Extension News

Ask the ISU Expert

Orange Dahlia

Note to media editors:

Got gardening questions? Contact the Hortline at (515) 294-3108 (M-F; 10-12 & 1-4:30) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu


When should I plant potatoes in the garden?   

Potatoes should be planted in early spring. Appropriate planting times are 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. 


Since potatoes are susceptible to several diseases, buy certified, disease-free potatoes at garden centers or mail-order nurseries. Gardeners can purchase seed pieces (tubers that have been cut into sections) or whole potatoes. Small potato tubers may be planted whole. Large potatoes should be cut into sections or pieces. 


Each seed piece should have 1 or 2 “eyes” or buds and weigh approximately 1.5 to 2.0 ounces.  After cutting the tubers into sections, place the freshly cut seed pieces in a humid, 60 to 70 degrees F location for 1 or 2 days. 


A short “healing” period allows the cut surfaces to callus or heal over before the seed pieces are planted.  Healing of the cut surfaces helps prevent the rotting of seed pieces when planted. 


Plant seed pieces (cut side down) and small whole potatoes 3 to 4 inches deep and 1 foot apart within the row.  Rows should be spaced 2.5 to 3 feet apart.  


The flower and vegetable plants that I start indoors get tall and spindly.  Why?   

Tall, spindly growth is a common problem when growing transplants indoors. Poor (insufficient) light, excessive watering, high temperatures, excessive fertilization and crowded conditions are factors which contribute to spindly growth. 


Proper growing conditions should produce short, stocky transplants.  Immediately after germination, move the seedlings to an area with a temperature of 60 to 70 degrees F and place them under fluorescent lights. (A sunny window often doesn’t provide sufficient light.)


A standard fluorescent shop fixture containing two 40-watt tubes (one cool white and one warm white) works fine. Position the fluorescent lights no more than 4 to 6 inches above the seedlings.  Leave the lights on for 12 to 14 hours a day.


Thoroughly water the seedlings when the soil surface becomes dry to the touch. Fertilize every 10 to 14 days with a dilute fertilizer solution. Seedlings growing in flats should be transplanted into individual containers when the first “true” leaves appear. 


When should I start dahlias indoors? 

To promote early bloom, start dahlia tubers indoors in early April.  Fill an 8-inch-diameter pot approximately three-fourths full with potting soil, place the tuber horizontally on the soil surface, then cover with an additional 1 or 2 inches of potting soil. Water thoroughly. When growth emerges, place the dahlias in a sunny window or under artificial lighting. 


Dahlias can also be grown from seeds. Sow seeds indoors 10 to 12 weeks before the date of the average last spring frost. 


Plant dahlias outdoors after the danger of frost is past. Before planting, harden or acclimate the dahlias to outdoor conditions for several days. Initially place the dahlias in a shady, protected location. Then gradually expose the plants to longer periods of sun. 


Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

There are two high-resolution photos suitable for printing available for use with this week's column:

Orange dahlia (thumbnail image above), dahlia3-8-06.jpg, 900K file

Seed potatoes, potato3-8-06.jpg, 1.25MB file