Ask the ISU Extension Garden Experts

When can 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 one or two “eyes” or buds and weigh approximately 1.5 to 2 ounces. After cutting the tubers into sections, place the freshly cut seed pieces in a humid, 60 to 70 F location for one or two 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 1/2 to 3 feet apart.

Should I apply lime to my garden?  

In Iowa, gardeners should apply lime to gardens and lawns only when recommended by a soil test. A soil test will indicate the current soil pH and, if necessary, the amount of lime to apply to the area. Liming materials include ground limestone, which is mainly calcium carbonate (CaCO3), and dolomitic limestone, which contains calcium carbonate and magnesium carbonate (MgCO3). 

Lime is applied to acidic soils to raise the soil pH. The soil pH is important because it affects the availability of essential nutrients. The pH scale runs from 0 to 14. Any pH below 7 is acidic and any pH above 7 is alkaline. A pH of 7 indicates a neutral soil. The optimum pH range for most flowers, vegetables and other horticultural crops is between 6 and 7. Lime is applied to acidic soils with a pH below 6 to raise the pH into the optimum range.  However, an application of lime to an alkaline soil can raise the soil pH to excessively high levels, reducing the availability of plant nutrients and leading to poor plant growth.

How do I have my garden soil tested?  

Soil testing is done by private and state laboratories. View instructions for submitting soil samples to the Iowa State University Soil and Plant Analysis Laboratory.

Richard Jauron , Horticulture, (515) 294-1871,
Willy Klein, Extension Communications and External Relationsh, (515) 294-0662,