Frequently Asked Questions

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:
Should I treat my ash trees to protect them from emerald ash borers?
Answer:

Insecticide treatments are available to protect ash trees from the emerald ash borer.   However, treatments should be undertaken only when necessary to prevent excessive and needless use of insecticides. 

Insecticide treatments...

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

Most lawns in Iowa require 1 to 1½ inches of water per week.  When watering the lawn, apply this amount in a single application or possibly 2 applications 3 or 4 days apart.  Avoid frequent, light applications of water which promote...

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:
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 do I control water grass in my lawn?
Answer:

“Water grass” is an ambiguous name.  Several plants are occasionally referred to as water grass.  Two common lawn weeds that are sometimes referred to as “water grass” are crabgrass and yellow nutsedge. 

Crabgrass

...

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:
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:
There is a large growth on the trunk of my maple tree. What is it?
Answer:

The growth on the trunk of the maple tree is likely a burl.  Burls are abnormal swellings or growths that develop on the trunks and branches of trees.  Burls can be found on deciduous trees and evergreens.  The exact cause is...

Question:
There are golf ball-sized growths with horn-like projections on the branches of my pin oak. What are they?
Answer:

The growths on the pin oak are a type of gall.  Galls are abnormal growths of plant tissue induced to form by mites, insects, or other small organisms.  The galls on the pin oak are called horned oak galls because of the horn-like...

Question:
I planted several pine trees this spring. How long should I continue to water the trees?
Answer:

The roots of trees continue to grow until the ground freezes.  If the weather is dry, continue to water the newly planted trees until the soil freezes in winter.  
 

Question:
There are small, black beetles feeding on my raspberries. What can I do?
Answer:

The small, black beetles are likely sap beetles.  They are also known as picnic beetles or picnic bugs.  Sap beetles commonly feed on over-ripe or damaged fruits and vegetables in the garden.  

Sanitation is the best...

Question:
How do I stop yellowjackets from feeding on my raspberries?
Answer:

Yellowjackets are social wasps that build paper nests in the ground, a log, building wall, attic, or other sites.  The workers from the colony travel up to a few hundred yards from the nest while looking for food.  In early summer, the...

Question:
There are small, white worms in my raspberries. What are they and how can they be controlled?
Answer:

The small, white worms are likely the larvae of the spotted wing drosophila.  Spotted wing drosophila adults are small, yellowish brown flies.  Males have distinctive dark spots on their wings, hence the name spotted wing drosophila....

Question:
What is a good storage site for spring-flowering bulbs?
Answer:

Tulip, daffodil, hyacinth, and other spring-flowering bulbs usually begin arriving in garden centers and other retail businesses in late August.  Spring-flowering bulbs purchased in late summer should be stored in a cool, dry place (such as...

Question:
How do you store grapes?
Answer:

Sound grapes can be stored in perforated plastic bags in the refrigerator for up to two months. Optimum storage conditions are a temperature of 31 to 32 degrees Fahrenheit and a relative humidity of 85 percent. 

Question:
Is late summer/early fall a good time to plant trees?
Answer:

Mid-August through September is an excellent time to plant pine, spruce, and other evergreens.  (Evergreens planted in late October or November may not have adequate time to become established before the onset of winter and could be subject...

Question:
Which vegetables can be planted in late summer?
Answer:

Several vegetables can be planted in late summer for a fall crop.  For a fall crop, plant beets, carrots, Swiss chard, kohlrabi, and kale in early to mid-August, plant leaf lettuce and spinach in late August to early September, and plant...

Question:
There are white, raised spots on my potatoes. Why?
Answer:

The white, raised spots on your potatoes are probably swollen lenticels due to wet soil conditions.  Potato tubers are enlarged underground stems.  Lenticels are small openings in the tuber surface that allow for gas exchange. ...

Question:
My peonies appear to be covered with a white, powdery substance. What is it?
Answer:

The white, powdery material on the peony foliage is powdery mildew.  Powdery mildew is a fungal disease.  Powdery mildew occurs on a large number of plants (peonies, lilacs, viburnums, roses, garden phlox, bee balm, turfgrass, and many...

Question:
Why are some of my cucumbers misshapen?
Answer:

Poorly-shaped fruit are usually the result of poor pollination.  Poor pollination may be due to cool, wet weather and improperly applied insecticides that limit bee activity.  When insecticides are necessary, select an insecticide with...

Question:
Why are some of my cucumbers bitter?
Answer:

The bitterness in cucumbers is produced by the compound cucurbitacin.  Cucurbitacins are normally found in the leaves, stems, and roots of cucumber plants.  The cucurbitacins spread from the vegetative parts of the plant into the...

Question:
My hot peppers are setting fruit, but not my bell peppers. Why?
Answer:

In regards to fruit set, bell peppers are sensitive to high temperatures.  The optimum temperature range for flowering and fruit set on bell peppers is between 70 and 80 degrees Fahrenheit.  Hot peppers tolerate high temperatures much...

Question:
My tomato plants are flowering, but aren’t setting fruit. Why?
Answer:

Unfavorable weather conditions are the primary reason for blossom drop on tomatoes.  High daytime temperatures (above 85 degrees Fahrenheit) and low nighttime temperatures (below 55 degrees Fahrenheit) interfere with pollination, causing...

Question:
There are wart-like growths on the undersides of the leaves on my hackberry. What are they?
Answer:

The wart-like growths on the hackberry leaves are galls.  Galls are abnormal growths of plant tissue induced to form by mites, insects, or other small organisms.  They are quite common on trees.  

The gall found on the...

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