Hardy Tropicals UK

Quick question. What do the panel believe is the best mulch in terms of protecting the rootstock of plants from the cold?

Gravel/Grit/Shingle (so basically stone) or wood chip/bark (so basically wood)?

I see that there is now a 3rd option and that is rubber (lots of nice colours too).

http://en.wikipedia.org/wiki/Rubber_mulch

Rubber mulch provides several advantages over plant material based mulches. For landscaping and gardening purposes, both nuggets and buffings insulate soil from heat allowing a 2 or 3 degrees F higher soil temperature difference over wood mulches. Rubber mulch is beneficial for soil moisture as rubber is non-porous and does not absorb water on its way through to the soil. It also reduces fungus growth and plant growth, and becomes a weed barrier as weed seeds dehydrate in the mulch before reaching the soil. Neither nuggets nor buffings provide any humus to compacted soil types.

http://www.rubber-mulch.co.uk/playground.php

So, stones, wood or rubber?

Saw this discussed on another forum a while back - advice was strongly against using it, because of toxicity issues.

So, gravel or wood bark/chip?

Which is better for attracting heat to the ground and keeping it there on cold nights?

I've tended to use light coloured gravel, but I wonder if wood keeps the heat in better?

i guess for herbaceous stuff a lot of fibrous woody mulch is best, but for most palms [except Trachies] and Yuccas/Agavaceae etc. dark coloured stone would be best, with the ability to absorb sunlight and relase it at night.

Sad to say - if we have extended cold like we did in December, with daytime temps only hitting -4C, no amount of mulch will retain the heat - it will leak out anyway.

Mulch is great for retaining moisture and suppressing weeds. Seems to me the factors are:

- chipped bark breaks down. So it's great for slowly adding organic material to a heavy soil. I have also found it makes a home for worms - often if you scrape it away, there are lots of worms living under it. Pine bark probably acidifies the soil a bit. Bark chippings mimic the forest floor where bits of dead trees are slowly decomposing - so are a natural choice for understorey plants like ferns.

- stone shouldn't break down - so doesn't need replacing as much. Limestone chippings will slowly leach into the soil, helping to make an acid soil more neutral, or make an neutral soil alkaline. Stone can be very decorative. Stone chippings can go well with the more structural or architectural plants - e.g. palms.

I see that there is now a 3rd option and that is rubber

I can only imagine the smell of it on a hot summer day
Bark breaking down uses nitrogen from the soil so additional fertilizing is recommended. A thick layer of the stuff is a very good winter protection for roots but it should be removed in spring otherwise soil underneath warms up much slower which is no good.
Stone depends on the color gathers more or less heat during the day and gives it off at night. White stone reflects light so soil does not heat up very much. But it is not a good winter mulch. And I hate picking dirt and dead leaves from it.

For a volcanic look, and for attracting heat during the day:

http://decorativeaggregates.com/gravels ... +10mm.html

What about wood chippings in bags and then packed firmly around the base of plants. No nitrogen issues. Wood stays dry hence potentially warmer. Bags of chippings may retain daytime heat from any sunshine and release at night. Not tried it yet but I am going to this Winter. soon!

fgtbell wrote:Sad to say - if we have extended cold like we did in December, with daytime temps only hitting -4C, no amount of mulch will retain the heat - it will leak out anyway.

That was a 1 in 100 year event though so chances of that happening again this year are very low. Plus we are nearly half way through December already.

I suppose the mulch will all depend on the kind of plants you are growing really. different types of mulch for different plants with different requirements.

I would say bark mulch as it allows for pockets of air which will insult and will in time break down improving the soil. But as has already been said, prolonged cold will cause the ground to freeze solid anyway.

We had a topic similar to this before but was about decorative surfaces. It seemed all had their +s and -s. Another thing to watch is... I infected a Dicksonia antarctica with fungi from a bark mulch and haven't managed to get rid of the fungi yet.

fgtbell wrote:Sad to say - if we have extended cold like we did in December, with daytime temps only hitting -4C, no amount of mulch will retain the heat - it will leak out anyway.

No sure I agree with that, a mulch of 33cm of snow last December allowed the 10cm soil depth temp to rise from +2C to +5C while temps were around -1 to -10C above the snow. Don't forget that you are trying to stop the ground losing heat at the surface, but there is an immense amount of low level heat 3 feet down. This remains about 10C all winter. Stop all heat escaping and the surface will rise to near 10C also. However, completely insulating the ground will allow the air above to cool more, as happens above a snowfield, so it is a balance.

This is a bit controversial, but when I was a landscaper the best mulch we ever used was well rotted horse manure… I’m talking the black stuff that doesn’t smell!
It supresses weeds, feeds the plants/soil and with three or four inches laid on top of the soil it will help to keep the cold out and retain some heat in the ground in summer.

Tony

Apparently loads of seaweed is superb...if you live near the coast.