Wait, see with ‘sick’ evergreen

We have a “sick” arborvitae on our property. It’s brown at the top and down on the south side. What’s going on and what can we do about it?

— Margaret

Actually, I’m seeing a bit of this problem on arborvitae as I’m driving around town. People love arborvitae as an alternative to junipers because besides smelling great they are soft and not prickly and itchy like junipers are. The downside to them is that they’re more sensitive to watering issues, especially drought.

What you’re seeing is most likely a combination of some winter drought damage and sunburn. Winter drought is a common issue with certain plants like Colorado spruce, birch, redbud and your arborvitae. Even though it’s cold and the soil is frozen, it can dry out due to our common lack of winter snow cover, low humidity and bright sunny days. The soil dries slowly, but it still dries and drought can hurt a plant in January just as much as it can in July.

I’ll usually recommend that people water these sensitive plants about once a month through the winter, tailoring that schedule in response to whatever the weather is doing. If temperatures are above average and there’s not much precipitation, then maybe those plants need to be watered two, three, or even four times a month. On the other hand, if there’s plenty of snow or rain, you can “suspend the clock” until it melts off and things start drying out again.

Most commonly, our driest part of the “winter” season is November. That wasn’t the case this past year — we had good amounts of precipitation November, December and January. However, February and March have both been dry and much warmer than average and I suspect that’s when most things have gotten hurt.

Sunburn is also wrapped up in this problem, because if a conifer evergreen is somewhat drought stressed, any damage usually shows up on the south or west side of the plant, since that’s the side most exposed to the sun and more prone to desiccation.

I wouldn’t do anything right now — it’s possible that the damage isn’t as bad as it appears now. Many arborvitae turn an amber yellow-brown tinge during the winter months. This is perfectly normal and that foliage will revert to green once things start warming up and the plant starts to grow. Wait until things start growing to see what’s alive and what’s not and then decide whether it’s worth hanging in with the plant and pruning out the dead or digging it up and starting over.

 

I have a poplar tree in my backyard that is a year and a half old. Over that time it’s done a few funny things. Upon planting it, the leaves went yellow in the summer; I think we were overwatering. Last summer (summer No. 2) we went easy on the watering and the tree grew very well with the exception of one strange thing — the new leaves that grew on the bottom branches were small to regular size (2 inches to 4 inches across), but the leaves that grew on the top part of the tree were extremely huge (10 or more inches across).

Over this winter the center top-most branch curled over, twisted a bit and shriveled up. Will the shriveled-up top branch straighten back up and grow as we move into spring or do I need to cut it off so that the top of the tree continues to grow straight?

— Kevin

 

Those big leaves you saw last summer are completely normal. In fact, they are a good sign. When members of the genus populus (cottonwoods, poplars, aspens) are planted, their leaves are relatively small and somewhat sparse. They do this while they’re putting most of their energy below ground, rooting out and establishing themselves.

Once that process has happened, they’ll often push out growth that has these oversized leaves like you saw. I like to term it “exuberance” on the part of the tree. People often think they got a cottonwood instead of a petite aspen or something. It’s just a sign that the tree is happy and progressing. This coming year I would expect your tree to “downshift” and produce more normal-sized leaves.

However, it’s still normal for a cottonwood to produce slightly larger leaves later in the season compared to the leaves that first came out in the spring.

Those curled-over stems are not going to straighten out for you. I’d get up on a ladder now and just cut the tips off.

Dennis Hill is the nursery manager at Bookcliff Gardens, 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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