Frequently Asked Questions

Question:
I saved last year's poinsettia. How do I get it to flower for Christmas?
Answer:

Poinsettias are short-day plants.  Short-day plants grow vegetatively during the long days of summer and produce flowers when days become shorter in fall.  In order for poinsettias to flower for Christmas, they must receive complete...

Question:
When mowing the lawn, what is the proper mowing height?
Answer:

Kentucky bluegrass lawns should be mowed at a height of 2½ to 3 inches in the spring and fall months.  Mow bluegrass lawns at a height of 3 to 3½ inches in June, July, and August.  A higher mowing height in summer helps to cool the...

Question:
What should I do to my summer-bearing red raspberries now that they are done producing fruit?
Answer:

After the last harvest, prune off the old fruiting canes at the soil surface.  Remove the pruned material from the garden and destroy it.   

Question:
What is the proper way to plant a container-grown tree?
Answer:

When planting a container-grown tree, dig a hole that is 2 to 3 times wider than the diameter of the container.  The depth of the hole should be 2 or 3 inches less than the height of the soil ball.  Slope the sides of the hole so the...

Question:
Large areas of my lawn have turned orange. Why?
Answer:

The orange color is likely due to rust.  Rust is a fungal disease.  It can be diagnosed by walking across the lawn in white shoes.  As you walk across the lawn, bright orange spores of the rust fungus will rub off onto the shoes,...

Question:
How can you tell when to harvest honeydew melons?
Answer:

Unlike muskmelons, the fruit of honeydews do not slip off the vine when mature.  The best indicator of ripeness is a slight softening of the blossom end of the fruit.  There may also be a subtle change in the color of the honeydew....

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:
What are the symptoms of downy mildew on impatiens?
Answer:

Symptoms of impatiens downy mildew initially appear as yellowing of infected leaves. The yellow-green foliage may initially be confused with a nutritional deficiency. As the infection progresses, leaves may curl downward and a white, fuzzy growth...

Question:
When can radishes be planted in Iowa?
Answer:

Radishes can be planted as soon as the ground can worked properly in spring.  This is often late March in southern Iowa and mid-April in northern counties.  Successive plantings can be made every 7 to 10 days through May.  Radish...

Question:
This fall some of the needles on my white pines have turned yellow and begun dropping to the ground. Is this a problem?
Answer:

The loss of needles is probably due to seasonal needle drop. Deciduous trees, such as maple and ash, drop all of their leaves in fall. Though it largely goes unnoticed, evergreens also lose a portion of their foliage (needles) on a yearly basis....

Question:
What is the proper way to divide peonies?
Answer:

September is the best time to divide peonies.  By September, peony plants have been able to store adequate food reserves in their roots.  Also, the replanted divisions have several weeks to get reestablished at their new sites before...

Question:
When should I harvest tomatillos?
Answer:

Gardeners should be able to begin harvesting tomatillos 75 to 100 days after transplanting.  For best flavor, harvest tomatillos when the husk changes from green to tan while the fruit is still green.  The size of the husk and fruit, as...

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:
There are horn-shaped, foul-smelling objects growing in my mulched flower beds. What are they?
Answer:

The foul-smelling objects are likely stinkhorns. Stinkhorns are a type of fungus or mushroom. The common name is derived from their appearance and smell. Stinkhorns usually appear in cool, wet periods in late summer and early fall.

Several...

Question:
When should I harvest my bell peppers?
Answer:

Bell peppers are usually harvested when large, firm, and dark green (immature stage).  They may also be allowed to fully ripen to red, yellow, orange, or other colors.  Fully mature bell peppers are slightly sweeter and contain higher...

Question:
What are jostaberries?
Answer:

Jostaberries are a cross between black currants and gooseberries.  Plants are vigorous and may grow to a height of 6 to 8 feet.  Jostaberry fruit are similar in size to gooseberries and black in color.  Plants possess excellent...

Question:
I recently received a flowering mum from a florist. Can I plant it outdoors?
Answer:

Florist or greenhouse mums are sold throughout the year at floral shops, supermarkets, and other retailers.  Unfortunately, florist mums do not perform well when planted outdoors.  Most florist mums will not survive the winter when...

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

Mowing frequency is based on the growth rate of the turfgrass and mowing height. As a general rule, never remove more than one-third of the total leaf surface at any one mowing. Shorter mowing heights require more frequent mowing. A lawn...

Question:
I have some small, purplish spots on the canes of my black raspberries. What is it and how can it be controlled?
Answer:

The small, purplish spots are most likely due to anthracnose.  Anthracnose is a serious fungal disease of raspberries, especially black raspberries.  The disease is readily recognized by the small, purplish spots that develop on young...

Question:
What is the proper way to plant a bare-root tree?
Answer:

Prior to planting, soak the tree’s roots in a bucket of water for 1 to 2 hours.  Also, prune off damaged or broken roots. 

When ready to plant, dig a hole that is 2 to 3 times wider than the spread of the tree’s root system....

Question:
When is the best time to sow grass seed?
Answer:

Late summer (mid-August to mid-September) is the best time to establish a lawn from seed in Iowa.  Late summer seeding has several advantages over spring seeding.  The seeds of cool-season grasses germinate quickly in the warm soil of...

Question:
How do I know when a watermelon is ready to harvest?
Answer:

Harvest when the underside or "belly" of the melon turns from a greenish white to buttery yellow or cream. This color change is especially pronounced on the dark green-skinned varieties. It is often less noticeable on lighter-skinned watermelons...

Question:
The leaves on my maple tree are covered with a black, sooty material. What is it and is it harming the tree?
Answer:

The black sooty material is likely sooty mold.  Sooty mold is caused by several different fungi.  The fungi don’t infect plants, but grow on the sugary honeydew excreted by aphids, scales, mealybugs, and other insects.   In...

Question:
Is it possible to control downy mildew on impatiens?
Answer:

In landscape plantings, control of downy mildew on impatiens with fungicides is not practical. Sanitation is the best management strategy for this disease. Remove and destroy infected plants as soon as they are noticed to reduce the spread to...

Question:
When should radishes be harvested?
Answer:

Radishes can be harvested 3 to 5 weeks after planting.  Periodically check their development by pulling one or two plants as they approach maturity.  Harvest radishes when roots reach useable size (about 1 inch in diameter). ...

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