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Ron Smith answers questions about plants, trees and gardens.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: I have a London plane tree that was planted Dec. 4 by the city Forestry Department. It is 29 degrees with no snow on the ground, but some snow is predicted for later this week. I am concerned about how to care for the tree. I live in zone 6. Should I water it? Will the water freeze around the roots? If so, is that harmful to the tree? Should I compost or mulch it? I would have preferred waiting until spring to plant the tree, but I had no say in the matter. (e-mail reference)

A: The Forestry Department should have provided you with some information. Without knowing your local situation, it is difficult to make recommendations for you to follow. Certainly, the tree should have been watered in. The freezing of the soil around the roots would not have a detrimental effect on the health of the tree. From the standpoint of the tree being planted now, it is successfully done all the time. A common practice in some areas of the country is to purchase living trees and use them for Christmas decorating. After the holiday season, the trees are planted outside. These are evergreens, of course, such as pine, fir and spruce. Every tree I have planted this way has survived. The London plane is a tough tree, so there should be no problem getting it established. I'm just surprised that no guidelines for the tree’s care were given to you by the Forestry Department.

Q: I love your column and use it when I have a question about my gorgeous new garden. I moved from an apartment in California, so it's quite a difference. I planted thousands of dollars worth of bulbs. After only two years, it's a showpiece garden. I just hope I don't choke it out! Here's a question you may want to answer in your column. I'm wintering my dahlia bulbs. I dug them up about a week after the first freeze. I let them dry for a couple of days and layered them in big trashcans between mulch. They are now sprouting in the garage! What should I do? I thought of taking them outside again for a blast of cold, but I’m not sure I should do that. It would be a shame to lose the bulbs because some are the size of salad plates when they bloom. (Boise, Idaho)

A: You started out right, but have them improperly stored. Tubers should be kept in the dark at a steady, cool temperature so they stay firm without rotting, shriveling or sprouting prematurely. The storage place should be dry and above freezing, but below 50 degrees. Aim for 40 to 45 degrees. An old-fashioned root cellar is perfect. Consider an unheated basement, attic, crawl space, attached garage or even a refrigerator. Some gardeners dust their dahlia tubers with powdered sulfur to help prevent rot. The tubers should be stored in paper bags (separately), wrapped in old newspaper or packed in vermiculite. The important thing is to keep the temperature cool, but not freezing and to keep them in absolute darkness. It sounds like your problem is too high a temperature for proper storage. Sort through your tubers and discard those that have sprouted. There is no way you can keep them alive and doing well until next May. Check the tubers as the winter weeks pass to be sure they have not dried to the point of shriveling. If they have, spritz them with distilled water or briefly dip them in it. Allow the tubers to dry for a day before returning them to storage. Good luck!

Q: I just found a huge jade plant that was left in a pile of debris. It weighs about 40 pounds and the trunk at the cut is probably 10 to 12 inches in diameter. Is it possible to replant this thing? I put it in a bucket of water on my way to work this morning, but am afraid I shouldn't have done that. (e-mail reference)

A: I'm assuming that you are referring to just the cut-off plant that you found. If so, temporarily putting it in a bucket of water will keep it from dehydrating, but I doubt that you will be successful in getting the plant to establish as a houseplant because of its size. I suggest taking small stem cuttings from the plant and rooting them in a vermiculite or perlite medium to see if success is possible that way. The size of the cuttings should be 6 to 8 inches. The cut ends should be allowed to dry for about two days at room temperature before sticking them in any kind of medium for rooting. Good luck!

Q: I have a ficus carica in my heated greenhouse in Rhode Island. It is in a large container. During the winter, I keep it at 50 degrees at night, so usually the tree drops its leaves and goes dormant until early spring. It started to produce a nice crop last June, but the fruit fell off before it ripened. This was the first year I left it in the greenhouse during the summer. It gets hot in there in the summer (up to 100 degrees). However, it is dropping its leaves on schedule right now. Do you have any ideas on what I can do to get a good fruit crop? (e-mail reference)

A: I only have known two individuals who successfully have grown this fig in the north. One was in a situation where the tree was buried through the winter and allowed to grow to full fruition outdoors in the summer. It was planted so it had a southern exposure and had a wall behind it to help modulate the temperature. The other case was a situation where they had the tree in a large tub, but the tub was on casters. It was moved inside or outside depending on the season. I think in your case, the tree is experiencing heat stress, so it is dropping fruit. If you could somehow get it up on a dolly or something similar that would allow this kind of movement, I think the fruit would not abort during the summer heat. You also might check with the folks at the University of Rhode Island to see if they have any other or better suggestions. Go to for a contact phone number.

