How compact should your soil or potting mix be.

[davidwood]

I have searched everywhere on the Internet for the answer and i cant find out. I have had many problems and i think its because i have had the mix much to loose.
When i first bought Hibiscus of HVH i had only been gardening 3 months so no experience of what is right or wrong.When my cv's arrived the soil was very loose [to stupid to think after 3 weeks in transit and being banged about that maybe it should not be loose] and i have kept them like that ever since.
I suppose a good test of how compact it is would be how quick the water dissipates of the surface,up until now mine poured straight through.
So how long should it take? or is there another way to make sure you can check you have it compacted correctly.

[Darkhorse]

David,

   I would think the soil mix being too loose would be better than the soil mix being too compact.  Patting down the soil too much could contribute to poor drainage, and the roots may not be able to make their way through it properly.  I'm sure someone else will have something to add but this is my 2 cents in the middle of the night.   

Jordan

[Charlie]

Jordan, you're right. The easiest way to kill a hibiscus is to grow it in heavy, compacted soil. All plants need a mixture or air and water in the soil they are growing in. If you compact the soil too much you drive out the air. Even in hydroponic growing, where the roots grow directly in water, the water is aerated by bubblers or other mechanical means so that it is not depleted of oxygen. If the soil is too compacted it prevents the necessary movement of water, nutrients, and even root growth through the mix.

Potting mix is a little different than dirt. There is a different dynamic going on in a pot as compared to what is happening in the ground. Potting mix is there for 2 main reasons - to give the roots a place and substance to anchor to so the the plant remains upright, and second to hold sufficient water and nutrients so that the plant can "drink" them in through the roots. The ability of potting mix and the individual ingredients in it to absorb and hold nutrients, and then to give them up to the roots as needed is actually measurable as something called cation exchange capacity.

So David, the shorter answer to your question is that the soil mix in your pots needs to be compacted enough to provide support for the roots and the plant in wind and rain, but should not be compacted more than is necessary for that purpose. The HVH mix is very porous and naturally resists over-compacting. You do not have to work at it to provide the needed structure, just tamp it down as much as the plant needs to be well anchored and then don't worry about it after that. This mix is intended for wet climates or daily watering (in pots with good drainage) and won't compact too much so go ahead and firm it up as needed.

I'm still unclear about the problems you see. I suspect they are mostly related to the ultra-high temperatures in your area, but am not sure. It can take time for young hibiscus to adapt to a new environment and to grow up into stronger plants that can take more stressful conditions in stride. They need stable conditions to do that well, so once you find something that works it is best to stick with it so the hibiscus can adapt properly.

Charlie

[Pachrian]

I read somewhere, and of course I can't find it now, that a good method is what they called the 'earthquake method'. Basically you pick up you pot, shake it and tap it on the ground as you fill it. It works for me. 

[davidwood]

Charles i actually now know what was wrong,i just don't understand why.I sorry i don't know the exact terminology but the roots weren't grabbing the soil mix.Maybe i did have it to loose but i could after 1 year   just pull the plant with little ease right out of the pot.I am lucky they haven't all died. So that's why i have gotten rid of this coco coir as i cant think of what else it could be.

On reflection and trust me i have given this a lot of thought; maybe the coco i buy here is not to the same standard you  buy. I have since seen other coco and it was no where near as dusty as the stuff i originally bought.

[Charlie]

Coco coir does vary a lot. When it first started being used in horticulture there were problems with quality. Eventually some of the bigger suppliers of potting mix got involved and took the guess work out since they did the quality control work and what they sold was reliable. It's too bad you can't take advantage of the local supply but not that surprising since the coir is really the waste left over after coconut shells are processed for other purposes. No easy answers here.

Charlie