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Don Kinzler, Published February 10 2012

Twice-a-week watering too much in winter

Q: I had nine dogwoods professionally planted in December. They obviously are dormant (no leaves, just buds). The company did a great job treating the soil and placing mulch around the trees. The company recommended I water each tree twice a week for 10 minutes. I worry about causing rot, which will allow fungus and worms to attack because our soil has so much clay in it.

If the landscaping company watered the trees when they were planted and we have had some rain during the last month, do I need to water these trees during their dormant period? If so, for how long? I want to do the best I can to keep these trees alive because they were planted in memory of my father and are my favorite type of tree. (Memphis, Tenn.)

A: Twice a week is too much during the winter dormancy months in your part of the country. Generally, deciduous trees and shrubs do not need much water beyond the good watering they received after planting. The organic mulch the landscapers applied will keep the root area moist enough that you shouldn’t have to worry about watering again until or unless there is an extended dry spell during the winter months, such as two to three weeks with no precipitation. I don’t know why some landscape companies make blanket recommendations like this.

Watering twice a week for 10 minutes could threaten the survivability because of oversaturation of the root area. The best advice is to water it in thoroughly right after planting and monitor the soil moisture after that. Water in response to how much rain you get.


Q: I bumped into a woman in the lobby of my condo who was about to throw out a gorgeous schefflera. I quickly said I would take the plant. It seems healthy, but there are a few things I am a bit concerned about. There is a white, crusty surface covering part of the top layer of soil and it has an ammonia smell to it. I’m not sure what that is or if it might be dangerous for my other plants. Is it a fungus?

Two small branches are yellow. I believe this is due to the branches not getting enough light, but I’m not sure. Should I remove the two stems or will they turn green with proper lighting? I also noticed there are bumps on most of the thicker stems. The bumps can be removed if you rub the stem with your finger or pick at them. I see a bit of sap coming out of some of the stems, but only the stems that have been pruned. Should I be worried about the sap?

I understand that schefflera plants are poisonous, but you do not classify it as a poisonous plant. Could you explain your reasoning? I notice that some of the leaves are curled, which I believe is due to the plant not getting enough water. I did not do anything to the plant last night because I figured it had enough shock for one day. I did give it a lot of water today. So far, the plant has not responded to the additional water. I put the plant close to the windows of my east-facing condo. (Toronto)

A: The white stuff on top of the soil could be a saprophytic mold or salt accumulation. I suggest that you repot the plant using an all-purpose potting soil and also get a new pot that drains well. Cut back the yellow foliage and remove the bumps if you can. What you have on the plant is a scale infestation that will get worse. If there are an overwhelming number of them, it might be the reason the previous owner was going to dump the plant. The infestation can spread to your other plants. Schefflera plants are not poisonous. The plant is not listed as poisonous in any poisonous plant documents. The sap you see is a skin and mucus membrane irritant, so contact with the skin should be avoided if at all possible. Perhaps other sources consider anything poisonous that causes skin irritation.

If you choose to keep the plant, which I don’t recommend, be sure to mist it while you are using your central heating system during the winter months. Scale will show up during warm and dry conditions. I hope this information helps. My advice in the future is to question why someone is giving up on a particular plant. They usually have a good reason for doing it.


Q: I hope to get a little advice from you about lighting and spots on my fig tree. I just bought the tree and it looks great. However, I am worried about the amount of light in my apartment. Right now, the tree gets about seven hours of indirect sun from the west. There is a building behind my apartment, so the lighting is limited. I can move the fig tree to a brighter spot, but there are heaters under all the windows. Do full-spectrum bulbs work as grow lights? Are the brown spots on the tree a sign of poor lighting? Thank you in advance and I enjoy your Hortiscope column. (Brooklyn, N.Y.)

A: The spots mostly are a reaction to a winter environment of humidity down to 10 percent or less at times. Fig trees and other tropical plants are at home in a high-humidity environment. When the tropical plants are confronted with dry air and low light, problems start showing up. You never will cure what damage already has taken place. The plant does its own thing at compartmentalizing problems such as this. Get a grow light and set the timer for 14 hours of continuous light. I also would advise misting the tree with distilled water on a daily basis while your heating system is active.


Q: I have a prickly pear and mammillaria cactus that appear to be dying. I’m not sure if I’m overwatering or underwatering the plants. I live in New Jersey, so they are growing inside the house. I water them once a week in the summer. I’m trying to refrain from watering so often, so I water them now about once a month. The prickly pear seems a little soft and is starting to bend over. On the mammillaria, I trimmed off one shoot and cut it open. The tissue inside is practically gone, so it is hollow and there is some thick liquid coating the side of the skin. I’ve heard that some cacti and succulents can go dormant and look dead during the winter. How can I tell if a plant is going dormant or dying? Is there a better way to water a cactus so that it won’t get waterlogged?

How much water do I give the plants each time and how often? Thanks for your help. (email reference)

A: Your cacti are on the way out based on your description. Dormant cacti don’t become what you are telling me. The watering question is a popular and impossible one to answer. I get the question on trees, shrubs, flowers, vegetables, new lawns and, of course, houseplants. With cacti, the media has to dry out completely before watering. How often and how much to water depends on some variables. The variables include type and size of the container, light exposure, how well the soil drains, air temperature, humidity and the quality and temperature of the water being used. Proper watering comes from learning about these factors and a generous dose of common sense. The two most common causes of houseplant death are overwatering and insufficient light.

Consequently, when I get questions about why a particular houseplant is dying, the answer usually comes back to one of the two factors I just mentioned.

Amazingly, the answer comes as a surprise to most people. Don’t take this as a personal lecture, but it’s something to think about for you and everyone else who will read this response.


To contact Ron Smith for answers to your questions, write to Ron Smith, NDSU Department of Plant Sciences, Dept. 7670, Box 6050, Fargo, ND 58108-6050 or email ronald.smith@ndsu.edu.