creed
Horticultural Help, NYC
www.HorticulturalHelp.com
I now have a book available on indoor plant care
London
dryrot
Jul 15, 2017 6:13 PM CST
Hello Will, thanks for the advice

Would you be able to determine if the plant needs potting just based on size? There are some plants I have that definitely need watering more frequently than once per week though I'm not sure if they're at twice a week.

Name: Ed
Central ,NJ (Zone 6b)
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herrwood
Jul 15, 2017 7:36 PM CST

I usually pot up when there is too much plant for the pot. Or another way to say it is the pot is full.
I usually water after I depot
but if it's real dry Wills reply makes sense.
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Name: Will Creed
NYC
Professional indoor plant consultan
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WillC
Jul 16, 2017 3:01 PM CST
When a plant "looks" too big for its pot is highly subjective and not a reliable way to determine repotting. The purpose of the pot is to hold enough soil so that it can absorb and provide water to the roots for several days or longer. That soil also must be porous enough and allowed to dry out sufficiently so that the roots get oxygen at least weekly. Without getting into too much detail, it is the ratio of the roots to the soil volume that matters. Professional growers know that the ideal ratio is about 80% roots to 20% soil. But there is no way for the layperson to tell that accurately by appearance. However, experience shows that if there is enough soil to absorb adequate moisture for the roots for several days or more, then repotting is not necessary. Hence my rule of thumb of more than twice weekly watering before repotting.
Will Creed
Horticultural Help, NYC
www.HorticulturalHelp.com
I now have a book available on indoor plant care
London
dryrot
Jul 17, 2017 7:53 AM CST
Hey Will
So I checked the moisture for all the plants with a meter after 3 days and they seemed dry, so I decided to repot them
I haven't repotted a plant in a long time and so I threw together some John Innes No. 2 potting soil (7 parts Loam, 3 Peat, 2 Sand) perlite and bark. I feel like potting soils with sand never let water drain fast enough. I've even bought cactus-specific potting soils with a lot of sand that when watered turn into a sludge that only releases water very slowly. Perlite helps a lot with drainage but I'm worried I now don't have enough water retention.
I think I put in way too much perlite though, probably because most of my plants are succulents and I'm not used to potting anything else. It was getting close to about half perlite half potting soil, maybe 40%. I've already potted them. According to Should I fix the issue tomorrow? If they don't have enough actual soil in there I'll run into the same issue of having to water too often
[Last edited by dryrot - Jul 17, 2017 8:04 AM (+)]
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Name: Will Creed
NYC
Professional indoor plant consultan
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WillC
Jul 17, 2017 7:11 PM CST
Moisture meters are notoriously inaccurate as they vary with type of soil used, and the mineral content of the water and soil used. Frankly, it seems very unlikely that all of your plants would now be drying out together after three days.

Your concerns about potting mixes highlight just one of the many problems that can occur when repotting is done. You didn't mention pot size or whether the rootballs remained intact when you repotted. That is why I don't recommend repotting unnecessarily because most folks don't know how to do it properly and end up doing more harm than good. I hope you are the exception.

You are right about sand. It has the benefit of adding weight, but the particles are so fine that it tends to not allow enough space between the particles for air to penetrate. The result is root suffocation. Most potting mixes avoid sand. Perlite is a better way to create porosity, but 20 to 25% is appropriate for most non-succulents.

Disturbing the roots yet again may not be such a good idea. The new potting mix may be retaining more water than you realize, particularly if the pot is larger. Don't rely on the meter to tell you.
Will Creed
Horticultural Help, NYC
www.HorticulturalHelp.com
I now have a book available on indoor plant care
[Last edited by WillC - Jul 17, 2017 7:15 PM (+)]
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London
dryrot
Jul 18, 2017 3:31 AM CST
Thanks for the advice again, I'll be more careful next time.
How do you measure moisture? I mean, when the plant is dry at the top there might still be a bunch of moisture at the bottom or somewhere in the middle.

I was aiming to replace the soil so I put two of the plants in their original pots but with more soil (they had a bunch of empty space at the top because the soil sunk over time). A fourth plant (Anthurium) I put in a pot where I was able to add maybe one more inch of soil around the rootball.

uhh I disturbed the rootballs a bunch, even trimmed them a bit

The current pots the plants are in aren't their original pots either though, I've repotted them before and they never had any problems for years since then until now. Even if I have damaged the roots, I don't think it should be a permanent problem. I'm not trying to get the plants to grow any larger because they're already big enough (except the dragon tree maybe).

I haven't repotted the dragon tree yet because there weren't any pots slightly larger than its old one so I'll wait until I get a new one for that. However there was a whole layer of thick roots at the bottom of the pot instead of roots. I could avoid making the same mistakes with that if I do or don't repot it.
[Last edited by dryrot - Jul 18, 2017 3:41 AM (+)]
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Name: tarev
San Joaquin County, CA (Zone 9b)
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tarev
Jul 18, 2017 9:39 AM CST
Hello dryrot, I just use skewer method to check the moisture of my indoor container plants, stick it into the soil, if it comes out wet, delay watering a day or so. Or if the plant container is small, compare the weight before and after watering. It is heavier when it is watered, then eventually goes lighter as it dries out. You can also place a big rock on top of the soil. If you lift that rock and the soil below still looks wet, delay watering.

For my indoor plants, I prefer to repot my plants during mid-Spring. Even though they are indoors, the light levels changes too. During the cooler months even indoors, they also slow down in growing, and scale down watering too. Once the warmer season starts to come around in Spring, then I do my repot. I guess it is a matter of preference, but I find it better that way, temps starting to warm up and stabilize for the plant, unlike in winter, even if there is heater indoors, it is too dry and they are not in full growing vigor. Better to wait for Spring.

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