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Ask a Master Gardener: Lemon trees, ant invasions and sterilizing pruning tools

Ask a Master Gardener: Lemon trees, ant invasions and sterilizing pruning tools

February 11th, 2018 by James Quinn, Regional Horticulture Specialist, MU Extension in Life & Entertainment

Q: I had an ant invasion last spring when we had a rainy spell. In past years I controlled them with a Borax bait product. It didn't work this spring, nor did any sprays or dust I applied in their path. They are very small black ants and headed into the kitchen cabinets. What kind are they and should I do to stop them this year?

A: The ant description and their appearance following a rainy spell match the odorous house ant, the most common home-infesting ant species in Missouri. They generally nest outdoors and in rainy spells go looking for food in other places, like your house. They are attracted to sweets or sugars. The recommended way to control them is with sweet bait, which your Borax product likely was. They may have gotten wary of this product, so a good tactic would be to switch to another product that uses a different active ingredient. I found that Raid has such a product.

To get a jump-start, you might try putting the bait outside your house or garage, along the wall, near where they have come in before. Late March or April would be a good time. Then monitor those traps and increase the number if their activity flares up. Read the label carefully as it may have some good suggestions.

Q: I have wild blackberries that are growing along the bank of a pond and do very well. I'd like to replace them with some cultivated thornless blackberries this spring. How do I kill them off to plant others?

A: You will need to kill off the wild blackberries before you establish tame plants. There are many crown buds just under the soil, waiting for spring weather to emerge. Being confident all those wild ones are gone will take a full year. The best way is to use a brush killer in May and June and then keep that area mowed. Brush killers don't harm most grass. If wild cane shoots pop up through the summer, treat them with more brush killer or another systemic herbicide. You should be ready to plant new blackberries in the spring of 2019.

Q: Should I sterilize my garden shears, pruners and hand saws after using? Someone said I could be spreading diseases if I don't. It's something I haven't ever done and now I'm confused.

A: After using pruning tools it is a good idea to clean them well. Sterilizing them isn't needed unless you have plant diseases on plants that you are pruning. If you are concerned you have a disease, then it would be good to get it identified. When you know what disease it is, you will get recommendations on how to control its spread. Spreading of a disease is much more likely within the same plant (e.g. apples) than between different plants (e.g. apples and oaks). For most general pruning, spreading of disease isn't common. Good products to sterilize pruning equipment with are 10 percent household bleach solution or rubbing alcohol.

Q: My mom has had this lemon tree in a pot for 50-plus years. How long can she expect it to live? What kind of lemon tree is this?

A: What a wonderful container lemon tree! I wish everyone had such good luck. There are many lemon trees that can grow in containers. The most commonly seen now is Meyer lemon, but its fruit is smooth. Another cultivar mentioned is Ponderosa, which has bumpy fruit. While this doesn't guarantee yours is Ponderosa, it was interesting to find a web page testimonial discussing a Ponderosa tree of 53 years from

On the life expectance of a lemon tree, according to a non-extension, yet, good site for home gardening topics,, "Lemon trees can live almost as long in containers as in the ground. For long container life, repot the tree into a larger container everyone to one-and-a-half years. It is important to use fresh soil when planting in a new pot." They also mention that a typical lemon tree lives 50 years, but can exceed 100. The biggest limitation is usually disease. A container tree should have less disease pressure, especially as there aren't citrus diseases endemic to Missouri. With luck, this tree might become a family heirloom!