Easy Way to Add Soil Organics with Rock Mulch Present

Q. I intend to remove the all rock layer around my roses and apply a 3 inch layer of quality compost, dig it in carefully, and cover it with western red cedar bark. However, the rock layer is convenient for blowing out all the leaves from other plants around my roses. How do I keep the rose area clean?

Roses growing in rock will start to be "unhappy" in about three to five years.

A. There is a way to make your roses happier and still leave the rock in place. I understand it was convenient before because your maintenance people would come and blow away all the debris with a power blower. With cedar bark, it will blow everywhere and make it difficult for your maintenance people to keep it clean.

Bark Mulch vs Woodchips

            First of all, bark mulch is not as effective as woodchips for a couple of reasons. Bark moves around in strong wind and when “blowers” are used in the landscape. Woodchips “lock” into place because of their rough edges and don’t move around even if the wind speed is 60 or 70 mph!  If wind is a problem I would not use bark mulch unless you are willing to “tidy up” afterwards.

Bark mulch is very attractive in landscapes but doesn't decompose quickly and blows with any type of wind.

            Secondly, bark mulch is pretty but it doesn’t improve the soil much. Woodchips disintegrate into the soil when moisture is present. In my experience, about half of it decomposes into the soil in about three years. This disintegration supplies organic matter back to the soil quickly. Woodchips don’t do that. They resist decomposition. That’s one important reason why bark comes from the outside of the tree and wood doesn’t.

Keep Your Rock Mulch

            Here’s how to keep your rock mulch and make your roses happier. Rake back the rock mulch 18 – 24 inches from your roses. Apply about ½ inch of good quality compost in this new area of bare soil and lightly incorporate it. Rake the rocks back and lightly water it in. Voilà! You have now added organic matter to the soil and made the roses happier.

High quality compost like Soil Pro has lots of benefits including better microorganism counts and loaded with plant nutrients.

            With very coarse rock mulch you can just sprinkle the compost on top of the rock and water it in. You will see improved growth from your roses in 3 to 6 months with either method. Repeat this about every two years.

 Benefits of Woodchips

What the roses benefit from is the decomposing woodchips and added organics to the soil. Rock (surface) mulch lets all the organics in the soil finish decomposing and your soil slowly becomes more mineralized. The organics in the soil start dwindling. As that happens, the roots of the roses finds itself in a progressively unhappy root environment. The unhappiness of the roots show up in the leaves with them yellowing, brown edges, and generally just not very productive.

Woodchip mulch is made from chipping the wood inside trees. Oftentimes the only way to get it is through "tree trimmers" like First Choice Tree Service.

 Don't Forget Iron

 If you still see some leaf yellowing, apply your favorite iron chelate to the soil around them once a year in late winter (late January or February in LV). If your favorite chelate doesn’t work then use the EDDHA iron chelate available from Viragrow ($20/lb) or Amazon or anyplace that sells it. 

EDDHA iron chelate is effective in whatever soil you have.

During mid to late summer or later you will have to spray it on the leaves. 
Viragrow is cheaper!

Iron chelates for leaf spraying is applied when most of the rose growth is finished for the season, like mid to late summer.