Ask the gardening expert

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Last week you talked about house plants that don't keep their bloom all winter, such as poinsettia and cyclamen. But aren't there any that would keep blooming all winter?

If you are thinking of blooming plants, they may be few and far between. Most have a bloom cycle, then set seed and are vegetative until they set their next bloom. There are also plants that bloom in the darker days of winter, such as some hoyas and some others. But I'm going to talk a little about some exceptions.

There are winter blooming plants such as zygo cactus and others, but I would rather mention the summer bloomers I've had bloom all year for me — with absolutely no effort on my part — other than some water when the soil's dry. These plants bloomed not only in my small hobby greenhouse, but in a west-facing window in the house. And, of course, there is the stand by: zonal geraniums. They bloom like mad all winter long in my greenhouse.

But the star of the show in my estimation is the 'Dragon Wing Begonia.' I have eight plants in 8-inch pots that are beginning their fourth year in my laundry room window and greenhouse. They have never gone out of bloom. They are amazing. I cut down a few at a time, give a little bloom fertilizer and before long, they are back in bloom.

So here is my suggestion: Early next summer find some Dragon Wing begonias at any garden center; they come in many colors. Enjoy them outdoors in summer. Then, next fall, inspect them for insects or disease and bring a number of them in, if you have room. Bring several and be prepared in the rare case of plant failure. Repot them into nice roomy pots. Cut some back and leave some blooming; rotate the bloomers. Feed each pot a half dose of bloom fertilizer once in a while. The soil can become dry on top between waterings; don't let them stand in water. No indoor plant likes standing in water.

My mom gave me some pots 6 inches and larger that had annuals, and other things in them. She told me that some plants suffered some powdery mildew toward the end of summer. I want to use the pots again, but wonder about the dirt. Am I apt to the same disease if I use the pots and dirt this spring?

I wouldn't want you use the soil again since you knew there was a disease. I wonder what other pathogens might be in the soil and pots; the powdery mildew is only the one she identified.

It's a good idea to protect your investments: start clean. Add the used soil to compost, along with some nice organic material, and let it 'cook' for a while before reusing it later on.

As for the pots, give them a good scrubbing with a brush and a sudsy detergent solution. Finish by rinsing each in a 10 percent chlorine rinse(10 cups of water to 1 cup of chlorine bleach).

Let them air dry, and they will be ready to begin a new growing season.

I am repeating this from last year as I was asked this question again by someone in the grocery store, just this week.

I'm worried that I may have waited too late to mulch some of my perennials. The cold days have gotten to them. Is it too late to mulch them now, or is the damage already done?

I'd be guessing as I don't know which perennials you are concerned about, (she didn't know the names of the plants) but I would say that most herbaceous plants are just fine. They are the ones that the tops die down in wintertime; it's their way of protecting themselves from extreme cold. I don't expect that many of these perennials are being hurt in the temperatures we have had so far.

Now is a fine time to add mulch around shrubs, trees and perennials. It's not bad that you waited to add mulch, since the soil is now nice and cold before you add the protective mulch. The cold and the mulch will help plant roots remain protected until the spring's warmth wakens them.

In late winter don't let yourself be fooled into removing the protective mulch too early, should we experience some spring-like weather in February or early March. In winter the reason we mulch is to keep the roots safely cold until winter is over and the soil is warming.

A couple more thoughts on winter mulch: make sure it is not touching the trunks of the plants.

Also slugs like hiding in mulch, so be diligent. I found a few slugs under pots just this week. I also noticed and destroyed some slug eggs; they look like tiny perils.


Celeste Lindsay is a WSU-certified master gardener. Send questions to mslindsay8@gmail.com.