Solving your gardening dilemmas – Kansas City Star

Time to prune Knockouts?

Is now the time to prune Knockout roses, or should I wait for more buds? Also, please remind me of the formula for how far I should cut them back.

Yes, you may prune your Knockout roses now. We don’t have a formula for pruning Knockouts. You can reduce their height as much as you wish. Since they grow so quickly, you might have some dense, woody growth that you should thin on the inside. Crossing branches, branches that are shooting up vertically or directing their growth to the interior of the bush can be removed. And, of course, remove anything that is dead.

Knockout disease?

I heard that Knockout roses are getting some sort of infestation or disease that is killing them. True? If so, is there another type of rose that has the qualities of a Knockout?

I am unaware of an infestation. Perhaps you are referring to Rose rosette?

It is a virus that can affect any type of rose and attacks by way of a mite that floats in the wind. It does not spread from infected bushes to healthy bushes.

Once a rose is infected with Rose rosette, the bush must be removed with the roots and disposed of. Once the site has been free of the infected bush for a minimum of one month, you may plant another rose in the same hole.

Blooms fall off

Why do the first set of blooms fall off of my tomatoes and zucchini?

Squash have separate male and female flowers. The males always drop off after they shed their pollen. Female flowers may fall off because of a lack of pollination.

Blossom drop is often associated with cool temperatures as bees and other pollinators aren’t out collecting and transferring pollen as much.

Tomato blossoms drop off without setting fruit when night temperatures fall below 55 degrees, so that may be the problem with your first tomato blossoms.

Tomato blossoms will also not set and fall off when daytime temperatures exceed 90 degrees for extended periods.

Flower pots in gardens

I have slowly been trying to put plants in my flower pots and flower bed that come back every year. So far the only plant I have been able to plant in the flower bed and flower pots that comes back every year is sedum.

Could you please recommend plants that will return every year? My flower pots are on the east side of my house, and the flower bed is on the south side of my house.

Most perennials (plants that come back every year) can be planted in pots or directly in the ground. The pots should be large enough to protect the plants during the winter freeze and thaw cycles. Also be sure that there are adequate drainage holes in the bottom of the pot.

Perennials don’t bloom all summer, so you may want to add some annuals to your pots so you will have continuous color. Your east pots will use plants that only need partial sun, whereas the southern exposure areas use full sun plants.

Invasive honeysuckle

How can I help a friend determine if honeysuckle that has come over her fence from a neighbor’s yard is a marketed type of honeysuckle or the invasive bush form? I myself have been flamboozled by the invasive form. Hers hasn’t leafed out yet.

Invasive honeysuckles are one of the first plants to leaf out in the spring. That is one way to tell. For the most part all of the honeysuckles grown in the KC area can be invasive.

If your friend is local, she can bring a sample of the plant, after it leafs out, to the K-State Extension office in Olathe, and we will assist in identification. She can also email photos of the plant in question to


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