Frequently Asked Questions

Question:
How do I lower the soil pH for azaleas and rhododendrons?
Answer:

Home gardeners can lower their soil pH by adding sphagnum peat moss to the soil.  (The pH of sphagnum peat moss generally ranges from 3.0 to 4.5.)  When planting azaleas and rhododendrons, dig a wide, shallow hole.  Backfill with a...

Question:

Which azaleas can be successfully grown in Iowa?
Answer:

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...

Question:
Which rhododendrons can be successfully grown in Iowa?
Answer:

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...

Question:
Why are my rhubarb stalks small and spindly?
Answer:

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...

Question:
What is a suitable planting site for tomatoes?
Answer:

Tomatoes perform best in fertile, well-drained soils.  Avoid heavy clay soils and poorly drained sites.  For best yields, tomatoes need at least 6 hours of direct sun per day.  To discourage Septoria leaf spot, early blight, and...

Question:
When should I divide my perennials?
Answer:

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...

Question:
Can I successfully sow grass seed after the application of a preemergence herbicide?
Answer:

Preemergence herbicides, such as benefin, bensulide, and pendimethalin, prevent the germination of crabgrass seeds in spring.  Most preemergence herbicides also prevent the germination of turfgrass seeds.  If you intend to sow grass...

Question:
What would be a good planting site for asparagus?
Answer:

Carefully consider possible planting sites as asparagus is a perennial crop.  A well maintained asparagus planting may be productive for 15 to 20 years.  

Asparagus performs best in well-drained soils in full sun.  Planting...

Question:
What is the proper way to plant onion seeds?
Answer:

Plant onion seeds as soon as the ground can be worked in spring (late March or early April in southern Iowa, early to mid-April in central Iowa, and mid to late April in northern portions of the state).  Plant seeds in rows 12 to 15 inches...

Question:
What is the proper way to plant onion plants?
Answer:

Plant onion plants from early April to early May.  Place plants 1 to 1½ inches deep in rows 12 to 15 inches apart.  To produce large, dry onions, space plants 2 to 3 inches apart. 

Question:
What is a good planting site for onions?
Answer:

Onions perform best in well-drained, slightly acidic, fertile soils in full sun.  The planting site should receive at least 6 hours of direct sun each day.  Heavy soils can be improved by incorporating organic matter, such as compost,...

Question:
My red raspberries are spreading rapidly. What should I do?
Answer:

Red raspberries spread rapidly as they sucker profusely from their roots.  To prevent the planting from becoming a wide, unmanageable thicket, red raspberries should be confined to a one- to two-foot-wide hedgerow.  Shoots growing...

Question:
What would be a good planting site for butterfly weed?
Answer:

The butterfly weed (Asclepias tuberosa) is a member of the milkweed family.  Plants grow 2 to 3 feet tall and produce flat-topped clusters of bright orange flowers from July through September.  Their flowers attract several...

Question:
Where should the pruning cut be made when removing a branch?
Answer:

Cut off the branch just beyond the branch collar and branch bark ridge.  The branch collar is the swollen area at the base of the branch.  The branch bark ridge is the dark, rough bark ridge that separates the branch from the main...

Question:
Which shrubs grow well in dry sites?
Answer:

Deciduous shrubs that grow well in dry locations include Siberian peashrub (Caragana arborescens), American hazelnut (Corylus americana), cranberry cotoneaster (Cotoneaster apiculatus), hedge cotoneaster (...

Question:
Which trees grow well in dry locations?
Answer:

Deciduous trees that grow well in dry sites include northern catalpa (Catalpa speciosa), hackberry (Celtis occidentalis), Turkish filbert (Corylus colurna), thornless honeylocust (Gleditsia triacanthos var....

Question:
Is it necessary to deadhead daffodils?
Answer:

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...

Question:
What would be a good planting site for chrysanthemums?
Answer:

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...

Question:
When is the best time to plant rhubarb?
Answer:

Spring is the best time to plant rhubarb in Iowa.  Plants can be purchased at garden centers or from mail-order catalogs.  Digging and dividing large existing plants is another source of plants.  

Plants growing in...

Question:
What are cornelian cherries?
Answer:

The cornelian cherry (Cornus mas) is actually a species of dogwood.  It is also referred to as cornelian cherry dogwood.  The cornelian cherry dogwood is an adaptable, durable, and relatively pest-free small tree.  Plants...

Question:
What are honeyberries?
Answer:

Honeyberry (Lonicera caerulea) is a species of honeysuckle native to cold regions of Europe, Asia, and North America.  Other common names include blue honeysuckle or haskap.  Honeyberries grow 4 to 6 feet tall.  Plants...

Question:
What are serviceberries?
Answer:

Serviceberries are members of the genus Amelanchier.  Other common names for plants in the genus Amelanchier include juneberry, saskatoon, shadbush, sarvisberry, and sugar plum. 

Serviceberries are dual-purpose...

Question:
My Japanese spireas are straggly in appearance. How should I prune them?
Answer:

Japanese spireas (Spiraea japonica) are small shrubs that grow 2 to 3 feet tall.  Plants produce clusters of small pink flowers in summer.  Numerous cultivars are available.  The best way to renew or rejuvenate straggly...

Question:
How should I prune my hydrangeas?
Answer:

Three species of hydrangea are commonly grown in Iowa.  Pruning practices are based on the flowering characteristics of each species.  

The smooth hydrangea (Hydrangea arborescens) grows 4 to 5 feet tall.  Smooth...

Question:
How soon will a newly planted fruit tree begin to bear fruit?
Answer:

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....

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