By James Romer

Horticulturist

Iowa State University Extension

Dear Dr. Grow-It-All,

With October upon us I am faced with the stark reality that I need your help! I couldn’t control myself this spring buying cannas, glads and dahlias in those packages with brightly colored pictures. My hands began to shake as I approached the garden center. I broke out into a cold sweat. My vision became narrowed, but I continued towards the light. Am I having an out-of-body experience? I realized that I had crossed over into another dimension, the PLANT ZONE. As I recovered, I tried to get back to my senses and figure out a financial strategy to pay for everything. I rushed home and threw those plants in the ground. Dr. Grow-It-All, they looked wonderful this year.  However, I am faced with one last chore – digging them up. My back is already hurting and I haven’t started yet. I’m not sure what I need to do with them!

Aching in Payne Junction

Dear Aching,

Tender perennials can have phenomenal displays of vibrantly colored blooms. The downside is that they must be dug and stored indoors to successfully make it though the winter months in Iowa. Hopefully the information below will reward your storage efforts by providing you with viable structures to plant next year after the last average frost date.

Cannas are the easiest of the three to overwinter. Cut the plants back to within 4 to 6 inches of the ground a few days after a killing freeze. The most critical factor in the success or failure of storing canna rhizomes is moisture. If they are packed while still moist or wet to the touch, rotting will occur. Therefore it is best to lift the rhizomes and place in a well-ventilated location to dry for a couple days. Place the clumps in a crate, box, or paper sack. Store the cannas in a cool (40º to 50ºF), dark location and keep them there until danger of frost has passed in the spring. Check the containers periodically though the winter months. Promptly remove any canna rhizomes that are beginning to rot.

Dahlias need a little more attention. After a killing frost has destroyed the foliage, cut off the stems just above the soil surface. Leave the tuberous roots in the ground for 1 to 2 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.  Place the tubers in a well ventilated location for 1 to 2 days so that they feel dry to the touch and cut the stems back to the crown. Place the tubers upside down and cover with vermiculite, peat moss, wood shavings or sand and store in a cool (40º to 50ºF) and dark location.

Carefully dig up the glads after the foliage yellows. Trim off the foliage above the bulb-like corms. Allow the corms to dry for 2 to 3 weeks in a warm (70 to 80°F), dry location.  After drying, remove and discard the dried remains of the old corm located at the bottom of the large, new corm.  Place the corms in mesh bags or other containers that allow for good air circulation. Store the glads in a dry, cool (35 to 45°F), frost free area until they can be replanted the following spring.

Dr. Grow-It-All,

I would like to grow a plant called tulip. I was wondering if you have any advice or if you have heard of such a plant?

Diving In - Spillville

Dear Diving In,

You have come to the right place! Tulips have been popular for many years. 

There are several cultural practices that can help prolong the life of tulip bulbs. Make sure to select the largest bulbs possible. In this case, size does matter. Except for the species tulips, top quality bulbs are 12 centimeters or more in circumference. The larger the bulb, the longer the life of the bulb.

When selecting bulbs, also look to make sure there are no soft spots, blemishes or fungus growing on the bulbs. Tulips perform best in full sun and well-drained soils. Tulips should receive at least 6 to 8 hours of sun. Tulip bulbs decline rapidly in shady locations.  The bulbs often rot in wet, poorly drained locations. Plant the bulbs 6 to 8 inches deep. Planting depth is measured from the top of the bulb to the soil surface. After planting your tulip bulbs, make sure to water them. This enables the bulbs to develop a good root system before winter arrives. October is an excellent time to plant tulips. However, tulips can be planted as late as December if the weather permits.

The care of tulips in spring is also important to their longevity. Be sure to clip the flower heads off in the spring after the blossoms have passed their peak. This prevents the plant from wasting its energy on seedpod formation. Also, don’t disturb the foliage until it dies back naturally. The foliage manufactures food.  This food is necessary to replenish the bulb food reserves. 

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