Frequently Asked Questions

Question:
Japanese beetles are devouring my roses. What can I do?
Answer:

Japanese beetles eat the foliage, fruits, and flowers of over 300 plants.  When feeding on foliage, the beetles consume the tissue between the veins, leaving a lace-like skeleton.  Flowers and fruits are sometimes devoured completely....

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:
When and how do you divide bearded irises?
Answer:

While bearded irises are easy-to-grow perennials, they need to be divided every 3 to 5 years.  If not divided, plants become overcrowded and flower production decreases.  Crowded plants are also more prone to disease problems.  In...

Question:
When should I harvest cabbage?
Answer:

The harvest of cabbage may begin when the heads are firm and the size of a softball.  Mature cabbage should be harvested when the heads are solid and tight, before they crack or split.  Splitting is caused by excessive water uptake; the...

Question:
What would be a good planting site for the magic lily?
Answer:

The magic lily (Lycoris squamigera) is a rather intriguing plant.  Other common names include resurrection lily, surprise lily, hardy amaryllis, and naked lady.  The life cycle of Lycoris squamigera is different from...

Question:
Are there special corn varieties that are grown to produce "baby" corn?
Answer:

The small size of “baby” corn suggests that it’s a special variety.  However, most baby corn is actually grown from regular sweet and field corn varieties.  The ears are harvested when they are 2 to 4 inches long and 1/3 to ½ inch in...

Question:
The foliage at the ends of the branches on my honey locust are turning brown. Why?
Answer:

The browning of the honey locust foliage is probably due to the mimosa webworm.  Damage occurs when the caterpillars tie honey locust leaflets together and feed on the foliage inside the tightly compressed, protective webs.  Affected...

Question:
Is it possible to grow peanuts in Iowa?
Answer:

While peanuts are grown commericially in the southeastern United States, they can be grown in Iowa.  Their unique growth habit makes them a fun addition to the home garden. 

Growing Conditions

Peanuts grow best in loose...

Question:
My trumpet vine is growing vigorously, but isn't blooming. Why?
Answer:

The trumpet vine (Campsis radicans) is a woody vine that produces orange to reddish, trumpet-shaped flowers.  After planting, trumpet vines often don’t bloom for 3 to 5 years.  The trumpet vine has to grow and mature before it...

Question:
What is the proper mowing height for shady turfgrass areas?
Answer:

Do not mow shady areas less than 3 inches in height.  Because of the lower photosynthetic rates in shady areas, the turfgrass plants need a large leaf surface to manufacture adequate amounts of food.  The recommended mowing height for...

Question:
When should I harvest gooseberries?
Answer:

For jams, jellies, and pies, most gardeners pick gooseberries when they have reached full size, but are not fully ripe.  At this stage, the fruit are green, tart, and still quite hard.  Others prefer to allow the fruit to ripen to a...

Question:
There are yellow-green bugs eating the flowers on my roses. What are they and how can they be controlled?
Answer:

The yellow-green bugs are probably the adults of the northern corn rootworm.  The larvae of the northern corn rootworm feed on the roots of corn plants.  The adults (yellow-green beetles) appear in mid-summer and are present until frost...

Question:
When should I harvest raspberries?
Answer:

Raspberries are ripe when the fruit are fully colored.  Also, ripe berries slip easily from their receptacles, which remain on the plant.  If possible, harvest in the early morning hours before heat builds up in the fruit. ...

Question:
How deep should I plant bearded irises?
Answer:

When planting bearded irises, dig a hole large enough to accommodate the rhizome and roots.  Build a mound in the center of the hole.  Place the rhizome on top of the mound and spread the roots in the surrounding trench.  Then...

Question:
When should I harvest Brussels sprouts?
Answer:

Beginning at the base of the plant, harvest the buds (sprouts) when 1 to 1½ inches in diameter. Continue to harvest the sprouts higher up on the plant as they mature. Sprouts can be stored in a perforated plastic bag in the refrigerator...

Question:
Can I plant my Easter lily outdoors after it is done blooming?
Answer:

Individuals wishing to save their Easter lily (Lilium longiflorum) should place the plant in a sunny window after flowering.  Continue to water the plant when needed.  Fertilize once every 2 weeks with a dilute fertilizer...

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:
My bittersweet vine doesn't produce any fruit. Why?
Answer:

American bittersweet (Celastrus scandens) is dioecious.  Dioecious plants bear male and female flowers on separate plants.  Gardeners need to plant at least one male and one female bittersweet vine to produce fruit. ...

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:
When do I harvest currants?
Answer:

Currants typically ripen over a 2 to 3 week period.  Fully ripe currants possess the characteristic color of the variety (red, white, or black), are slightly soft and juicy.  For jellies and jams, harvest currants before the berries are...

Question:
There is a large, hard growth on the cane of one of my roses. What is it?
Answer:

The large, hard growth is probably crown gall.  Crown gall is caused by the bacterium Agrobacterium tumefaciens.  The bacterial disease can infect roses, grapes, apples, raspberries, willows, euonymus, and many other woody...

Question:
The bottom of my black raspberry leaves are covered with an orange substance. What is it?
Answer:

The orange substance on your black raspberry leaves is orange rust.  Orange rust occurs on black and purple raspberries and most varieties of blackberries.  Orange rust does not occur on red raspberries. 

Orange rust...

Question:
How can I control the iris borer?
Answer:

The iris borer is a serious pest of bearded irises.  The mature stage of the iris borer is a grayish moth.  Female moths lay eggs on iris foliage and other nearby plants in late summer/early fall.  The eggs hatch the following...

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