Your Tree Questions, Answered by Erik Renstrom of Renstrom Tree Service (White Bear Lake, MN)
Trees are a big part of Minnesota life, from shade in the summer to protection against winter winds. In this new 3-part series, we’re sitting down with local arborist Erik Renstrom of Renstrom Tree Service to answer some of the most common questions we hear from homeowners in the White Bear Lake area.
Erik, when’s the best time to trim my trees in Minnesota?
Erik: For most trees here in White Bear Lake, the dormant season—late fall through early spring—is the best time to prune. With the tree resting and no leaves in the way, we can see the structure more clearly, and the cuts heal more efficiently. For oaks specifically, trimming should only happen in late fall or winter to avoid oak wilt, which is a real concern in our area.
My oak tree looks healthy—do I really need to worry about oak wilt around White Bear Lake?
Erik: Absolutely. Oak wilt is a fast-spreading disease in Minnesota, and I’ve seen entire sections of neighborhood oaks wiped out. Once it gets into your tree, it’s often too late. Preventative pruning during the safe months and avoiding wounds to your oak in spring and summer are the best defenses.
Do storms in Minnesota cause more long-term damage than people realize?
Erik: Yes. After a big storm, most people look for broken branches, but damage isn’t always obvious. Cracks in the trunk, roots pulled up, or branches weakened by heavy snow can create future hazards. That’s why we always recommend a post-storm inspection, especially in areas like White Bear Lake where strong winds and heavy snowfall are common.
What’s one mistake homeowners around here make with their trees?
Erik: Over-mulching. I see this all the time—what we call “mulch volcanoes” around tree trunks. In Minnesota’s wet springs, piling mulch too high can rot the bark and invite pests. Mulch should be spread like a donut, not a volcano, and kept a few inches away from the trunk.
Are ash trees in White Bear Lake still at risk from emerald ash borer?
Erik: Unfortunately, yes. The emerald ash borer has been devastating Minnesota ash trees for years. If you have a healthy ash tree you want to keep, proactive treatment is still the best option. Otherwise, it’s often smarter to plan for removal before the infestation makes the tree unstable.
Is there a way to prepare trees for Minnesota winters?
Erik: Definitely. Young trees and sensitive species benefit from tree wraps to prevent sunscald and frost cracks. Also, proper watering before the ground freezes is key—many people forget that even in fall, trees need water to go into winter healthy.
Should I fertilize my trees in the White Bear Lake area?
Erik: Our soils here can be heavy and sometimes nutrient-poor. A slow-release fertilizer applied in the fall or early spring can give your trees the boost they need. That said, I always suggest soil testing before applying anything—it ensures you’re giving the tree what it actually needs.
I’ve got a large maple tree close to my house. Should I be worried about its roots damaging my foundation?
Erik: It depends on the distance and the soil type. In most cases, the roots of maples and other large trees aren’t strong enough to crack modern concrete foundations, but they can invade sewer lines if there are cracks or openings. A root inspection can give you peace of mind.
What’s the benefit of hiring a local company like Renstrom Tree Service compared to a bigger outfit from the Twin Cities?
Erik: We know White Bear Lake’s trees and weather patterns firsthand because we live here. Big companies might send out crews who don’t understand local issues like oak wilt timing or heavy snow load damage. With us, you get expertise tailored to our community—and we show up when you need us most.
What’s your number one piece of advice for tree care in Minnesota?
Erik: Don’t wait until it’s an emergency. Whether it’s pruning, disease prevention, or storm prep, proactive care saves money and keeps your property safer. Trees are an investment—and in White Bear Lake, they’re also part of what makes living here so beautiful.
Stay tuned for Part 2 of Ask the Arborist, where we’ll dive deeper into topics like emergency tree removal, specialty equipment (like our tracked aerial lift), and tips for protecting your trees during summer storms.
Erik Renstrom
For over a decade, Erik Renstrom, along with his company Renstrom Tree Service have been servicing the Minneapols / St. Paul area, helping home owners and businesses with their trees. Whether you have a tree that has fallen on your house or need storm damage cleanup, we are here for you, 24-7. Call Erik today! (651) 363-9616