Q: Last year powdery mildew spread across most of my garden including my pumpkin and squash patch. Do the spores overwinter in soil? Will turning soil help? Anything that should avoided at all costs? - Jeremy Haug, Grand Forks.
A: Powdery mildew is a fungal disease easily identified by its gray-white coating that begins as small, irregular circles on foliage eventually enlarging to cover entire leaves. Powdery mildew fungi attack many plant species including lilac, ninebark, peony, rose and garden vine crops like pumpkin, squash, cucumber and melons.
Powdery mildew spores overwinter in the soil, especially on plant debris. That's why fall sanitation is important, removing plant tops, vines, and fallen leaves of any plants affected. Fall tillage can help, by exposing spores to the winter elements. Powdery mildew spores can also be blown in on summer wind currents.
Prevention is the key to powdery mildew control, because once foliage is diseased, it will not revert to normal appearance and health. Prevention keeps foliage from becoming infected, or helps prevent the spread of disease spread, if detected early.
Powdery mildew is worse in hot humid weather, and when foliage remains moist. Practice prevention by avoiding overhead sprinkling. Water only the soil, keeping foliage as dry as possible. Water in morning, instead of evening, so surfaces dry quickly. Fungicides are readily available at garden centers for disease prevention in flowers, shrubs and vegetables. If plants have been troubled with powdery mildew in the past, fungicide applications can begin while foliage is still healthy, or at the earliest disease signs, especially when hot, humid weather begins.
Q: When is the best time to transplant lilacs: spring or fall? - Diane Widhalm, Fargo.
A: The most successful season to transplant lilacs, such as small sucker shoots, or any young lilac is early spring before they leaf out. The month of April works well, before new growth begins.
Q: I have houseplants that I'm transporting as we move to Pennsylvania from Missouri. The temperature during the day will be in the 50s, but I must make one stop overnight and the temperature is going to be in the upper 20s. Is there any way I can leave these plants in the car wrapped up somehow to prevent frostbite? - Lindsey Fowler, Jefferson City, Mo.
A: Night temperatures in the 20s will be difficult for houseplants, as these tropical natives can easily be nipped or killed below 40 degrees. The preferred protection method is to haul them into the motel along with your luggage, if possible.
If that's not workable, pack the plants in boxes, ice chest or plastic totes and layer newspapers, towels or blankets over and around the plants. Be sure the potting soil is well-moistened. Plants in dry soil suffer from cold temps more easily than plants whose soil is moist.
Then enclose the container in a large trash bag. Open the bag during the day to allow air movement. Plants can survive without much light for a few days. If you warm the car well before you retire for the night, and then warm it immediately upon waking, there's a chance the insulated containers will preserve enough warmth to keep the plants protected. Have a great trip.
If you have a gardening or lawn care question, email Don Kinzler at ForumGrowingTogether@hotmail.com. All questions will be answered, and those with broad appeal may be published, so please include your name, city and state for appropriate advice.