Extension News

Digging it with Dr. Grow-It-All

Note to media editors: This is the Garden Column for the week of Oct. 20.


Dear Dr. Grow -It-All;
I planted many tulips two years ago. Recently, I was talking to my mother-in-law and was told that if I don't dig up the bulbs in the fall, all the tulips would eventually produce yellow flowers. Could you tell me is this fact or fiction? The tulips bloomed well this past spring without having been dug up the previous fall. Is this right or am I just…… 

Dreamin' in Beaman


Dear Dreamin';

Read all about it folks -- Fiction, Fiction, Fiction! Ah yes, the insightful wisdom of those who know it all, or at least those who think they do. Tulip bulbs should not be dug up in the fall. The flower color of tulips and most other perennials does not change during their life span. Red flowering tulips will always produce red flowers, yellow flowering cultivars will produce yellow flowers, and so on.


Tulips perform best in well-drained soils in partial to full sun. Plant tulips about 6 inches deep. You can fertilize the bulbs at planting time with a bulb booster, but all the energy for next spring’s bloom is already in the bulb. That is why bulb size is important in this case. The larger the bulb, the more stored energy for a better bloom. Fertilizer can also be applied right after bloom in the spring while the foliage is still green. 


Dear Dr. Grow-It-All;

I was married in May. For a wedding gift, we were given a package of tender perennials. We went on our honeymoon before we opened our gifts. The package sat in our living room for about two weeks before we opened it. My wife and I planted the cannas, glads and dahlias. Despite the delay in opening the gift, we had a wonderful display of flowers. Unfortunately, we didn’t save the box with the instructions of what to do after the growing season ends. Dr. Grow-It-All I’m a little…….

Rocky in Rhodes


Dear Rocky;

Cannas and glads are the easiest of the three to overwinter. For cannas, moisture is the most critical factor in the success or failure of storing the rhizomes. If they are packed while moist or wet to the touch, rotting will occur. Therefore it’s best to lift the rhizomes and place them in a well-ventilated location to dry for one or two days. Then find a paper sack, box or bucket and place the clumps inside. Store the cannas in a cool (40 to 50 degrees F), dark location and keep them there until the danger of frost has passed in the spring. Periodically check the containers during the winter months to make sure none of the rhizomes have rotted.


After glad foliage yellows, carefully dig up the plants, then trim the foliage to within 1 to 2 inches of the bulb-like corms. Allow the corms to dry for two to three weeks in a warm (70 to 80 degrees F), dry location. After drying, remove and discard the dried remains of the old corm located at the bottom of the large, healthy corm. Place the corms in mesh bags or old nylon stockings. Store the glads in a dry, cool (35 to 40 degrees F is ideal), frost-free area until replanting in spring.


Dahlias need a little more attention. After a killing frost has destroyed the above ground foliage, cut off just above the soil and let the tuberous roots sit in the ground for one to two weeks. This gives the roots a chance to cure before their removal from the soil. If the cultivar name is important, write the name of each plant on a tag or label before digging the dahlias. They all look similar after being dug.


Using a spade or potato fork, carefully lift each clump out of the ground and immediately attach its identification tag to one of the tubers. Next, wash off as much of the soil as possible. Allow the tubers to dry to the touch (usually one or two days), and then cut the stems back to the crown. Place the tubers upside down in a box or some other container and cover with vermiculite, peat moss, wood shavings or sand and store in a cool (40 to 55 degrees F ideal) and dark location.




Contacts :

James Romer, Horticulture, (515) 294-2336, jromer@iastate.edu

Jean McGuire, Extension Communications and Marketing, (515) 294-7033, jmcguire@iastate.edu

There are no photos for this week's column.