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Ask the Master Gardener: Oleanders can be houseplants, but be wary of their toxicity

Eating even small amounts of any part of the plant can cause a person or animal severe illness and even death.

An oleander plant. Contributed / Jennifer Knutson

Dear Master Gardener: My sister-in-law gave me an oleander tree in a container at the beginning of the summer. It is so beautiful I would like to try to keep it as a houseplant? When should I bring it in and how should I care for it over the winter?

Answer: Oleander plants are hardy to zones 8b-10, so technically they can survive temperatures as low as 20 degrees. I’ll be bringing mine in when nighttime temperatures start hitting 50 degrees. If your plant has gotten too large you can prune it back when you bring it in — just make sure to wear gloves when pruning it because the sap can cause severe irritation. Keep your plant in a fairly dry and cool location (basement). Like many plants it goes into a resting period during the winter, so it doesn’t need much water and shouldn’t be fertilized. After February, start increasing water and light, but don’t fertilize it until you are ready to take it outside. When there is no danger of frost (usually the end of May), start gradually acclimating your plant to the outdoors. Oleander is extremely toxic! Eating even small amounts of any part of the plant can cause a person or animal severe illness and even death.

Related: Ask the Master Gardener: Gardeners experiencing common tomato disorders
Dear Master Gardener: I have white balls of fungi that range in size from golf balls to tennis balls. They have a mushroom texture. Is this a sign of something bad?

A reader of Ask the Master Gardener sent this photo of a puffball mushroom. Contributed


Answer: These white fungal spheres you have in your lawn are called puffballs. They can range in size from golf balls to watermelons. Don’t worry, they are not a sign of something bad and are not harmful to people or pets. In fact, some puffball mushrooms are edible while the inside is still white and fleshy. I don’t recommend sautéing them and putting them on your steaks unless a mushroom expert identifies them for you. The only way to get rid of them is to remove the mushrooms as they appear.

Related: Ask the Master Gardener: It's easy to save seeds for use next year
Dear Master Gardener: The deer ate my lilies before they had a chance to bloom, so I am going to move them to a “safer” area. How and when can I move them?

Answer: It would be best to wait until it is a little cooler, but if you want to move them now, do it on an overcast or cooler part of the day. Carefully dig up the entire clump, making sure to get several inches under the bulbs to avoid disturbing the stem roots. If you don’t expose the bulbs and roots to air, they will never know they were moved to a new location!

Related: Ask the Master Gardener: Planting proper plants for monarch butterflies
Dear Master Gardener: I think we have buckthorn. Is there a trick to identifying it and if we have it how do we get rid of it?

Answer: Buckthorn is one of Minnesota’s most aggressive, damaging, invasive plants. There are two different species of buckthorn and they are both listed as restricted noxious weeds in Minnesota. According to the U of M, the key identifiable feature of this plant is the “buck hoof print” that can be seen at the end of the twig. This hoof print is formed by two terminal buds and a thorn going down the middle. Buckthorn leaves are some of the last to drop in the fall, which helps the homeowner identify it more easily among the understory shrubs in their woods. When controlling buckthorn, the female plants should be eradicated first because they produce berries with seeds that birds and other wildlife scatter and spread. If you have small seedlings, they can be pulled by hand or with tools. Another option is mowing to reduce vegetation or doing a combination of mowing with chemical treatments on the resprouts. If you have large diameter stems, cut them down with a chainsaw and brush an herbicide on the exposed stems. The U of M recommends using herbicides with glyphosate or triclopyr for buckthorn control. Apply the herbicide on the tree stumps with a paintbrush, dauber, or low volume sprayer by covering an inch in from the edge of the outer bark. The center of the stem does not have to be treated. Two other options for treatments from the U of M are as follows:

  • Herbicide can also be applied directly to the bark using a basal bark treatment. This treatment works well for trees up to 5 inches in diameter. From the ground level up to 18 inches above the ground, wet the area with a low-volume sprayer.

  • Foliar applications are effective for smaller buckthorn plants. Spray buckthorn leaves until wet. The water-based formulation of triclopyr works well for foliar applications, but will drip and kill anything growing underneath as well.

When using herbicides always follow the directions on the label, wear protective clothing, and avoid contact with non-target plants.
Related: Ask the Master Gardener: Curcuma plants can offer a spectacular display
Dear Master Gardener: My coneflower plants have weird-looking, deformed flowers. Is this some kind of disease?

Answer: Unfortunately, it sounds like your coneflowers have a disease called aster yellows. Aster yellows tend to be more prevalent during hot years, which explains why you are experiencing it this year. It spreads by leafhoppers, so you will need to remove the infected plants right away. If some of your plants are not showing symptoms, you don’t have to remove them, but keep an eye on them. Remove any that start showing symptoms. Do not put infected plants in your compost.

Related: Ask the Master Gardener: Tips for fending off a garden-destroying fiend


You may get your garden questions answered by calling the new Master Gardener Help Line at 218-824-1068 and leaving a message. A master gardener will return your call. Or, emailing me at and I will answer you in the column if space allows.
University of Minnesota Extension Master Gardeners are trained and certified volunteers for the University of Minnesota Extension. Information given in this column is based on university research.

A reader of Ask the Master Gardener sent this photo of a puffball mushroom. Contributed

A reader of Ask the Master Gardener sent this photo of a puffball mushroom. Contributed

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