511 mix for begonias?

Hummingbird597(6)July 2, 2014

I am getting ready to repot some begonias. I posted a couple months ago for help ID'ing a new begonia, which turned out to be don miller. True to what I have read about it, it came with a free bonus of powdery mildew, which spread to my 'Audrey Brenda' and 'Sophie Cecile'. Right as I was getting that under control I had a bad fungus gnat outbreak. I am getting that under control but I think I need to get them in a different mix - currently they are in miracle grow moisture control with added perlite. I was thinking 511 would be a good option for less peat, good water retention but also good drainage.
1) is 511 a good idea, or would anyone recommend a different recipe?
2) should I add the lime, or would that be too alkaline for begonias?
3) I usually feed with Schultz plant food mixed half strength at every watering (sometimes every other) would it need any thing else supplemented?

I have several cuttings rooting currently just in case ;)

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Mildew is all around you. Think of cool, dank basements and bathrooms where mildew is usually present and all kinds of products for combatting mildew are on your grocery store aisles. In the great outdoors it often attacks many plants besides begonias - dogwoods, crepe myrtles, phlox to name a few. But being knowledgeable about mildew helps a person to recognize it and be prepared to fight it.

Give your 511 a try and get back with us on how it works out for you. I use Miracle Gro and am fairly happy with it - no mixing - yay! I usually pick up the extra large bags at HD for less than $15. Also Fine Gardening Magazine gave it the best value in their latest magazine of other commercial mixes they reviewed.

A lot of begonias in the wild are found around cave entrances and most caves have a lot of limestone deposits so I don't think it will hurt begonias to be more alkaline but why add it if you don't have to? I've seen begonias in Belize, Guatemala, and the Yucatan living on limestone rocks without human intervention.

The general rule of thumb on fertilizing begonias is slow release and/or a weekly weakly water soluble mix. I kind of quit using water soluble indoors in winter. I've found that mature begonias can take a little stronger fertilizer such as Shake And Feed - not sure if it is a slow release but the results are fairly quick for greening up a pale looking begonia - just a pinch though in small pots. My rajah in a terrarium looked awfully yellow/red so I put a pinch of the above fertilizer in a small open area of the pot and in two weeks the results were very visible.

    Bookmark   July 2, 2014 at 7:37AM
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P.S. I would not use the moisture control as it has the crystal polymers to keep the soil moist longer than the regular potting mix. I no longer amend with perlite either - it may help in starter plants but not necessary for mature plants.

Photo of a few begonias I lined up on the fence. This is just a small part of what I am growing to date.

    Bookmark   July 2, 2014 at 7:42AM
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your pics are always an inspiration!
i grow my 1 large-leaved, rieger and sev juvie non-stops in AV soil/perlite 1:1 - wicked like AVs. they spend half their lives indoors, though. and are under roof on the balcony outdoors. so no raining on them.

This post was edited by petrushka on Wed, Jul 2, 14 at 11:21

    Bookmark   July 2, 2014 at 9:01AM
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Thanks Petrushka. I basically quit growing tuberous since they are treated as annuals here. Love them but can't really grow them well here so I gave up. Maybe that is my problem with them - too wet?

I'm trying 'Santa Cruz' this year in my "begonia wall". There are 3 in there. I think the coleus will win though.

    Bookmark   July 2, 2014 at 12:27PM
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oh, nice!
so you hung the pots on a pellet? sort of like a-frame green-wall? looks great and probably also gives them more air-movement.
i overwintered non-stops (they made tubers!) just as an experiment. usually i'd buy 4" starts, but they don't grow big enough in one year.
so i am hoping for bigger plants this year, since they started with tubers already.
i find they slow down in july-aug when it's really hot. i take them indoors and tuberous too :), to get a/c relief... go ahead, laugh. but then they really start going in sep-oct and all thru november even.

    Bookmark   July 2, 2014 at 12:37PM
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Yes I squeezed the plastic pots into the empty space between the slats of the pallet. If the pallet had been made a little better with squared boards and regular spacing then it would make the job easier to use a standard sized pot. The difficulty is watering them so I often take some out to get the vertical watering needed - especially the Dragon Wings.

It sounds like you have Non-Stops figured out then despite the extra work/care. Maybe I will give them a try again one year.

Here are a few begonias I am growing out from leaf cuttings started last year in full sun earlier today. OUCH!

    Bookmark   July 2, 2014 at 2:44PM
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I/ve cut back on perlite too, Butch, it does tend to 'float' or work upward and I agree, I don't think it is n ecessary for larger plants. I use Sunshine potting mix, it always tests heavily acid as almost every other mix I'v e ever tried does. I saw a comment from the Fafard company that acid soil tends to become more alkaline over time. I wish they had mentioned how long that 'over time' period is.

    Bookmark   July 2, 2014 at 6:37PM
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I guess it took years to come to our conclusions on potting mixes. I used to use Jungle Growth but HD quit carrying it so I switched to Miracle Gro and I think they've changed their mix over time too. They don't use a lot of perlite, quite a bit of bark, and slow release fertilizer. I don't even use that much perlite any more for propagating except succulents or if I can't get to the potting mix, I may take a scoop or two of pure perlite. It does float to the top and often washes out.

Over time I guess most potting mixes will compact and I've read some folks who repot every six months to a year. I guess I'm too cheap, too lazy to do that much labor. I kind of wait until the plant says it can't stand the pot any more before acting or I am starting some new plants.

Here is Drama Queen.

    Bookmark   July 2, 2014 at 9:21PM
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I am using a organic potting soil made by Whitney farms. I believe it is mostly peat with some aged bark, no perlite. I mixed in some shake and feed when potting up. I only grow tuberous. I have quite a few 12" terracotta with three tubers in each. They have done exceptionally well. Water them about every other day. I also have some in glazed clay pots, but they all seem to hold too much moisture. Water maybe once a week, and definitely not much water either. They are not nearly as prosperous.

Any recommendations for a better draining mix for the glazed pots? I was thinking to try adding some Av or succulent mix to improve drainage. My pendula tuberous are in moss baskets with a layer of landscape fabric. I made my own mix for them of: 2 parts cheap potting soil ( lots of wood shavings) 1 part composted steer manure, and 1 part sand. Also shake and feed mixed in. They have done great, water them every other day.

From what I have read, exhibition growers advocate for a John Innes mix which is mostly coarse loam, some sand, and aged manure.

    Bookmark   July 15, 2014 at 1:06PM
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