Q: I bought a plant from a grocery store. However, it is in a very tiny pot. I'd like to know when I should replant it and what kind of soil to use. I'd also like to know if you know what kind of soil I should get for my Rex begonia and calathea plants. I also purchased these from my grocery store and they, too, are doing well, but I know they need to be repotted very soon. I have found your advice very helpful, but I just haven't found what I'm looking for. I hope you can help. (e-mail reference)

A: All the plants will need repotting out of their starter pots. There are a number of commercially packaged potting-soil mixtures on the market, such as Miracle-Gro, Black Gold and Hyponex Potting Soil. Most do a more than adequate job. These packaged potting mixes are properly sterilized (or pasteurized) and free from pests, mites and insect larvae. A professionally mixed potting soil for a specific purpose is inexpensive and easy to use. Even professional nurseries use potting soils and mixes blended for them. Every now and then, a batch of the soil misses the pasteurization treatment, so after the plants are repotted, new life in the form of gnats and mushrooms pop up. If you want to be sure it got the treatment, take a cup of the mix out of the bag, give it a little water and allow it to sit for a few days. If nothing is seen flying around the cup, then you are likely in the clear to use the rest of it as you see fit. Some plant varieties, such as African violets, require a soil with a higher percentage of humus (organic matter). At your garden center or the supermarket where you made the purchase, look for special mixes, such as African violet soil, that also can be used with good results on ferns, begonias and other tropical indoor houseplants. If you are up to it, you can come up with your own “designer mix” of sand, loam and humus in equal proportions or in a mixture that provides good drainage. In doing this, you should run about 2 pounds of the final mixture (moistened) through the microwave oven in an open locking plastic bag for about two minutes. This will kill any organisms. Allow it to completely cool before use as a potting mix. Finally, and this is important, put the transplants in a freely draining container. Don't go for the fancy nondraining pots. They look good, but become waterlogged and accumulate salts that affect the growth of the plant. I hope this is the information that you were looking for.

Q: I have just finished the entire section on your Web site about the dreaded poplar tree. I just cut down a big one next to my house. There is one large root running across my yard off the base of the tree, so suckers are a problem. I have been spraying glyphosate on the suckers. That battle seems to be going OK. I'm thinking about digging down to the big root and drilling holes in it to pour rock salt and chlorine tablets in it to kill it. Except for grass, there is nothing else in my yard, so I don't care what I kill around it. I just want the balance of this tree out of my life. Any other ideas or thoughts on how to kill the root system would be appreciated. (e-mail reference)

A: It used to be that I would recommend saltpeter (sodium nitrate) to do the job because it is, in part, a source of fertilizer. However, the product was taken off the market. See if you can find copper sulfate to do the job. It’s used for killing roots that invade sewer lines. Again, this product has fertilizer qualities when diluted enough. However, be careful because it is toxic to plant growth if used in high concentrations. Do what you were planning to do with the chlorine and rock salt. Follow the label directions for dilution and you should be rid of the big root rather quickly.

Q: I recently failed to water two crotons enough, so they started to wilt. I know how to take care of that problem, but what I'm concerned about is the temperature. We live in western Wisconsin and keep our house at 58 degrees to save on heating costs. I noted on your Web site that the temperature for these plants shouldn't dip below 60 degrees. What recommendations do you have to deal with this potential problem? (e-mail reference)

A: We keep our house at 65 degrees so my wife walks around in a snowmobile suit! All the croton plants I have seen have been in similar situations and appear to be doing OK. I wouldn't expect to see much or any growth during the winter months, but it should survive and take off next spring when things warm up again. If you want more security, I suggest a plant light directed right at the plants. That should elevate the temperature sufficiently enough to keep the energy level up in the plant to keep it from getting chill damage. Do you keep yourself wrapped in layers of clothes all the time or have you been toughened up to living at that temperature?

NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161,
Editor:Rich Mattern, (701) 231-6136,
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