Garden Plot: How to prolong the life of roses

Rose bushes need a layer of mulch made of composted yard waste to thrive. Mulch from wood or bark can spread disease to plants. (Thinkstock)
How to prolong the life of your roses

wtopstaff | November 14, 2014 5:45 pm

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Save the date: Mike will appear March 15 – 17 at the Fredericksburg Home and Garden Show at the Fredericksburg Expo Center.

Mike McGrath,

WASHINGTON – Bones in Mount Vernon writes, “I have about 50 roses, all hybrid teas. I recently read your advice not to use wood mulch under them and to mulch with compost instead. Since I don’t have any of my own backyard compost, can I use Compro instead?”

Although I’m a big proponent of recycling, I do not advise anyone to use Compro for anything, under any circumstances. Although not revealed on its official website, Compro is sewage sludge from local waste water treatment plants. And all sludge contains toxins that were illegally sent into the sewer system by criminals and lazy home oil-changers.

But perhaps even more disturbing are the high levels of human medications that make it through the water treatment process — especially artificial hormones and antibiotic and antidepressant residues. For these and other reasons, the use of sludge is forbidden in certified organic agriculture.

Ah, but a different compost product from the same basic source, for example the State of Maryland, called LeafGro is fine. Leafgro is compost made from shredded fall leaves and other yard and garden waste, and makes a great mulch for roses.

Your choice of mulch can keep roses disease-free

In our last thrilling episode, I told Bones in Mount Vernon that he should not replace the wood mulch he is currently using under his roses with Compro.

But replace that wood mulch he should, as wood, bark and root mulches breed the diseases that roses are prone to, especially wood mulches that have been left in place from the previous season; they’re an incubator for disease spores.

If all you do is remove last year’s mulch from under your roses, you’ll greatly reduce disease problems. And if you replace that much with fresh yard waste compost, like LeafGro, you’ll prevent new disease spores from breeding.

Don’t feed your roses high explosives

Bones in Mount Vernon just emailed to say that he will be switching from his old wood mulch to a yard waste compost like LeafGro this spring. But he’s concerned about his roes getting enough to eat.

“Do you think that LeafGro alone provides enough fertility during the blooming season? I’ve been using Osmocote Controlled Release Fertilizer and Miracle-Gro LiquaFeed,” he writes.

Bones, once you stop using those highly concentrated chemical salts, whose other worldly use is to be packed into shells and fired at the enemy, you are going to love how your roses look this season.

Roses are not heavy feeders, no plant needs chemical fertilizers, and those artificial foods actually weaken the plants and make them much more attractive to pests like aphids and Japanese beetles and diseases like black spot.

Start the season with a fresh inch of compost under the plants and add a fresh inch in June or July. Your roses will be perfectly fed and uncommonly healthy.

Cane borers are a sure sign of overfed and wood-mulched roses

Now Bones emails with yet another issue: “The big problem I’ve had for the past few years is cane borers. I’ve been using enamel nail polish and Elmer’s wood glue to seal up their holes, but I still get borers wherever I prune or cut buds during the growing season,” he writes.

Sealing those holes won’t help, Bones. In fact, it could further weaken your plants. Let’s get your roses off drugs and bad mulches and I suspect the borers will disappear; happy, healthy roses are not their choice of prey.

So don’t use wood mulch anywhere near the roses, don’t feed them chemical fertilizers, don’t spray them with anything without asking me first, and don’t prune them after June except to deadhead old flowers or harvest new ones. Reserve pruning for the first few months of spring. Never prune in late summer or fall.

The five step path to award-winning roses

A few simple chores you perform early in the spring will practically insure that you have healthy, disease-free roses all season.

  1. Prune your roses about two weeks after they begin growing again in the spring to remove any dead, damaged or diseased canes and to open up the center of the plants to insure good internal airflow.
  2. Remove all those prunings and all the old mulch under your roses and throw it in the trash. Do not compost or reuse this infected red-bag material.
  3. Spread a yard waste compost like LeafGro an inch deep all around the base of each plant. Do not use wood, bark or root mulches under roses. And do not use Compro or other ‘composts’ that are actually sewage sludge.
  4. Harvest flowers freely early in the season. The more blooms you cut for indoor display, the more flowers the plants will pump out.
  5. Add a fresh inch of compost under your roses sometime in June or July. And then don’t prune for the rest of the season except to cut flowers or remove spent ones.

And that’s it — your path to disease-free roses.

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