Daylilies forum: Best potting soil for transplants?

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Name: Sue
Vermont (Zone 5a)
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SueVT
Feb 7, 2019 1:41 PM CST
Hi,
I am in the process of repotting over 400 seelings into larger pots (BJ's 16 oz cups). I have gone through several large bags of potting soil, and some of them have been better than others! I don't think I have found the holy grail tho.

Miracle Gro had moisture control stuff in it that keeps it dry-feeling, but it did have some fertilizer. Black Gold seedling mix is too fine-grained for the second potting, IMO, because I think it will fall apart when I go to plant outdoors, breaking the roots. The Black Gold Organic mix has really annoying, huge chunks of wood in it, like from the chipper in Fargo. Also no fertilizer.

The best one so far has been BX Pro-Mix with mycorrhizae (say that ten times fast). Very dry initially, so I have been mixing in some water with Miracle Gro before use. I also have been adding a quarter teaspoon of Nutricote just below the surface, for ongoing feeding.

Any thoughts on this? I am new to this, and liable to make big mistakes! Thank You!
[Last edited by SueVT - Feb 7, 2019 2:01 PM (+)]
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Name: Ken
East S.F. Bay Area (Zone 9a)
Region: California
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CaliFlowers
Feb 7, 2019 4:47 PM CST
Good questions, and with the general state of potting soils today, you're wise to be concerned.

Most of the ones you mentioned will hold too much water for me, I like to lighten those with some additional perlite.

The BX is already light enough, and is "clean", but is mostly finely ground peat, and will eventually pack down and be rather wet all of the time, excluding air from the roots. Daylilies don't generally mind this too much though. A lot of strong light will keep the seedlings healthy.

The big question is what you are asking the mix to do. A large enough seedling in a properly sized pot will be able to take any decent mix, as long as it's watered and fed well. I assume BJ's 16 oz. cups are tall soft drink cups? Like, 6+" high?

How old and big are these seedlings? (diameter at base of leaves, and approx. number of leaves)

Are you plucking them out of community flats, small individual pots or cells, in other words, will they require separation?

Are you planting them singly in the BJ's cups?

How long are they going to be in the cups, and what are you going to do with them after that? Line them out in the garden?

In my experience, if you're exercising reasonable care, up-sizing containers carries very little risk of root damage, and I usually leave as much of the original soil on as possible. It's trickier if seedlings have grown together tightly in community pots, but those plants are big enough to withstand a little damage.
Name: Sue
Vermont (Zone 5a)
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SueVT
Feb 7, 2019 5:13 PM CST
Thank you so much @CaliFlowers! I learned a lot from your post.

I stratified the seeds for 3 weeks in the fridge, in vermiculite dampened with water + a bit of peroxide. If they sprouted before that time, I took out the packet and planted it, each packet to one 3" square seedling pot (trays with 18 square pots). If there were more than 9 seeds, I split it into two pots.

For that initial planting, I used Black Gold seedling mix.

Now, as they are around 7-10" tall, I am dividing them into single plants in the taller cups. I am taking the largest seedlings first to transplant. I have been rinsing the soil of the group pots with water. As I have been doing this for about 3 weeks, I have seen that some of the first ones I transplanted have tripled or quadrupled in size. There is a lot of variation in this, depending on the variety... some of the leaves are a half inch across at this point, or more. I have only lost 3 plants so far.

The reason I have been rinsing out the initial soil is that many years ago, I worked at WR Grace, which was at that time the maker of the Metro Mix line of potting soils. Grace owned two vermiculite mines, and the one in Greensboro was producing the small-grade ore used for Metro Mix.
At that time, I worked in quality control, and in the lab we routinely washed out all previous soil when repotting with MM, seeing excellent results from this process.

I plan to grow the plants in these larger cups until planting out in a new seedling bed in perhaps May or June.

I have seen a couple of fungus gnats, but am spraying with insecticidal soap..... I am wondering if the nematodes (?) I read about online actually work for gnats.

Thank you again! Sue
Name: Sue Petruske
Wisconsin (Zone 5a)
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petruske
Feb 7, 2019 5:32 PM CST
SueVT,
If you are having just a few fungus gnats, water your plants with a mixture of 1/2 cup of hydrogen peroxide (3% kind) to one gallon of water. That should help. I water my seedlings with this mixture from "day one". I've never had problems with any kind of bugs. I grew mine inside from Feb to June watering like this.
Name: Sue
Vermont (Zone 5a)
Image
SueVT
Feb 7, 2019 5:39 PM CST
Thank you @petruske, I will do that! It's very good to know the right amount of peroxide to use!!

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