This is the Q&A for the Yard and Garden show for May 15, 2015. Yard and Garden Live is a call-in radio show I do on KUTT 99.5 FM from 10-11:30 am and it will run through July 31, 2015. It can also be found on kutt995.com for online listening. If you missed a show or just want to read through the questions, I have written them all in my blog and will continue to do so throughout the season.
Guest Host: Kevin Korus, Diagnostician for the UNL Plant & Pest Diagnostic Lab
1. A caller with a river birch that is 5-6 years old was planted with 3 trunks and now it has 5 trunks. Should those be removed or will it harm the tree?
A: River birch trees are commonly grown as a multi-trunked tree. If additional trunks appear, they can be left on or cut off with no problems for the tree, as long as they don’t grow too large before they are removed. If the trunks to be removed have grown to be 1/3 of the tree or more or the trunks are 1/2 the size or larger than the main trunk, you would not want to remove these as that would be removing too much of the tree in one growing season and can cause more problems to the tree than benefits. If they are not in the way, I would suggest leaving all 5 trunks.
2. A gentleman wanted to know how and when to prune blackberries and raspberries. He has raspberries that have died from the top downward on some branches with green growth at the base of the plant. What should he do about this?
A: The top dieback would likely be due to water stress or winterkill which occurs during the winter months when we see little moisture. As for general pruning, there is a great guide from the University of Missouri Extension to describe the many practices of pruning brambles, Pruning Raspberries, Blackberries, Gooseberries, Currants, and Elderberries.
3. This caller has amaryllis bulbs that were growing great and now the leaves are starting to turn yellow. What is the cause of this and how can she stop it from happening?
A: This plant is likely in need of a fertilizer treatment. They should receive regular fertilization with a houseplant fertilizer. Also make sure that the plant isn’t sitting in water. Amaryllis plants should be watered when the top two inches of soil are dry to the touch.
4. This caller has Weigela ‘Wine and Roses’ that she had trimmed last fall. Now one of them is only greening up at the bottom of the plant, why is this?
A: This plant is suffering from winterkill. As long as the bottom is greening up, the plant should be fine. Those dead branches can be removed back to green growth or back to the ground if there is no green on the branch at all. Remember to keep plants watered on the warm days when we face a dry winter like we did last year.
5. This caller was curious about rhubarb. How long in the year do you harvest rhubarb in the year or can you continue to harvest all year long? When should they be transplanted? What do you do when seed stalks appear on the plant?
A: You can harvest the plant until the plant begins to produce slender stalks. After that the plant needs to be left alone to replenish the sugars and nutrients to continue growing and produce next year. The stalks can be cut off or they can be pulled off. When the seed stalks appear on the plants, they should be removed. The production of seed stalks takes energy from the plant to make the seeds rather than leaving it to produce leaves and the stalks. Transplanting rhubarb is best done in the spring of the year. Avoid harvesting for the first growing season after transplanting and only do light harvest in the second season. By the third season, harvest can resume as normal. This is to allow the plant to get a good root system developed before loosing much of its leaf area.
6. This caller has a pin oak tree that is 45 years old. He added a mulch ring to the tree recently and wanted to know if rock mulch or wood chip mulch is better for the tree?
A: Any mulch is better than no mulch. Wood chip mulches keep the roots cooler and hold in more moisture than the rock mulches, but the rock mulches will not blow away or need to be replenished each year like the wood chip mulches. Either way keep the mulch only 2-3 inches deep.
7. This caller wanted to know how far apart to plant her asparagus? She planted hers 1.5 feet apart, is this too far apart?
A: Asparagus should be about 6-8 inches deep and 12-18 inches apart. There isn’t a problem with planting it too far apart, the problem would occur if they are planted too close together. Plants not spaced correctly can lead to disease problems.