Q. I have been collecting red and orange Canna seeds this year from plants produced by bulbs at least 3 years old. Can these seeds be propagated? If so, what steps should I take?
A. Canna is more typically propagated by dividing the rhizomes (thick, underground stems) so that each new section has at least one healthy bud that will become the new shoot. They can be propagated by seed, but keep in mind that the seedling offspring will vary considerably in their flower and foliage color, height and size of bloom, etc. The fancier the bloom, the less likely its seed will come true.
Most canna seed have a very thick, hard seed coat that needs scarification (abrasion and/or softening) before the plant embryo can emerge. The seed will have a scar on one edge where the embryo’s shoot will eventually emerge. Using sandpaper, rotary sanding band or a file, remove a little bit of the seed coat on the side opposite the scar, erring on the side of filing too little rather than too much. Some gardeners find it helpful to then soak the seed in warm water overnight. Then place in potting soil, moisten and place in a warm, 70-degree F location. Once the shoot has emerged, place in a sunny, warm location until they can be transplanted outdoors after last frost.
Q. We recently moved to a new location with a lovely row of asparagus. Can you help us with info on its culture?
1. Weed control — what herbicides will it tolerate?
2. Fertilizer
3. Mulch
4. Winter preparation
A. Asparagus is fairly easy to grow, likes a more alkaline soil than most other vegetables and, of course, is a perennial plant that dies back to the ground each year, but re-grows new stalks each year. These young tender stalks in spring are what we harvest. Mulch may help keep some weeds under control, but inevitably some additional weed control will be needed. This subject was recently discussed in the following column: http://www.hort.purdue.edu/ext/ITG_nov08.html.
Additional information on fertilizing and mulching can be found in Purdue Extension Bulletin HO-96, http://www.hort.purdue.edu/hort/ext/Pubs/HO/HO_096.pdf.
Q. I have, what I have been told, are Autumn Clematis vines on my clothesline posts, which I don’t use anymore. How should these plants be taken care of? I was told to cut them back to within 18 inches of the ground. Is this correct? How long will it take for them to grow back? There is a trellis on each post & they are completely covered and started down the clotheslines.
A. Ah, beauty is in the eye of the beholder with this plant! Sweetautumn clematis, (Clematis terniflora) is a vigorous (often rampant!) spreading vine, with loads of fragrant white flowers in late summer or early fall. The plant dies back to the ground each winter, and grows new stems each spring and flowers on this new growth. The plant seems to thrive on neglect, so would not need to be cut back at all, but can (should) be cut back to about 2-3 feet any time after the stems have died back and before new growth begins in the spring. Sweetautumn clematis spreads both by seed and roots, and once established is difficult to get rid of. So depending on the situation, it can be a welcome, old-fashioned garden flower or an invasive uninvited “guest.”