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Prune Your Roses

And cut out all stems infested by cane borers

Roses need to be pruned yearly to keep the plants strong and healthy. Now is the time to prune summer-flowering roses. Wait to prune spring-flowering roses until after they have flowered.
    Hybrid T and floribunda roses in the ground five years or less should be pruned to within 12 inches of the graft union.

Cultivate Your Asparagus Bed

Now is the time to hoe out the weeds and cultivate the soil over the dormant roots of asparagus in your bed. Both chickweed and henbit have had excellent growing conditions this winter and are probably covering the soil. It is simpler to remove them now than after the asparagus spears appear. Avoid deep cultivation of the soil so as not to damage the asparagus crowns.

    As Hybrid Ts and floribunda roses grow older, do not prune so severely. The stems of older roses are generally pruned to within 18 to 24 inches of the graft union. However, all side branches, or suckers, less than a pencil-width in diameter should be removed, and all remaining branches pruned, leaving at least two buds on each branch.
    Mounding roses and old-fashioned roses are grown on their own roots and thus can be pruned to the ground without loss of variety. Mounding roses are becoming very popular because they are generally disease- and insect-free and flower all summer long. I even prune mine with the lawn mower.
    When you’re pruning roses, be on the lookout for cane borers. I recently visited a garden where almost every rosebush was infested with cane borers, yet the owner was not aware of the problem, even though she complained that many of her rose bushes were dying out.
    Cane borers are especially damaging to grafted roses such as hybrid Ts and floribunda. Once the cane borers penetrate to the graft union — which is that knob that separates the stems from the roots — the top of the plant dies. As the root system is of a different species, sprouting occurs from the roots. Typically, flowers from the root sprouts are not as desirable.
    Cane borers are also a problem on Knock-Out roses, but because these roses are propagated from cuttings, the sprouts that emerge from the roots are the same. However, cane borers kill branches in Knock-Out roses.
    Evidence of cane borers in roses can be detected by examining the cut ends of each stem. Look for a small perfectly round hole the size of the lead of a pencil. When you see such hole, keep pruning that stem until you see nothing but solid stem wood. The prunings of infected stems should either be burnt or placed in the garbage. Do not put them in the compost pile.
    To prevent future cane borers from infecting your roses, place a drop of nail-polish or carpenters glue on the cut end of each stem that is pencil size or larger in diameter. Cane borers generally do not infest stems smaller than a pencil in diameter because those stems have not yet developed a pith. Even a thumbtack stuck into the cut end of the stem will prevent cane borers.

Ask Dr. Gouin your questions at [email protected]. All questions will appear in Bay Weekly. Please include your name and address.