Mulch in raised beds.

Dade City, FL(Zone 9a)

I have 4x8 raised beds and can not find definitive information on whether or not to mulch on top of the beds. I'm thinking they need it though.

Irving, TX(Zone 8a)

I use pine needles to lunch my vegetable raised beds.
It really helps during our hot days in the summer.
I have been using it for years

Gainesville, FL(Zone 8b)

Quote from 2busygardening :
I have 4x8 raised beds and can not find definitive information on whether or not to mulch on top of the beds. I'm thinking they need it though.

For vegetable plants I would always use a mulch on a raised bed, especially if the soil does not have much moisture-holding capacity. I've actually found raised beds to be a really bad idea here in Gainesville, where the light sand soils mean that any applied water goes right through the bed and out the bottom, taking with it any applied fertilizers well below the root zones of your vegetables. The dry/wet cycling in these beds also means that most organic matter is oxidized VERY quickly - I've personally seen 2-inch diameter pieces of cypress wood (part of some stable bedding material) turn to dust in 3 months in a raised bed.

I would think that in order to use a raised bed system in Florida you would be forced to mulch, and even a heavy mulch might not be enough to maintain adequate soil moisture. IF the beds are very deep AND you are filling the beds almost entirely with organic media, then a mulch shouldn't hurt, and might help you keep enough moisture in the bed to keep your plants from going into shock in the intense heat and full sun that prevail down here most of the year. If you're in one of the areas where you get a nearly-constant breeze blowing through, a mulch would be a good idea even without the raised beds.

-Rich

Lisle, IL(Zone 5a)

I use bark mulch in all my beds, in-ground and raised. It allows me to water less frequently and keeps weeding to a minimum.

Charlotte, NC(Zone 7b)

2busygardening - I lived and gardened in Zone 9a (Palm Beach County) for over 30 years and found the only way to have decent "soil" was to have aged horse manure trucked in each August.

Wilmington, NC(Zone 8a)

I grow all my veggies in raised beds and don't use mulch. I bring in 14 yards of nursery blend that's made with composted poultry manure every 3 years and add Black Cow every season in between. There's no point having raised beds if they hold the same useless sandy soil from your yard.

Thumbnail by mccaine
Lisle, IL(Zone 5a)

My raised beds contain a mixture of store bought garden soil and homemade compost, but due to extreme heat and very low humidity I still find that it makes sense to mulch.

Everett, WA(Zone 8a)

Mulch helps the surface layer of soil resist pounding by rain or overhead watering.
And prteects the soil fromj overheating in summer sun, or rapid frost cycling in winter.

And if it is pine bark mulch, it will break down over a few years into a great, fibrous soil amendment that iomprovbes water retention..

Maybe if your RB soil drains too fast, you need a layer of plastic on the bottom to turn the whole thing into a huge self-watering "EarthBucket". As long as it doesn't flood, you could even run plastic up the RB walls to prevent evaporation through the walls.

Gainesville, FL(Zone 8b)

Quote from mccaine :
I grow all my veggies in raised beds and don't use mulch. I bring in 14 yards of nursery blend that's made with composted poultry manure every 3 years and add Black Cow every season in between. There's no point having raised beds if they hold the same useless sandy soil from your yard.

At the risk of seeming to contradict myself, I must respectfully disagree. When I was at school at the University of Georgia I had a series of gardens in heavy acidic red clay soils. I did my best to improve the soils, adding dolomitic lime and what organic materials I could scrounge, but I had little spare time and no spare money, so it was haphazard at best. I found that under those circumstances a raised bed kept the soil from becoming a quagmire during rainy spells and allowed me to get to the plants without compacting the soil, which was absolutely critical to prevent it turning to brick. Weeding was also simpler because I could mow or scythe the paths and focus on keeping the actual beds clean (as time allowed). I still miss the tomatoes I grew there, but never had any luck with root crops, and most perennial culinary herbs were a challenge to overwinter.

-Rich

Irving, TX(Zone 8a)

I have just finished to transplant out my summer plants.
I mulched with pine needles. This really work for me here. Definetely during the hot (100F ++) days of summer it made a huge difference.

Thumbnail by drthor
Wilmington, NC(Zone 8a)

Rich - I'm not sure that you are disagreeing with me but more making my point. I know all the benefits of raised beds but why would put poor soil (clay or sand) in raised beds? Why not fill them with compost and not worry about amending the soil?

SE Houston (Hobby), TX(Zone 9a)

Mccaine,
What size beds are those in your pic, and what is your usual yield per bed? ( I know your yield depends on what you're growing at the time, but just an average yield of the common veggies you grow would be helpful.)

Thanks!

Charlotte, NC(Zone 7b)

I use leaves that have been passed over with a mower several times as mulch. They are free and weedless! If I didn't have access to leaves, I would use pine needles.

The reason I mulch the leaves first is that I have found rain doesn't penetrate easily through whole leaves. With the help of earthworms, leaves break down into wonderful rich soil.

