Spring flowering bulbs such as tulips, daffodils, hyacinths, and crocus should be planted now. This is because that in order for these spring blooming bulbs to flower, they require an 8-14 week chilling period at temperatures 35-40o F. Believe it or not, during this chilling period the bulbs are growing roots.

In North Dakota spring-flowering bulbs can be planted from mid-September until the soil freezes. We want to plant them early so the plant can establish a healthy root system before the ground freezes. This assures a quick start in the spring and bulbs that are well-rooted in fall will be more resistant to possible heaving during winter thaws.

Bulbs should be planted at a depth equal to two or three times their diameter. After planting, roots begin to form immediately. They need water for this process so it important that the soil around the bulbs be moist. This can be achieved by watering the beds to a depth of 6-8 inches. One good soaking is usually enough, unless there is an extended period of hot dry weather.

Although spring flowering bulbs are hardy they often benefit from a 2-4 inch covering of mulch over them once the ground freezes in late fall.

Storing Tender Bulbs for Winter

Summer flowering “bulbs” such as caladium, calla lily, canna, dahlia, elephant ears, gladiolus, and tuberous begonias are considered tender “bulbs” because the fleshy underground storage structures from which they grow will not survive our cold winters. We often refer to these underground structures as “bulbs” however they are not bulbs but rather corms, rhizomes, and tubers. We just use the term “bulb” for convenience sake. At any rate these bulbs are not winter hardy in our area and must be dug in the fall and stored for the next growing season. Since many of these bulbs are expensive it is worth the extra effort required to dig and store them.

These tender bulbs are usually dug after the first frost once the foliage dries up. Bulbs should be dug within a few days of foliage dieback to minimize the entry of rot causing organisms through the now damaged stem.

Dig carefully to avoid cutting or bruising the bulbs as pathogens can readily enter through injured areas leading to rot in storage. A digging fork is less likely than a shovel to cause injury.

As the bulbs are dug, shake off excess soil and cut off the stems leaving about one inch of stem. Allow the bulbs to dry in a well-ventilated area where the temperature is about 60-70o F. Gladiolus and callas need about three weeks of drying time before storage.

The dried bulbs should be stored between 2-3 inch layers of peat moss, sand, or sawdust in a dry location with temperatures between 35-45o F. Ideal storage areas are an unfinished area of a basement away from heat sources, an unheated garage that does not freeze, or a root cellar.

Check the bulbs periodically through the winter and remove any showing signs of rot.

Fall Good Time to Divide Perennials

Another common question I get asked this time of year is, “When should I divide my perennials?” The general rule of thumb is that they should be divided in the season opposite of the one in which they flower. This means that spring-flowering plants should be divided in the fall, and fall-flowering plants should be divided in the spring. Many summer blooming plants can be divided in either spring or fall.

Early spring and fall are the best times for dividing perennials since the weather is cooler and the plants are not using as much water. In spring, plants are divided just as new growth emerges. In fall, plant division is done in late summer or early fall usually about mid-August through early October. Transplanting should be done at least 3-4 weeks before the ground freezes to allow time for the roots to establish. These plants will benefit from being covered with a 4-6 inch layer of mulch to protect against potential winter injury. Mulch should be removed in early April or if there is still snow cover at this time, when snow recedes.

For questions on any of this week’s topics contact Yolanda Schmidt at the Pierce County NDSU Extension office by calling 776-6234 ext. 5.