Frequently Asked Questions

Question:
Several new shoots on my crabapple have turned brown and wilted. What is the problem?
Answer:

Fire blight is probably responsible for the wilted shoots on your crabapple.  Fire blight is caused by  the bacterium Erwinia amylovora.  Plants susceptible to fire blight include apple, crabapple, pear, hawthorn, and...

Question:
What are the benefits of aerating the lawn?
Answer:

Aeration relieves soil compaction, improves water and nutrient movement in the soil, and prevents thatch accumulation.  Aeration improves the growing conditions for the turfgrass plants and results in a healthier, more vigorous lawn. ...

Question:
How do I control weeds in my asparagus planting?
Answer:

Weeds compete with asparagus for light, water, and nutrients and will reduce asparagus yield and quality if not controlled. Cultivation and hand pulling are the best ways to control weeds in an asparagus planting.  Hoe or...

Question:
Can hollies be successfully grown in Iowa?
Answer:

American holly (Ilex opaca) and English holly (Ilex aquifolium) are prized for their glossy, green leaves and brightly colored fruit. Sprigs of both hollies are often used in wreaths, centerpieces, and other Christmas...

Question:
How often should I fertilize hybrid tea roses?
Answer:

To encourage vigorous growth and abundant bloom, hybrid tea, floribunda, and grandiflora roses should be fertilized two or three times a year.  Fertilizer applications can be made in early spring (immediately after pruning), during the first...

Question:
What are the proper pruning procedures for purple raspberries?
Answer:

Proper pruning of purple raspberries promotes high yields, helps control diseases, and facilitates harvesting and other maintenance chores. 

In March or early April, remove all small, weak canes, leaving only 4 or 5 of the largest,...

Question:
How often should I pinch my mums?
Answer:

Pinch chrysanthemums 2 to 3 times from spring to mid-summer.  Remove the stem tips when the shoots are 6 to 8 inches tall.  New lateral shoots will develop along the stems.  Pinch again when these new shoots reach a length of 6 to...

Question:
I planted some lima beans this spring, but the plants produced only a few pods. Why?
Answer:

In the midwest, yield is largely determined by weather conditions.  Lima beans grow best when temperatures are between 70 and 80 degrees Fahrenheit.  They also require 1 inch of water per week (either from rain or irrigation) during...

Question:
What are some good low-growing groundcovers?
Answer:

Plant heights vary somewhat based on the growing conditions at the site.  However, there are several groundcovers that are 12 inches or less in height. 

Shade Groundcovers

Low-growing groundcovers for shade include:...

Question:
When should I harvest beets?
Answer:

Beets may be harvested when the roots are 1 inch in diameter.  However, the main crop usually isn’t harvested until the roots are 1½ to 3 inches in diameter.  (Beets larger than 3 inches in diameter are often tough and fibrous.) ...

Question:
I need to have some tree work done. How do I select a qualified arborist?
Answer:

Trees are valuable assets to the home landscape.  Occasionally the services of a professional arborist are needed to prune a large tree or assess the condition of a tree after a storm.  For many individuals, selecting an arborist is a...

Question:
What can I use as a mulch around my tomato plants?
Answer:

Several organic materials can be used as a mulch around tomato plants.  Suitable mulching materials include:

  • Dry grass clippings (Do not collect grass clippings from lawns that have been treated with a broadleaf herbicide...
Question:
My 'Sunburst' honey locust is not growing well. What could be the problem?
Answer:

The ‘Sunburst’ honeylocust has distinctive yellow-green foliage.  Unfortunately, it is not a vigorous tree.  It grows slowly and is susceptible to cankers and mimosa webworms.

Cankers, caused by fungal pathogens, are localized...

Question:
What is thatch?
Answer:

Thatch is the layer of dead and living plant material that forms between the soil surface and green vegetation.  It is composed of shoots, crowns, and roots.  Thatch, to some degree, is present in all lawns.  However, when thatch...

Question:
Is it a good practice to apply salt to an asparagus planting?
Answer:

In the past, some gardeners used salt to control weeds in their asparagus plantings.  However, salt is not effective in controlling many weeds, especially grasses.  Plus, continued use of salt over several years may result in high salt...

Question:
How often should I water my roses?
Answer:

Modern roses, such as hybrid teas, floribundas, and grandifloras, require watering during hot, dry weather.  The frequency depends upon weather conditions and soil type.  In most gardens, a thorough watering every 7 to 10 days during...

Question:
What are some good raspberry varieties for Iowa?
Answer:

Suggested raspberry varieties for Iowa include:

Summer-Bearing Red Raspberries for Iowa

  • ‘Boyne’
  • ‘Latham’
  • ‘Killarney’

Fall-Bearing Red Raspberries for Iowa

...
Question:
The leaves on several of my hostas have turned yellow, then brown, and finally collapsed onto the ground. What is happening to my hostas?
Answer:

The hostas may have petiole rot.  Petiole rot is a serious disease of hosta.  It is caused by the fungus Sclerotium rolfsii var. delphinii.  (Petiole rot can also affect daylily, peony, phlox, columbine, and other...

Question:
When should I harvest cauliflower?
Answer:

Cauliflower should be harvested when the heads are smooth, firm, and compact.  Full-sized heads may be 6 to 8 inches across.  Overmature heads will begin to open up and become “ricey.”  Cauliflower may be placed in perforated...

Question:
A yellow, foam-like growth has suddenly appeared in my mulched perennial bed. What is it and will it harm my plants?
Answer:

The growth in your perennial bed is probably a slime mold. Slime molds are types of fungi. Slime molds feed on bacteria and other organisms in the mulch. They do not harm plants.

Slime molds are usually a temporary nuisance. Within a few...

Question:
When is the best time to plant rutabagas in Iowa?
Answer:

The rutabaga performs best when planted in summer for a fall crop.  Sow seed at a depth of 1/4 to ½ inch from June 15 to July 15 in Iowa.  Rows should be spaced 18 to 24 inches apart.  Thin the planting within a few weeks of...

Question:
When would be the best time to prune potentillas?
Answer:

Summer-flowering shrubs, such as potentilla and Japanese spirea, bloom in summer on the current year’s growth.  Prune summer-flowering shrubs in late winter or early spring (March or early April in Iowa).

Question:
Is a tomato a fruit or a vegetable?
Answer:

There are different ways to classify or categorize plants and plant structures.  Botanically, the typical plant has roots, stems, leaves, flowers, and fruit.  The root is the edible portion of carrots, radishes, beets, and parsnips....

Question:
How do I get rid of moles in my yard?
Answer:

Trapping is the best way to get rid of moles.  Trapping isn't easy, but it does work.  Patience and persistence are required.  Traps can usually be found in hardware stores and garden centers.  When using traps, carefully...

Question:
Do I need to remove my grass clippings to prevent thatch development?
Answer:

Grass clippings contribute very little to thatch development because clippings are primarily cellulose and decompose quickly.  There is no need to remove grass clippings when lawns are mowed properly.  Infrequent mowing of tall grass...

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