Gainesville, FL(Zone 8b)

Quote from mccaine :
Rich - I'm not sure that you are disagreeing with me but more making my point. I know all the benefits of raised beds but why would put poor soil (clay or sand) in raised beds? Why not fill them with compost and not worry about amending the soil?

Did you miss the part about me being a "starving graduate student" at the time? Don't know if you've been through the experience, but it is intense to say the least. I was on my way to school first thing in the morning, between classes and research I usually didn't get home until after dark (which was OK with me because I had no A/C, lived in a metal mobile home that was in full sun); I had no free weekends, and no disposable income. The closest thing I had to "compost" was the grass clippings I got when I mowed the little yard - maybe a couple of cubic feet a month at best, and I had no way to compost them (no "brown" to mix with the "green").

The raised beds - full of the clay I scooped out of the paths between the beds - nonetheless were far better for raising vegetables than leaving the ground flat.

-Rich



This message was edited Apr 4, 2012 5:39 PM

Everett, WA(Zone 8a)

I agree with Rich. Poorly draining soil in a raised bed is better for plants than poorly draining soil at and below grade. I assume that is mostly improved drainage and aeration.

And if you only have or can afford a LITTLE compost, it seems that putting walls around your small amount of half-decent soil lets you get more mileage out of what you do have.

I'm not sure why that is, but it's like having only one cubic foot of potting mix. It seems to "go farther" in several small pots, than spread on the ground.

I've noticed that many people who live in areas with large yards, many trees and much grass have toruble believing "I have few raw materials for composting". I live in an urban area with more parking lots than trees.

With copious free time, one might be able to harvest paper from businesses, and yard trimmings from 'lawn service' companies, but my garden chores always exceed my free time even before compost-hunting. it sems as if one can have either disposbale income, OR disposable time, but never both. And students and parents tend to have neither!

I asked one fruit-stand guy for his garbage, but it was already spoken for.

Wilmington, NC(Zone 8a)

Oh, I see. Yes I missed the starving graduate student part. And even though composting is free, Ricky's right, you need to have the time and resources to compost. I agree raised crappy soil is better than flat crappy soil. Getting back to the original post, I could mulch with pine straw because I have endless supplies of that in my back yard. But the cool season stuff doesn't need it. My peppers don't need it, and I'm growing my tomatoes in two seasons. So maybe I'll put some down in June.

Hutto, TX(Zone 8b)

When I used raised beds (before I was lucky enough to move to a 4-acre semi-rural lot) I always used mulch. It helped to control moisture and reduce the number of weeds. I used "composted" hay bales. I prepared the bales with heavy nitrogen fertilizer and a couple of weeks of daily soakings. That causes the bales to heat internally, killing a lot of the weed seeds and helping to breakdown the hay. There is an entire forum on growing IN the bales: http://davesgarden.com/community/forums/f/strawbale/all/ but I just used the recipe to prep the bales.

David

Brady, TX(Zone 8a)

David, I'm interested in doing what you did to the hay as I don't have access to any straw. Can you elaborate on how you did it? My small bale is "compressed" so I'm guessing I need to open it, maybe in a black bag? The highest nitrogen product I have is blood meal (12-0-0) -- will that work?
Thanks, Mary

Hutto, TX(Zone 8b)

Mary,

Leave the bale intact. The tight bale helps the reaction that heats the bale. Put the bale somewhere you have access to your water hose and where a soggy area of yard won't matter. Turn the bale on edge, where the ends of the grass is up and down. Soak the bale with water until it is completely saturated. Sprinkle about two cups of blood meal evenly over the top of the bale and water it in. Soak the bale every day, adding a cup or so of blood meal after soaking every other day.

The bale will start getting hot in a couple of days. In a week or 10 dayst the interior temp should reach 140-150 gdegrees. Keep soaking and adding nitrogen for another 2-3 days. That should heat up the bale enough to kill most of the grass and weed seed.

Brady, TX(Zone 8a)

Thanks David! Waiting for the sun to come up to get started ... oughta get out my camping headlight and go to work!!

Dade City, FL(Zone 9a)

Thanks for all the information. I did go ahead and mulch and WHAT A DIFFERENCE!!!

I use a 16 inch raised bed with a layered mixture of soil that I have to purchase. I add fresh each year as some of it does deteriorate to sand. It does pretty good, although now that I've mulched, it's going crazy.

My layers are:

top soil, black cow, peat, and miracle grow garden soil with some lime dusted in. It takes about two layers of each, with only the second to top layer of lime. Then, I do not mix it and water well. Wait 24 hours and plant. I don't remember where I got that from, somewhere on the internet, but it works well for me so far.

Fort Worth, TX(Zone 8a)

In the veggie bed, we use a combination of leaves (run over with the mulching mower) and straw. Mulch not only helps with water retention it helps the roots stay cooler, especially for those of us in the hot regions of the world.

Everett, WA(Zone 8a)

Mulch also keeps rain from pounding the top layer of the soil. Big rain drops can destroy the structure of the top 1/4" or so, turning it first to mud, and then (in my garden) to a hard, clay crust.

Mulch prevents that. And it keeps the Bok Choy cleaner, making it easier to wash.


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