Yellowing needles on mugo pines are normal

Our mugo pines are about 5 years old. When the snow melted away from them many of the needles were yellowing. What can we do this winter to help them?

— June

Yellowing needles on mugo pine can be caused by a number of things, but most of the time, it’s a normal thing the plant does over the winter.

Individual plants will vary a lot in how much they do or don’t yellow in the winter. This isn’t a cause for concern. The needles will green up once warmer weather starts and the plant starts growing for the year.

However, if this is much more than what’s usual for the plant, then there’s something else going on. The weather we had in January certainly could be the cause.

Mugo pine are super cold-hardy, so this isn’t about the cold per se, but it could be a needle burn caused by the sun reflecting off that persistent snow cover we had for five or six weeks. Needle burns such as this are usually on the south or west quadrants of the plant, though occasionally they will show up in other spots. And actually, that cold can sometimes contribute to these needle burns. As cold as it was and as deeply as the soil froze, it could have affected the plant’s ability to absorb and/or transport water.

There’s nothing to do about either of these problems. The damage has been done and the plant will deal with it and continue growing in the spring.

This is almost always just a burn of the foliage, the stems and buds are fine and will push out new growth in the spring. Provide the best care you can to the plant in supporting its efforts to heal.

Another thing I occasionally run into is needle yellowing or browning because of root death, which is caused by oxygen starvation.

Roots need to breathe like we do, and though they’re dormant during the winter, there’s still some metabolic activity going on that involves the roots respiring which requires oxygen. I’ve run into situations when there’s a lot of puddled water that has frozen into a solid sheet of ice on top of the soil under and around the plant. This drastically reduces the oxygen available to the roots and you can see damage appear on the plant.

Frozen soil isn’t the problem. It’s when there’s a solid sheet (and I mean solid!) of ice surrounding the plant.

Other than that, pine needle scale could be the culprit. These tiny little guys occur along the needles and suck the sap from the plant.

You could bring a sample in for us to look at. It’s easy to diagnose and we can show you what they look like.

We’ve had a big pine needle scale outbreak for the past five or six years, but it seemed to ease off a bit last year. I think this epidemic cycle is over for now.

I doubt pine needle scale is your problem, but we’d be glad to look for you.

Is the first week of February too early to prune fruit trees?

— Pat

You are better off waiting until mid- to late March, just before bud break.

The reason we wait for that time is that pruning is a growth stimulant. Pruning too early can occasionally cause the plant to break bud earlier than it otherwise would.

Waiting until March is closer to when the tree usually breaks bud, yet it’s still dormant and the branching and structure are easily visible.

The advantage you gain by waiting is so small, that doing it now really doesn’t matter all that much. If you have the opportunity and the gumption to get the job done now, go for it.

Otherwise, it is a bit safer to wait several weeks.

Dennis Hill is the nursery manager at Bookcliff Gardens, http://www.bookcliffgardens.com. Send questions to Bookcliff Gardens, 755 26 Road, Grand Junction 81506; or email .(JavaScript must be enabled to view this email address).


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