Frequently Asked Questions

Question:
Can sweet corn be planted near popcorn in the garden?
Answer:

Sweet corn should be isolated from popcorn and field corn to prevent cross-pollination.  The quality of the sweet corn will be lowered if it’s cross-pollinated by other types of corn.  For example, sweet corn pollinated by popcorn will...

Question:
There are big, hairy worms and tent-like structures in my walnut tree. What are they and how do I get rid of them?
Answer:

The “worms” are likely fall webworms.  Fall webworms are hairy, tan to yellow caterpillars.  As they feed, fall webworms construct tents or webs at the ends of branches.  Tents are initially small, but the caterpillars enlarge the...

Question:
When should I harvest herbs?
Answer:

Most herbs are ready to be harvested when flower buds appear on the plants, but before the buds open.  The leaves contain the maximum amount of volatile oils at this stage of growth, giving the greatest flavor and fragrance to the finished...

Question:
Some of the leaves in my river birch are turning yellow and dropping to the ground. Why?
Answer:

Hot, dry weather may be responsible for the leaf drop on the river birch. River birches shed some of their leaves in hot, dry weather.  Leaves in the interior of the river birch turn yellow and drop to the ground.  Healthy, well-...

Question:
How often should I mow my lawn?
Answer:

Kentucky bluegrass lawns should be mowed at the height of 2½ to 3 inches in spring and fall.  Set the mower blade to a height of 3 to 3½ inches during summer. 

As a general rule, never remove more than 1/3 of the total leaf...

Question:
I have several rows of grapevines. What would be a good cover crop between rows?
Answer:

Kentucky bluegrass is an excellent choice.  Bluegrass provides good cover, yet is less competitive than other cover crops.  Late summer (mid-August to mid-September) is the best time to establish bluegrass by seed.  Do not sow...

Question:
How do I care for garden geraniums?
Answer:

Garden geraniums (Pelargonium x hortorum) are attractive flowering plants for beds, borders, containers, hanging baskets, and window boxes.  Geraniums are easy to grow and provide color in the garden from May to frost....

Question:
My purple raspberry canes grow several feet tall and eventually flop over onto the ground. What can be done to prevent this?
Answer:

The shoot tips of purple and black raspberries should be pinched or cut off when the new growth reaches a height of 36 to 48 inches.  Remove the top 3 to 4 inches of the shoots.  Pinching encourages lateral shoot development and...

Question:
Are Louisiana irises hardy in Iowa?
Answer:

Louisiana iris is the collective name for several species of iris which are native to Louisiana and boggy coastal areas from Florida to Texas.  They are prized for their colorful white, blue, red, or yellow flowers.  Louisiana irises...

Question:
My cucumber plants are blooming heavily, but aren't producing many fruit. Why?
Answer:

Cucumbers and other vine crops are monoecious.  Monoecious plants have separate male and female flowers on the same plant.  Male and female flowers are similar in appearance.  However, the female flowers have small, immature fruits...

Question:
How do I care for a grapefruit tree?
Answer:

Grapefruit and several other types of citrus can be grown indoors in Iowa.  Indoors, place citrus plants in a sunny south or west window.  Water plants regularly when growing in spring and summer, less often in winter.  In spring...

Question:
The ears on my sweet corn are poorly filled. What are possible causes?
Answer:

Poorly filled ears are usually the result of poor pollination.  Hot, dry winds and dry soil conditions may adversely affect pollination and fertilization and result in poorly filled ears. Water sweet corn during pollination if the soil is...

Question:
My magnolia is infested with magnolia scale. What are my control options?
Answer:

Magnolia scale is the largest scale insect in Iowa.  Sap feeding by the scales causes stress to heavily infested plants and can result in stunted growth, yellowish foliage, branch dieback, or death of the plant.  Magnolia scales produce...

Question:
Can I place weeds and diseased plant debris from the vegetable garden in the compost pile?
Answer:

It would be best to place weeds that are producing seeds and diseased plant debris in biodegradable bags and have the material picked up and composed by a municipal or commercial composting facility.  The temperatures in home compost piles...

Question:
There are brown streaks in my apples. What is the cause and how can it be prevented?
Answer:

The brown streaks in the apples are probably due to the apple maggot.  The apple maggot is the most serious insect pest of apples in Iowa.  Apple maggot damage appears as knobby, misshapen fruit with small pits or blemishes on the fruit...

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:
There are blister-like growths on the undersides of ivy geranium leaves. What is the problem?
Answer:

Oedema is probably responsible for the lesions on the undersides of the ivy geranium leaves.  Oedema is not caused by an insect or disease pathogen.  It is a physiological problem.  Oedema is most often encountered in greenhouses...

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

The growth and fruiting characteristics of blackberries are similar to raspberries.  The blackberry plant’s roots and crown are perennial, while its stems or canes are biennial.  Blackberry canes are strictly vegetative during the first...

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...

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