Douglas A. Spilker, Ph.D., is a consulting ornamental plant pathologist and entomologist, garden writer, and lecturer. Dr. Doug can be reached at

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Gardening Goofs
by Douglas A. Spilker, Ph.D.    

Do not add diseased garden plants, like these tomatoes, to the compost pile. Composting will not kill the pathogen, making it a source of disease next year.

One positive aspect of living in an area with four actual, distinct seasons is that each spring starts afresh – with enthusiasm and excitement for gardening, with an expectation of doing better than the year before. With a promise to learn from mistakes, we move optimistically into another growing season. Learning from others’ goofs may help you avoid these pitfalls:

Right plant – Right Place
Too many gardeners choose plants solely based on looks, not their required growing conditions. Ignoring this will likely result in failure. For example, it is a mistake to plant sun-loving plants in deep shade or in the spring under a leafless tree or planting shade-loving plants, such as Hosta, in an open area. They may look great at first, but then just dwindle away. Instead, study your landscape and note the various locations for light availability and duration, drainage, and soil conditions. Respect the specifics on the plant tags of new plant material or look up the information from websites.

Choosing the “right plant for the right place” is an important consideration for all types of landscaping. For example, never try to grow shade-loving Hosta in full sun, as leaf scald will undoubtedly result.

Select with your head, not your heart
Attempting to grow plant varieties that are a bad match for your climate is a losing battle. Do a bit of research before selecting your plants to increase your chance of success. Selection of plants that bring back sentimental memories is fun, but make sure they’ll be able to survive your climate.

Give ’em space!
Trees and shrubs that appear properly spaced when you plant them may still end up too crowd as they mature. That will result in competition for water, sun, and nutrients. Give trees plenty of room to grow; you can always fill in later.

Stagger shrubs and larger plants to provide more breathing room. The results may look odd initially, but after a few years, they will fill in. Proper spacing improves air circulation, which reduces the development of diseases such as powdery mildew, which thrives in high humidity.

Deadheading the spent flower heads of ‘Indian Summer’ brown-eyed Susan (Rudbeckia triloba ‘Indian Summer’) will encourage the setting of new flower buds.


Do you Deadhead?

Most gardening goofs are just doing something wrong; however, NOT doing something can also have undesirable consequences. The monotonous task of deadheading is too often neglected. Flowers need to be removed before they set seed in. order to prolong the blooming season. Deadheading is nothing more than removing dead or spent flowers, and actually encourages plants to set more flower buds. Most annual flowers, such as Petunia, Zinnia, and marigold (Tagetes spp.), as well as perennials like Rudbeckia and Echinacea, all flourish from deadheading. Learn which plants in your landscape benefit from deadheading, get to it, and see the amazing results!

Don’t toss just anything into the compost pile
A good trend is the increased use of backyard compost bins. By adding compost, you improve the overall texture of your soil enabling it to retain and drain water better. However, even though it is really easy to just toss pulled weeds and diseased leaves into the compost bin, fungal and bacterial pathogens can overwinter in dead plant material and seeds of weedy plants will not be killed during the composting process. Contaminated compost can easily reintroduce this year’s troubles into next year’s garden. Take the time to ensure you dispose of contaminated material properly, to reduce chances of infecting next year’s plants

Wait for the results
An avid gardener will tell you that proper soil health is the secret to success. Your soil’s pH level, mineral balance, density, and aeration are all factors in plant success. Most cooperative extension service offices provide soil testing services for a minimal charge. However, as the growing season approaches, the longer it will take to get your results and recommendations. If you do not submit your samples early enough, you might be tempted to start gardening before receiving the results. But wait, improving soil conditions after plants are in the ground is challenging at best.

Surprisingly, soils with extreme organic matter may have excessive potassium levels that can inhibit plants’ ability to absorb other nutrients. This rhubarb plant suffers from nitrogen deficiency. Get that soil tested to ensure the right balance.

Did I waste my money?
Although fall is the best time to establish cool-season lawns from seed, Midwestern winters commonly thin turf, making spring overseeding very tempting to bring back the turf density before summer hits. The spring application of a combination pre-emergent crabgrass preventer and fertilizer is a routine practice for most homeowners. However, you cannot do both tasks simultaneously – the crabgrass preventer will also kill emerging turfgrass seedlings! Do one or the other, or you will have wasted your money on the grass seed!

More is not better!
Using pesticides is sometimes a necessity after other pest control options have failed. Whether using natural or conventional pesticides, they should always be used according to the label instructions and precautions. Recommended application rates, application sites, and pests controlled have all been determined through extensive research and testing. There is a tendency to believe that if the labeled rate is good, then double that should be twice as effective. NOT TRUE. This is faulty logic. Higher rates may actually harm plants. Many liquid products contain petroleum-based ingredients to enhance the product’s performance, and higher rates of these products may cause leaf burn. Always read and follow the recommendations on the pesticide label for best results. (It’s the law.)

As gardeners, we’re constantly trying to reduce our gardening gaffes, but Mother Nature always seems to throw something new at us. But as they say, hope springs eternal … and there’s always next year!


A version of this article appeared in a September/October 2018 print edition of State-by-State Gardening.
Photography courtesy of Douglas A. Spilker, Ph.D.


Posted: 10/05/18   RSS | Print


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