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WCCO Radio "Smart Gardens" Q&A - September 13, 2014

Thanks for listening!

We aren't always able to answer everyone's texted questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources.

Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

Question: Paver stone patio on north side of house has mold / moss in between stones. How do I get rid of this?

Answer: You can use a sharp tool to scrape / dig out moss and fill in spaces with builders' sand. You can plant low-growing, creeping plants like creeping thyme or wooly time in the spaces.
Mold can be removed with a bleach / water solution and a wire brush. Be careful not to get bleach on the plants nearby, your clothing or patio furniture.
Question: I just planted a 2" Autumn Blaze maple. What are you recommendations for watering?

Answer: Here is an excerpt from the U of M Extension publication Planting and Transplanting Trees and Shrubs (Gillman et. al):
Newly planted plants require routine watering. Typically, 5-7 gallons, applied to the root ball once a week, is an appropriate quantity of water to add to a newly planted tree or shrub; however, differing soil and weather conditions will affect the frequency with which water must be added. Examine the soil moisture 4-8 inches deep to determine the need for water. If the soil feels dry or just slightly damp, watering is needed. Soil type and drainage must also be considered. Well-drained, sandy soil will need more water, and more often than a clay soil that may hold too much water. A slow trickle of the garden hose at the base of the plant for several hours or until the soil is thoroughly soaked is the best method. Short, frequent watering should be avoided as this does not promote deep root growth but rather, the development of a shallow root system that is vulnerable to several environmental stresses.

Be sure to consult this publication for additional information about planting trees.

Question from Anne in Apple Valley: On my 'William Baffin' roses, the leaves turned yellow with brown spots, then dropped. Bare canes are still green. Is this fungal and should I treat before winter? Should I prune the canes back to the a foot from the ground and clean up to try and avoid re infection next spring? These are large 7- yr old plants and don't want to lose them.

Answer: It sounds as though your rose has black spot. Here is a good publication Rose Diseases (Pfleger et. al). Black spot on rose is a fungal disease caused by splashing water onto leaves. We had a rainy spring and summer and thus this was a "good" year for such diseases. Note that sanitation is a good place to start in reducing the occurrence next year. Treatment occurs during the growing season when the first signs of the disease occur. It is not appropriate to treat now. Diseased canes should be cut back a few inches into healthy wood. You can also help reduce water droplets that can foster fungal spores by watering at the base of the plant and mulching the roots. Space out the canes as you tie them to your trellis / fence so air can circulate, drying off leaves and canes.

Question: Should a Fat Albert spruce be fertilized now?

Answer: Stop fertilizing trees and shrubs in mid-summer. Fertilizing now will cause new growth to occur that can be damaged by cold temperatures. Water evergreens now up until you cannot water any longer. This will reduce the chance of desiccation and browning of needles. More on evergreens

Question: Can I prune the water shoots off my crab apple now? How often can we prune to preserve size and shape?

Answer: Crab apple trees should be pruned once a year in late winter while still dormant. This will reduce infestations by pests and all the plant to heal the cut wound more quickly when it begins actively growing in early spring. Remove water shoots and selectively prune branches to open up the canopy, allowing air and light to reach the inner branches and buds. Protect the tree from animal damage in the winter by surrounding the trunk with hardware cloth fencing or corrugated plastic tubing. More on pruning trees.

Question: How do I know when to re-pot a ZZ plant?

Answer: Zamioculcas zamiifolia or "ZZ plant" is not one of the plants I know well, I admit. After some reading, I found out it is a rainforest plant, but has about 3-4 months of dry conditions. The plant apparently does not do well when pot-bound / crowded; hence, it may stop developing new leaves and stems. That may be the indicator that it's time to re-pot. It is apparently an excellent houseplant that grows well indoors and has few if any pest issues. It may drop its leaves once a year and appear dead, but that is apparently just its dormant behavior. Soil should be well-drained. It does not need much fertilizer - either a slow release balanced fertilizer every three months or a very dilute liquid fertilizer (1/4 strength) when you water.
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