Deadhead roses to bring them back to life

I have a long rose garden with plants that are not blooming. The roses are 5-10 years old, surrounded by rock mulch and the plants look great. What can I do to make them bloom again?

— Carol

Assuming that these are reblooming roses we’re taking about (there are some mostly older varieties that will only bloom once a year), the best way to get roses to re-bloom is to deadhead them when the first big flush of bloom is tapering off. Deadheading is simply removing the old spent flower and/or seed pod.

When you deadhead, it’s important to not wait until the plant has completely stopped blooming; the big majority of flowers should be over and done with but there will be full blooms and even flower buds that won’t open for a week or two. Waiting until every last flower is done will put off deadheading for a month or more and will delay or even prevent a good second blooming period.

You may have read that when deadheading, you should cut the stem back to a “five leaflet leaf.” The thinking was that a bud at the base of a leaf like that will be stronger and give faster regrowth and flowering. The problem is that research has shown that really isn’t the case; the bud at the base of a three leaflet leaf is just as strong as one lower down on the stem.

Since I’m not worrying about which leaf to cut back to and especially since I’m a lazy gardener, I just use my hedge shears to deadhead and my plants respond great. I just do a rough cutting back (6 to 12 inches) of the plant and just roughly “round” it off. The plant will push out new shoots in response to the pruning and should be blooming in three or four weeks. You can cut individual stems back if you want to be more careful, but it just takes longer.

I have lost about half of my blackberry patch the last three years. The CSU people said they didn’t know what was the problem, but would cut the affected plants out. The affected plants bloom as usual, but never set good fruit.

— Raymond

 

I’m afraid I can’t tell you what’s going on for sure, but there are three possibilities I can think of.

The first is an insect called the berry crown borer. This little critter bores down at the base of the cane and into the crown of the plant. The first symptom of borer is that the cane starts to wilt and die back. You can confirm this by cutting into the cane; you should see sawdust-like material in the center.

There’s a second borer called the berry cane borer that does much the same thing, but he starts up toward the tip of the cane and tunnels down through the center. If there’s wilting just at the tip, then it’s probably this guy.

Controlling them takes a bit of work and persistence. First, you want to remove any canes that are infested. If most of the canes are infested, I’d strongly consider replacing the plant with a new one. Insecticide drenches at the base of the plant right now in early September and again a month later should do the trick.

There are a couple of insecticides you can use, bifenthrin or permethrin. Mix either of these products according to the label directions.

The second possibility is spider mites. I didn’t see any direct evidence of them on the samples you sent, but they were a bit worse for wear by the time they made it here. However, the leaves look like they’re suffering from this little beast. The solution for spider mite is to give your plants a hard jet spray with plain cold water from the hose. Do this every day or two for a couple of weeks. It’s an old-fashioned, simple solution but it works amazingly well.

The last thought I have is that you have a fungal crown rot or root rot in your plants. These types of fungi usually need a high water environment in the soil or at the base of the plant to thrive. If the soil around these plants stays damp from your watering or runoff from another part of the yard, then you need to try to correct this.

Modifying the environment is really the best way to try to control diseases like this. I’m afraid I really don’t have any fungicides to recommend to you. The best way is to make the soil environment less favorable for the fungus and better for the berry. Don’t let any standing water accumulate at the base of the plant and allow the soil to dry a bit before watering deeply again.

Dennis Hill is the nursery manager at Bookcliff Gardens, bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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