Most frequently asked gardening questions answered

By: 
Rob Zimmer
Columnist

Throughout the year in 2021, I received many questions from readers and listeners. Below are some of the most popular questions I received, multiple times, throughout the year. The fact that I received most of these questions multiple times indicates to me that these are things that are very important to gardeners in our area, and topics that touch their hearts. Enjoy my popular questions of the past year.

How do I get rid of powdery mildew on my plants?

Powdery mildew is an annoying and potentially destructive fungus that appears, often, in late summer. Normally, powdery mildew occurs when there is excessive moisture.

Depending upon the plant variety, one of the easiest ways to prevent powdery mildew is to buy new hybrids that are mildew resistant. Plants such as bee balm, tall phlox, ninebarks and other plants that are especially susceptible to this fungus have all been bred and hybridized into varieties that are mildew resistant. You will find this information right on the plant tag.

Like many garden diseases and pests, prevention is the key. If you wait to treat the disease until after you find it, it is likely already too late. It will be hard to control once you already have it. The key, then, is to prevent the disease from happening in the first place.

There are a number of good, all-natural fungicides and mildew preventives on the market. Follow the label directions and treat your plants from the time they first begin to appear, regularly, every two weeks or so, throughout the growing season to keep powdery mildew in check.

Watering from beneath, rather than from above, is another great preventive measure. Wet leaves are more prone to mildew.

When should I put up my hummingbird feeders? When should I take down my hummingbird feeders?

Depending on the weather, hummingbird feeders should be put out by the middle of April, definitely by May. Strong spring storms with south winds may bring hummingbirds earlier, and they will be looking for supplemental food sources. Typically, most hummingbirds return the second week in May.

Because of lingering migrants that may still appear in October and November, even into December, hunmingbird feeders should be left out as long as possible. It is a myth that feeders entice hummingbirds to stay longer. Hummingbirds are smart enough to know when it is time to leave. The reason many people leave out hummingbird feeders much longer is because there are several rare western species of hummingbirds that actually drift east late in fall and early winter. Many times, they show up at feeders in December, even in January.

What are the best plants to plant for Monarch butterflies?

The best plants to grow for Monarch butterflies include both nectar plants and host plants for caterpillars.

As most people are aware, milkweeds are the only plans that monarch butterflies will host upon as caterpillars. There are several great native milkweeds for our area including Common Milkweed, Orange Milkweed and Swamp Milkweed. Whorled Milkweed is great for sandy areas.

Nectar sources for monarchs include plants that bloom throughout the year. It is important to provide late season nectar sources for migrating monarchs into October. Wildflowers such as New England Aster, goldenrod, Joe pye weed, ironweed and other late bloomers are excellent choices. Purple coneflower, black-eyed Susan, meadow blazing star, bee balm, wild bergamot and coreopsis are also great for our area.

Excellent annuals for monarchs are lantana, zinnia, tall verbena and purple heliotrope.

I want to grow native wildflowers. What are the easiest ones to grow in our area?

The easiest native wildflowers to grow in our area are those that enjoy full sun and relatively dry conditions. Many of these can be grown in sand or clay, as native wildflowers are adapted to many areas once they are established.

Purple coneflower, Joe pye weed, ironweed, Orange milkweed, whorled milkweed, blazing stars of many varieties, black eyed Susan, brown eyed Susan, Rattlesnake Master, wild petunias, coreopsis, native grasses such as little bluestem, prairie dropseed, big bluestem and Indian grass, and many others, grow well in full sun and dry conditions.

For moist areas, cardinal flower, blue lobelia, Joe pye weed, swamp milkweed, bottle gentian, turtlehead, blue flag iris and others are excellent and easy to grow.

Why won’t my hydrangea bloom?

The most common problems for failure to bloom with hydrangeas are purchasing the wrong varieties for our area, as well as incorrect pruning. Incorrect location is another common problem.

Many gardeners tend to go for the big blooming, colorful varieties of hydrangeas in red, pink, blue and purple. Unfortunately, these hydrangeas, known as big leaf hydrangeas, require a little bit of extra care in our area in order to continue to bloom. If you purchase these varieties, expect to give them a little bit of tender loving care in order to keep them happy.

Generally, this means either completely protecting the plants in winter, or, placing in a container that can be stored inside an unheated garage, shed or basement for the winter.

This extra care is required because the big leaf hydrangeas bloom mostly on old wood, or wood that was formed the previous growing season. Because the blooms are already formed by autumn, they are easily frozen off in our cold winters. Therefore, it is necessary to protect the entire plant, even the leaf buds and new buds, not just the root ball.

Pruning is also unnecessary since the blossoms are already formed on the old branches. If you prune the plant back, you are cutting off next year’s buds.

This information only applies to the big leaf hydrangeas, as mentioned above.

For most other hydrangea varieties, those that are panicle or smooth hydrangeas, little care is required. However, it is important that the plant is placed in correct light. Old-fashioned hydrangeas, such as Annabelle, tend to prefer more shade, however, most of the newer varieties should be placed in full sun in order to bloom.

Panicle and smooth hydrangeas can be pruned back each year since they bloom on new wood that is formed each season.

The best way to learn how to completely care for your hydrangea is to check the plant tag for instructions or Google the name of your hydrangea for care in our area.

How do I prevent diseases on my tomatoes?

Much like the powdery mildew situation above, the key to preventing tomato diseases is to start early and continue preventive measures throughout the growing season. This means purchasing a good tomato disease preventer and applying regularly, normally every 10 to 14 days, throughout the season.

Many tomato diseases are caused by inconsistent watering. Inconsistent watering means the tomatoes get too dry or too wet for a period of time. While this cannot always be controlled, due to weather, we must do our best to provide consistent moisture. Plants that sit in water for too long or that go dry for too long are hard to get to come back completely and often weaken, showing signs of disease quickly.

This is one reason why it’s a good idea to grow tomatoes in containers, where moisture levels can be better controlled.

Another important aspect in controlling tomato diseases is to rotate your crops. Do not plant tomatoes in the same area of the garden each year. Even the tiniest pieces of diseased tomato plants left in the ground over winter, even the seeds, can spread disease throughout the year as they infect the soil around them.

What are the best plants to repel mosquitoes from my backyard?

Try planting containers filled with lavender, bee balm, scented geranium, lemon grass, lemon verbena, lemon thyme, sweet alyssum, Heliotrope and Swedish ivy. All of these plants are fragrant and tend to rebel mosquitoes from the area.

What are the best trees and shrubs to grow to attract birds?

In our area, berry producing shrubs are the best. This includes trees also. Mountain ash, crabapple, hackberry, Hawthorne, as well as conifers that produce seeds such as pines, spruces, tamaracks and junipers are all excellent.

For shrubs, ninebarks, highbush cranberry, viburnum varieties, serviceberry, witch hazel and others are great choices. Flowering shrubs such as ninebarks, lilac, spicebush and others are great for hummingbirds and insect eaters that are drawn to the blossoms.

Should I cut down my garden plants in fall or not?

My preference, especially for perennials and grasses, is to leave them standing throughout the winter season, for many reasons.

They provide shelter and food for birds and other wildlife, as well as safety and shelter for hibernating native insects and pollinators.

Annuals that provide seeds for birds, such as zinnias and sunflowers, cosmos and others should also be left standing as this is a great source of food for wintering birds.

Vegetable gardens are a different story. Because of the potential for diseases spread in the soil by even the tiniest pieces of plant debris, especially those in the nightshade family, vegetable gardens should be cleaned completely each season and all plant material removed from the soil. This gives the garden a fresh start every year in the spring.