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I'm using mulch on my trees and shrubs here in upper SC. We have heavy clay soils. I've been putting mulch around all the trees and shrubs I plant, but I feel like some of them don't need it anymore or at least there is a point when the benefit doesn't out weigh any expense or effort.

For instance, we planted a maple tree in the yard. There aren't any flowers or berries that need the extra moisture retention and I'm sure after the 3-4 years it's been since I planted it, the roots have grown deeper and wider than the one bag of mulch I put on it can cover. I feel like I'm wasting my time and effort. Like it's only there to prevent someone from hitting the trunk with the mower. The same thing goes with my crepe myrtles. I feel like they're starting to get big enough that my bag of fertilizer isn't doing what it once was.

Other of my plants, I'll probably continue mulching because I feel it helps with flowering or fruiting. For instance, my azaleas, small magnolias, flowering cherry, figs, blueberries, etc... However, I just planted some pecan trees and I feel like once they get big enough, it's no longer helping enough to justify buying it and putting it out.

Occasionally, they have a good deal around here with Homedepot putting it on sale at 5 bags for $10, so it's not that expensive, but at current count, I'm taking care of 28 trees, shrubs, etc... It'll add up. Not to mention me having to lug them around and put them out.

So what do you guys think? Is there a certain point where it's no longer helpful to mulch? Like if they get over a certain size or if they've been planted a couple of years and you're not trying to get fruit off of them. Thanks for the help. I'm in Zone 8A.

  • Can I ask what exactly you're using as a mulch? – Bamboo Mar 21 '16 at 18:16
  • Yeah, I'd prefer to be using compost, but it's more expensive and doesn't hold up as well. I'm currently using Vigoro Bark Mulch, just for water retention. It's not the best, but it's cheap and it works. Here is an example of their mulch: homedepot.com/p/Vigoro-2-cu-ft-Red-Mulch-480978/205606416 – Dalton Mar 21 '16 at 18:20
  • Just incase something ever happens to that link and someone is reading this for their own benefit in the future. The site lists it as 100% premium shredded wood mulch from ponderosa pines. It says it's mulch and soil council certified. It is also dyed red, however I believe the brown and black versions are dyed as well. I don't know what they use to dye it or whether it's healthy or not. It's never hurt my plants. – Dalton Mar 21 '16 at 18:23
  • You might check whether your tree(s) roots are in the mulch or in the 'heavy clay' beneath. Also check whether the roots have extended beyond the mulched area or not. – Jim Young Mar 22 '16 at 3:59
  • I know their not in the mulch, because due to whatever reason (probably the person mowing not paying attention and it breaking down over time) the mulch is mostly gone in a year. I scrape it back to fertilize, then put back what's left and add new mulch. I don't know how to check if the roots are outside the mulch radius without digging them up, which seems counter productive. – Dalton Mar 22 '16 at 12:10
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It depends on the tree and its natural habitat. If the tree is normally found growing in a forest with its roots shaded by other trees, and its roots covered by forest litter, then that's what you should be aiming to do. Mulching helps protect the roots from heating up in strong sun light, fertilises the roots, and maintains a moisture layer around the roots.

For example deciduous trees drop their leaves in fall to seal their branches from winter, to suppress the growth of competitors around their bases, and to recycle the nutrient from the leaves to their roots.

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In principle, t's always helpful to mulch, provided the mulch is organic in origin - the mulch breaks down and improves the soil beneath. As to whether you really need to use it, that's another matter - if it gets extremely hot and very dry during summer, that mulch will conserve moisture and may act as a barrier to hot sun. As far as I'm aware, where you live does have high summer temperatures, but also high humidity, and the average precipitation is relatively high, but that's an average. If you regularly get three months of dry and hot weather, then the mulch is serving a useful purpose. If you get regular rainfall despite the heat, then you might choose not to use it around plants which have been in situ longer than 3/4 years.

  • Yeah, we definitely don't get dry weather. It's humid all the time. Occasionally, it won't rain for a period of time, but that's usually rare. I didn't realize the humidity made such an effect till we took a cruise to Mexico. It was over 100% but the humidity was low and it felt like it was in the 80's. – Dalton Mar 24 '16 at 17:01
  • High humidity is why we're always cold in the UK in winter, even though the air temps might be well above freezing. My Latvian friend says she's colder here than at home, where it gets -35 deg C every year... – Bamboo Mar 24 '16 at 21:08

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