Frequently Asked Questions

Question:
Are there any irises that can be grown in shade?
Answer:

Most iris species (bearded, Siberian, Japanese, etc.) perform best when grown in partial to full sun.  However, the crested iris (Iris cristata) prefers partial shade.  A native of the eastern United States, crested iris...

Question:
When should I harvest cucumbers?
Answer:

Harvest cucumbers every 2 to 3 days and promptly pick the fruits when they reach the desired size.  Pickling varieties should be harvested when the fruits are 2 to 4 inches long.  Slicing cucumbers should be 6 to 8 inches long and 1.5...

Question:
How long does it take a compost pile to break down?
Answer:

The rate of decomposition depends upon the composition of the compost pile, level of management, and other factors. A well-managed compost pile (one that is watered and turned regularly) containing a mixture of shredded plant material should be...

Question:
How can I keep raccoons out of my sweet corn?
Answer:

The most effective way to prevent damage to the sweet corn crop is to encircle the area with an electric fence.  A two-wire fence with one wire 4 to 6 inches above the ground and the other at 12 inches should keep the raccoons out of the...

Question:
There are small masses of a foam-like material in my red-twigged dogwoods. What are they?
Answer:

The foam-like masses in the dogwoods were probably created by the dogwood spittlebug.  The dogwood spittlebug is one of several species of this commonly recognized group of sap-feeding insects.  Spittlebugs are familiar because of the...

Question:
How do I control weeds in my garden?
Answer:

Herbicides can be used to supplement cultivation, hand pulling, and mulches. 

Hand Pulling

Cultivation, hand pulling, and mulches are the primary means to control weeds in the home garden. 

Cultivation and hand...

Question:
Several apples have formed on a newly planted fruit tree. Can the apples be allowed to mature or should they be removed?
Answer:

It’s generally best to remove all fruit that form on apple trees during their first 3 growing seasons.  Removal of the fruit maximizes plant growth and increases yields in later years.  Removing the fruit may also prevent limb breakage...

Question:
The leaves on my river birch are yellow-green. Why?
Answer:

In Iowa, the foliage of the river birch (Betula nigra) often turns a sickly yellow-green. The yellow-green foliage is due to a deficiency of iron. The problem is referred to as iron chlorosis. (A close examination of chlorotic leaves...

Question:
Should I remove the grass clippings when mowing the lawn?
Answer:

When the lawn is mowed properly, grass clippings do not need to be removed or bagged.  Small clippings filter down into the turf and quickly decompose, returning essential plant nutrients to the soil.  Lawn clippings do not...

Question:
I have wort-like growths on the undersides of my grape leaves. What is it and does it need to be controlled?
Answer:

The wort-like growths on the grape leaves were probably caused by the grape phylloxera.  The grape phylloxera is a small, aphid-like insect.  The grape phylloxera has a complex life cycle that affects the leaves and roots of the...

Question:
I planted a Martha Washington geranium outdoors in spring. Unfortunately, it didn't bloom all summer. Why?
Answer:

Martha Washington or regal geraniums (Pelargonium x domesticum) produce beautiful flowers.  Unfortunately, cool (50 to 60°F), night temperatures are required for flower formation.  Few flowers form during the summer...

Question:
My strawberry plants are growing in a strawberry pyramid. How do I protect the plants over winter?
Answer:

A strawberry pyramid is a type of raised bed.  In winter, temperatures in raised beds may be several degrees colder than ground level plantings.  Because of colder temperatures, strawberry plants growing in raised beds require more...

Question:
There are large, brown spots on my peony leaves. What should I do?
Answer:

Peony leaf blotch is probably responsible for the large, brown spots.  Peony leaf blotch is caused by the fungus Cladosporium paeoniae.  The disease is also known as red spot or measles.  Typical symptoms include glossy...

Question:
When can I harvest eggplant?
Answer:

Begin harvesting the large, oval varieties when the fruit are 2 inches in diameter.  Continue to harvest the fruit until they are 4 to 6 inches across.  At the proper harvest stage, the fruit will be firm and shiny.  Overmature...

Question:
Do I need to add an activator to my compost pile?
Answer:

It is not necessary to add an inoculant or activator to a compost pile. A compost pile should be composed of layers of plant material and soil or finished compost. The soil and finished compost contain the microbes that will decompose the plant...

Question:
When should I harvest sweet corn?
Answer:

Sweet corn should be harvested at the milk stage.  At this stage, the silks are brown and dry at the ear tip.  When punctured with a thumbnail, the soft kernels produce a milky juice.  Over-mature sweet corn is tough and doughy....

Question:
There is a pile of sawdust-like material at the base of a large tree. What could be the problem?
Answer:

It’s likely the pile of sawdust-like material was produced by carpenter ants.  Carpenter ants commonly nest inside older, hollow trees or in trees with dead limbs or branches.  Carpenter ants do not eat wood.  However, they...

Question:
When should I harvest garlic?
Answer:

Harvest garlic when the foliage begins to dry.  In Iowa, garlic is usually harvested in August or September.  Carefully dig the bulbs with a garden fork or shovel.  Dry the garlic in a warm, dry, well-ventilated location. ...

Question:
My apple trees have set a heavy crop of fruit. Do I need to thin the fruit?
Answer:

Apple and other fruit trees occasionally set too many fruit.

Thinning is necessary to:

  1. Obtain large, high quality fruit at harvest.
  2. Allow development of flower buds for next year’s crop, thus overcoming the tendency...
Question:
The inner growth in my arborvitae is turning brown. Is this a problem?
Answer:

The browning of the inner foliage is probably due to seasonal needle drop. It’s normal for evergreens (pine, spruce, fir, juniper, arborvitae, etc.) to shed their oldest (innermost) needles in fall. The innermost needles gradually turn yellow or...

Question:
How do I control dandelions and other broadleaf weeds in my lawn?
Answer:

In small areas, some weeds can be controlled by pulling and digging.  This method is best accomplished after a soaking rain or deep watering.  Unfortunately, pulling and digging is often ineffective on deep-rooted weeds. 

In...

Question:
The berries on my grapevines have shriveled up and turned bluish black. What happened to my grapes?
Answer:

Black rot is probably responsible for the damage to the grapes.  Black rot is caused by the fungus Guignardia bidwellii.  This fungal disease is common in home and commercial vineyards in Iowa, especially in warm, humid summers...

Question:
How can I keep birds from eating my grapes?
Answer:

The best way to prevent birds from eating the grape crop is to place netting over the grapevines.  Netting can be purchased at garden centers or through mail-order companies.  When placing netting over the grapevines, make sure the...

Question:
Are marigolds pest free?
Answer:

While marigolds are seldom bothered by insects and diseases, they are not problem free.  Spider mites can devastate marigolds in hot, dry weather.  Grasshoppers can also cause considerable damage.  Aster yellows is an occasional...

Question:
How do I control weeds in my strawberry patch?
Answer:

Weed control is essential to insure optimal plant growth and fruit production.  Weeds compete with the strawberry plants for water, nutrients, and sunlight.  Weeds also reduce air circulation which results in fruit and foliage staying...

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