Question for Giga (et al) re hydroponics, sorta

[zxcvbob]

I've pulled up some milkweed vine suckers coming up in my neighbor's yard from the seedlings I planted on the fence last year.  (I had no idea the rhizomes spread far underground)  They pull up easily with a nice piece of taproot with just one or two short side rootlets.  I put one in a beer bottle of water to try to get it to grow roots so I can grow it in a pot to feed Wife's monarch caterpillars.  

That was 3 days ago, and no new roots yet but the top has mostly recovered and is actually showing a little bit of growth.  Should I add a tiny bit of Miracle Grow to the water to give it some nutrients?  It may be there a while.

[zxcvbob]

No takers?    

I did some searching today.  I still don't know if plain water is okay or if the plant needs some nutrients, but water drawn from an aquarium is probably better than highly-diluted MiracleGro.  And the aquarium needs cleaning...

[RoadKingLarry]

Give it a week or so, it takes a while for the roots to be big enough to see. If you want to try again see if you can find some rooting hormone and try rooting them in damp seed starter soil.

[zxcvbob]

I have some rooting hormone powder; I didn't use it because there's already a tap root, it just doesn't have any side roots yet.

The plant seems happy enough in the plain water.  I will leave it like that for now, then when it's time to change the water maybe switch to fishwater.  If I kill this one, there are plenty more trying to take over her yard (oops)

[GigaBuist]

If you've already got a taproot but want to see more growth out of it I doubt rooting hormone is going to help.  Granted, propagation isn't really my jam, but I don't recall us ever using that except on things that don't have a root at all. 

It probably needs some phosphorous to push out new roots.  Fertilizers can (and should) contain a bunch of micro nutrients but the big macro nutrients are nitrogen, phosphorous, and potassium, or NPK.  That's what the three numbers on fertilizers are about. Nitrogen to promote vegetative (green stuff) growth, phosphorous to grow roots and blooms, and potassium for moving around stuff, mostly water, which helps them deal with stressful situations or setting fruit.

If you've got a water soluble fertilizer like all purpose Miracle Gro around I'd probably mix that in at 1/4 of the label rate and set the plant in that, see if it roots. It might burn the snot out of it.  If so try cutting it in half.  I'm not sure how to dose that stuff off the top of my head. 

[zxcvbob]

It looks like a taproot, broken off at the bottom where it separated from the rhizome.  The one little side rootlet looks bigger today, and the plant is putting out new top growth.  I think I'm worrying too much; it would probably take a strong herbicide to kill this thing.   

[Firethorn]

It looks like a taproot, broken off at the bottom where it separated from the rhizome.  The one little side rootlet looks bigger today, and the plant is putting out new top growth.  I think I'm worrying too much; it would probably take a strong herbicide to kill this thing.   

One thing I remember reading is that plants grow what they need first. 

If it's getting enough nutrients from the water already* from its taproot, why would it grow more root structure?  That's fine, it can grow more topside!

It's one of the reasons why I remember reading that you should water new trees away from the trunk - in order to encourage root growth away from the trunk to give it more stability.

*I know you're not using fertilized water, but it mostly just needs trace minerals and such.