Frequently Asked Questions
The hair-like growths are likely galls. Galls are abnormal growths of plant tissue induced to form by mites, insects, or other small organisms. The hair-like gall on the maple leaves is probably the maple spindle gall.
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The leaf drop is probably due to apple scab. Apple scab is a fungal disease caused by the fungus Venturia inaequalis. Cool, wet weather in spring favors apple scab development. Crabapple varieties differ in their susceptibility to apple...
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...
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...
Only a small number of evergreen trees perform well in Iowa. Some evergreens, such as Scotch pine and Austrian pine, have serious disease problems and are no longer recommended for planting in Iowa. The most reliable evergreens for...
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...
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...
Perennials that tolerate dry soils include yarrow (Achillea spp.), wormwood (Artemisia spp.), butterfly weed (Asclepias tuberosa), false blue indigo (Baptisia australis), threadleaf coreopsis (Coreopsis...
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...
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...
The white, fuzzy objects on the branches of your maple tree are wooly alder aphids. (The insect is also known as the maple blight aphid.) Wooly alder aphids feed on the sap of maple trees from bud-break until late June. Then...
Which azaleas can be successfully grown in Iowa?
Azaleas in the Northern Lights Series possess excellent cold hardiness and perform well in Iowa. (The Northern Lights Series is a group of hybrid azaleas developed and released by the University of Minnesota. All cultivars in the series...
The most widely grown rhododendrons in Iowa are the Weston hybrids. Introduced by the Weston Nursery in Massachusetts, these cultivars possess excellent cold hardiness. Weston hybrids include ‘PJM’ (lavender pink flowers), ‘PJM...
There are more than 900 species and innumerable cultivars of azaleas and rhododendrons. However, only a small number perform well in Iowa. To be successful, the Iowa gardener must select cold hardy cultivars, choose suitable planting...
Proper site selection is important when planting azaleas and rhododendrons. Azaleas prefer partial to full sun. Rhododendrons perform best in protected sites in partial shade. Areas that receive morning sun and afternoon shade...
Everbearing and day-neutral strawberries should not be renovated like June-bearers. Everbearing and day-neutral strawberries are most productive when the plants are maintained as large, single plants. All runners that develop on...
Annual grasses, such as crabgrass and foxtail, can be controlled by hand pulling.
Perennial grasses, such as quackgrass, are much more difficult to control as they spread via underground stems or rhizomes. (All of the rhizomes...
Newly planted rhubarb will initially produce small, spindly stalks during its 2 year establishment period. The stalks of large, old plants may be small and spindly because of overcrowding. Poor plant vigor due to poor cultural...
The best time to divide perennials varies with the different plant species. Early spring (just as new growth begins to appear) is the best time to divide aster, chrysanthemum, hosta, bee balm, sedum, yarrow, obedient plant, and ornamental...
Plants in containers need to be fertilized on a regular basis as nutrient levels in potting mixes quickly fall due to absorption by plants and leaching during watering.
Many commercial potting mixes contain a slow release fertilizer...
Deadheading is the removal of spent flowers. While tulips should be deadheaded immediately after flowering, it is not necessary to deadhead daffodils. The vigor of tulip bulbs quickly declines if tulips are not promptly deadheaded and...
Chrysanthemums perform best in moist, well-drained soils. Avoid wet, poorly drained sites. Improve hard, difficult-to-work soils by incorporating 2 to 3 inches of organic matter, such as compost, peat, or barnyard manure, into the...
Fruit trees purchased from nurseries and garden centers are usually 1- to 2-year-old plants. The length of time from planting to fruit bearing varies with the species of fruit, the cultivar, and whether the tree is dwarf or standard....
Annuals that can be successfully grown in shady areas include wax begonia (Begonia x semperflorens-cultorum), impatiens (Impatiens walleriana), lobelia (Lobelia erinus), coleus (Solenostemon...
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