Tender bulbs for the spring

Canna lilies, dahlias, glads or gladiolas, and tuberous begonias are just a few of the beautiful bulbs we plant in the spring for summer beauty. They are not true bulbs but a collection of rhizomes, corms, and tubers.

I have concentrated on the tender ones because they are the most misunderstood of all the blooming flowers.  They are classed as tender because they must be dug in the fall and saved over winter since they are not winter hardy in our area. These may be considered tender, but they pack a huge color punch in any landscape. I chose a few of the ones that can be over-wintered quite easily with minimum care.

I love the tropical look of the Canna lily. This old favorite has big dark green leaves with a flower scape that opens to big red lily-like blossoms. The older varieties are very tall and can be used to create a tropical feel to the pool area or used as a screen behind shorter plants. There is one variety that has dark mahogany colored leaves. Newer varieties have been developed over the years that can have variegated green with striped leaves, in red and yellow and bright bold orange-red blooms. There are varieties with peach, yellow and bi-colors. Some of the newer varieties are shorter in stature so they can be easily used as a center accent in planters. When you purchase a canna lily, you will see no resemblance to a typical lily bulb.  Cannas are actually rhizomes, and a rhizome is an underground stem.

A rhizome will have growing points or eyes and care must be taken not to damage those funny looking growing points. Plant so that the pinkish growing point is facing up and plant no deeper than 4-6” and about 12” apart. Plant after the danger of frost is over. The rhizomes will continue to grow throughout the growing season.

Tuberous begonias are a perfect plant for a hanging basket or for container gardening. These beautiful begonias grow from a big fat tuber and provide a wide range of colors. When I worked in a garden center, tuberous begonias were sold in thin plastic packs. They were originally propagated from seed. The seeds actually began to form tiny tubers in the cell packs, and you could actually feel the tiny tubers through the thin plastic, if you gently pressed the side! Planting tuberous begonias is easy, and you will have a riot of color throughout the season, if you follow one easy trick. Tuberous begonias have heart-shaped fleshy leaves that come to a distinct point. Plant the begonia so the point is always facing out. The blooms follow the points and grow outwards. This little trick will allow you to have the best floral display of your tuberous begonias. Tuberous begonias will benefit from some shade during the heat of the day.

Dahlias are beautiful and easy to grow. They come in a very tall variety that is often used in competition, with massive dish-sized blooms.  There are also medium-height dahlias that are perfect for cut-flower use.  Both the tall and the medium dahlias make excellent backdrops for other plants in the garden bed. A shorter variety labeled as window box dahlias are perfect for containers. When you purchase dahlias, you are actually buying divisions of the mother plant. Dahlias are an unusual form of tuber. The mother plant forms offshoots that remind me of a hand. Each offshoot has a tiny growing point that becomes a new dahlia plant. Plant all dahlias in the sun.  Large flowering varieties should be planted about 1-3’ apart. Medium varieties are planted at about 1’ apart and the window box about 6” apart. Medium and tall varieties will need staking. A good trick is to use pieces of old nylon stocking for attaching them to the stake, as the stocking will expand as the stem grows and not cut it off. Dahlias are heavy feeders and benefit from addition of fertilizer throughout the growing season. They will benefit from planting indoors about a month before the frost-free date, which in our area is about May 18th.

One of the most beloved of the tender bulbs is the gladiolus or glad. I worked with an elderly man, Herb Janisch, years ago and learned so much about gardening from him. He told the story of how he was ready to plant his gladioli corms and laid them out at the proper planting width while he dug a trench about 3-6” deep, depending on the size of the corms. When he was done with the row, he turned to see his dog had neatly pushed each glad corm into the trench with her nose and all that was left was to back fill over them!  He was so proud of his glad-planting dog!

John and Barb Meyer are growers and hybridizers of gladioli in southern Minnesota. They grow the beautiful flowers for show and for sharing.  They gave me some excellent growing hints. They suggested that you hill the stalks of the glads, much like you do when growing potatoes, with up to 3-6” of soil since the stalks tend to get top heavy and can fall over or break in strong winds. Glads can grow from 3-6,’ depending on variety. If you do not have too many plants, you can choose to stake them.  Use pieces of nylon stocking to gently tie them to the stake. The nylon piece will expand as the stem grows without damaging the stem. The flowers on the glads open from the bottom to the top giving you many days of beauty after cutting. Cut the stalks when one to three flowers have opened. They will continue to open in a vase.

As the growing season moves into fall, it is time to get ready to dig and store your tender plants. Use care when lifting a clump of the plant. Place old screen or hardware cloth on supports. Gently wash the tubers, rhizomes and corms with a garden hose.  Many of the tender bulbs require a curing or drying period. Use that screen and place it in a garage or shed where moisture will not affect the final drying process. The screen allows good air circulation around the entire rhizome, corm or tuber. This whole process should take about three days. Check to make sure that it is nicely dry with no wet spots that will encourage mold and disease.

Carefully lift canna rhizomes with a potato fork when the foliage has died back or is hit by a frost. Gently clean off any old soil and allow to dry completely on the screening material. Most old-time gardeners just put the rhizomes into a clean paper sack and set it in a frost-free part of the basement off the floor.

When dahlias are ready for digging, the whole clump should be lifted, taking care not to injure any of the finger-like projections. The whole rhizome looks very much like fingers attached to the central stalk. The new growing points are located on each individual ‘finger’ near the end that is attached to the faded stalk. Clean the entire clump and allow to cure for about three days. When the main rhizome is dry, cut each individual ‘finger’ taking a bit of the mother stalk with it. Best storage practice is to take some clear cling film and wrap each new rhizome making sure you have labeled the color/variety on either the rhizome or the film. You can make a bundle of the rhizome, making sure there is cling film covering each rhizome as you wrap. Store in a plastic bin off the floor of the basement.

Tuberous begonias, planted in containers, need very little care except to allow the soil medium to dry out and storing the entire container in the basement. If they have been planted as a mass, you can lift the individual tubers and store them in loose peat moss.

Glads are an exception to the timing of lifting. John recommends waiting until 4-5 weeks after blooming, if possible, and before the ground freezes to lift the corms and not wait until the foliage has died back.  Glads form new corm right on top of the old. Smaller corms or cormels may form and may be saved, as they will produce flowers and increase in size two years later. Glads do not require washing, unless you have to dig them from really wet and muddy ground. The corms will need about three weeks to cure and any remaining soil can be gently wiped off. You may wish to remove the old cormel at that time, or you can wait until spring. The best way to store them, according to John and Barb, is in boxes or mesh bags similar to the ones that onions come in and a temp of 35-50 degrees F. It is important to have some air movement around them, so do not cover them.

The tender bulbs are an excellent way to add some beautiful color to your flower garden.  I encourage you to try some this season.


The Drummer and The Wright County Journal Press

PO Box 159
108 Central Ave.
Buffalo MN 55313


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