Homegrown: Ash trees, Lantana and yellow daisies

When should I apply the Permethrin 38 to the ash trees to control borer?  What about the cherry and apricot trees?

— Judd

The time to spray for ash borer is about April 15–25. You want to thoroughly cover the bark of all the branches larger than 1 1/2 inches in diameter. That should protect the tree for a year.

The time to treat for peach tree borer on your fruit trees is late June through July. You CANNOT use the 38 percent Permethrin on fruit trees. You have to use a weaker strength product.

We recommend a drench around the base of the plant going up about 12 inches on the trunk. Apply the first one about June 20, repeat it on July 10 and again July 30.

If we use a cold frame, what is the lowest temperature that we could place ours over wintering geraniums, lantana, etc. out?

— Tom

Lantana will generally be more cold hardy than geraniums, and within lantana, some varieties will be hardier than others. In general, lantana will take short exposures to the upper teens.

Our problem here isn’t the temperature reading itself, it’s the duration and frequency of the cold.

This is a common question and misunderstanding from people who have moved here from warmer regions of the country.

I’ve talked to people from Albuquerque and Tucson who want to grow nonhardy plants here who say “well, it gets that cold back there so it should grow here.”

The truth is that we actually do get colder than these places, maybe by not that much, but the real difference is how often we get down to those temperatures and how long we stay there.

Albuquerque may get down to 10 or 15 degrees on an especially cold night, but its only a handful of times a year. It will drop down to that temperature for only a short period of time and quickly pop up to warmer temperatures.

Here, on the other hand, will typically see the low to mid-teens for a low for two or three months and each night we’ll spend several hours down at that temperature.

This makes a world of difference in whether a marginal plant survives or not. I would not let your cold frame go below 25 degrees for much more than a couple of hours. For the geranium, I’d try to keep it above 28 degrees.

I have been trying to find a plant select perennial called heliopsis “Tuscan Sun.” I need approximately 30 of them. Our landscaper planted Black-Eyed Susans but they only lasted that first year then came up all over by the seeds. I am not sure what happened unless he planted an annual. If you don’t carry this variety do you have any suggestions? I want yellow daisies about 20 inches tall.

— Kim

Tuscan Sun False Sunflower is a pretty good choice. It’s actually not a Plant Select selection but is a Proven Winners selection — one of those marketing things, but still a good group of plants.

Check around to see if you can find it, the common one is a variety called Summer Sun that might work for you.

You also might consider giving your original idea another try. It sounds like your landscaper planted the annual Rudbeckia (R. hirta) which sometimes comes back as a perennial but more often dies and reseeds itself.

Make sure you get the perennial one (Rudbeckia fulgida), the most common variety being Goldsturm. It should be pretty readily available. It has beautiful golden orange-yellow flowers that bloom for most of the summer and should be reliably hardy for you.

There’s a lot of confusion between the plants, especially when you start throwing in common names.

At our nursery, we call our perennial Gloriosa Daisy but some people connect that name to the annual type. We call the annual Black Eyed Susan but again others use that for the perennial type. Sorry for the confusion.

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

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