Frequently Asked Questions

Question:
When can I start harvesting newly planted rhubarb?
Answer:

After planting rhubarb, it’s best to wait 2 years (growing seasons) before harvesting any stalks.  The two year establishment period allows the plants to become strong and productive. 

Rhubarb can be harvested over a 4 week...

Question:
What should I look for when buying annual flower and vegetable plants?
Answer:

Select short, stocky plants with dark green foliage.  Avoid tall, spindly plants.  Small to medium-sized transplants become established in the garden more quickly than large ones.  Short, stocky vegetable transplants are often more...

Question:
Do annual flower and vegetable plants need any special care before planting?
Answer:

Annual flower and vegetable plants started indoors or purchased from greenhouses should not be planted directly into the garden.  The intense sun and strong winds may damage or kill the tender transplants.  Plants should be “hardened” (...

Question:
What is the proper way to plant annual flower and vegetable plants?
Answer:

Carefully remove plants from plastic cell packs by gently squeezing the bottom on each compartment.  Plants in plastic pots can be removed by tipping them on their sides and tapping the bottom of the pots.  

If possible, plant...

Question:
How do I lower the soil pH for blueberries?
Answer:

Home gardeners can lower their soil pH by adding sphagnum peat moss to the soil.  Sulfur can also be used to acidify the soil.  Sulfur should be incorporated into the soil a year before planting as it reacts slowly with the soil. ...

Question:
How do you plant blueberries?
Answer:

Early spring is the best time to plant dormant, bare-root blueberries.  Soak the roots of bare-root plants in water for about an hour before planting.  Prune back the plants by half by removing the small side branches and by heading...

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

Early spring (late March to early May) is the best time to plant strawberries in Iowa. 

Question:
Can bush cherries be grown in Iowa?
Answer:

Bush cherries are very cold hardy and can be grown throughout Iowa.  Bush cherries include Nanking cherry (Prunus tomentosa), Hansen’s bush cherry (Prunus besseyi ‘Hansen’s), and several cherry hybrids.  Their fruit...

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:
When can I plant tuberous begonias outdoors?
Answer:

Plant tuberous begonias outdoors after the danger of frost is past. In central Iowa, mid-May is an appropriate planting date.  

Plants started indoors or purchased at a greenhouse should be hardened outdoors 7 to 10 days before...

Question:
What type of planting site do tuberous begonias prefer?
Answer:

Tuberous begonias perform best in moist, well-drained soils in partial shade.  Choose a site sheltered from strong winds.  In the home landscape, locations that receive morning sun and afternoon shade are often excellent planting sites...

Question:
Which evergreen trees perform well in home landscapes in Iowa?
Answer:

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...

Question:
Which perennials grow well in dry soils?
Answer:

Perennials that tolerate dry soils include yarrow (Achillea spp.), wormwood (Artemisia spp.), butterfly weed (Asclepias tuberosa), false blue indigo (Baptisia australis), threadleaf coreopsis (Coreopsis...

Question:
Can azaleas and rhododendrons be successfully grown in Iowa?
Answer:

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...

Question:
What are suitable planting sites for azaleas and rhododendrons?
Answer:

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...

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 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:
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 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...

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