Transplanting Plum Trees

Southwest Yard & Garden

by Dr. Marisa Thompson & guest contributor Dr. Curtis Smith

TUNE IN NEXT WEEK FOR A FOLLOW-UP COLUMN WITH ADDITIONAL TRANSPLANTING SUGGESTIONS FROM CITY OF LAS CRUCES URBAN FORESTER JIMMY ZABRISKIE!

‘Stanley’ plums at the NMSU Agricultural Science Center at Los Lunas in September 20, 2018. Photo credits M. Thompson.

Question: I had an individual call with questions about plum trees she needs to transplant. When is the best time to transplant? And what is the best method?

                                                -Cheyenne Law, Guadalupe County Extension Agent

Answer: This is a great question. The short answer is “when the trees are fully dormant,” so any time before they flower or leaf out in the spring. But I’d like to know more before giving a full answer. It really depends on how old and how big the trees are. I’d also like to know why these trees are being transplanted, where they’re going (what’s the soil type), and if they currently have any signs of stress (specifically borers).

After contacting the trees’ owner, Ms. Law reported back that these trees are 8 years old, about 7 feet tall, healthy and excellent producers in recent years, and being moved to a spot nearby because a garage is being built in their current location.

Plums are in that group of “short-lived trees,” along with peaches, apricots, cherries, and other Prunus species. Eight years isn’t too old for a plum, but it’s getting there. Some suggest 20 years to be a normal lifespan for a Prunus tree in New Mexico. I’ve heard as short as seven. So I was concerned that if these plum trees were older and/or already infested with borers, which are very common in our area, they might not be worth the expense and effort of transplanting. For more information, visit https://nmsudesertblooms.blogspot.com/ and search for the term “borers.”

I reached out to Dr. Curtis Smith, retired NMSU Extension Horticulture Specialist, for his input. Dr. Smith agreed that tree age and size are important when considering the pros and cons of transplanting trees, and that at 7 feet tall they might still be small enough for successful transplanting. He noted that as long as the soil isn’t frozen and can be dug, late January into February is probably the best time. “If the trees have been attacked by peach tree borers, transplanting success will be greatly reduced!”

Dr. Smith continued, “If the soil is obviously different (moving from sandy to clay or vice versa), this may create problems with irrigation and root establishment. Make the prepared planting hole considerably wider than the rootball.

Farmers and contractors often have access to equipment to allow taking a large rootball (2 to 2.5 feet deep for these trees, if possible, and as wide as possible). If access to a tree spade is possible (city parks, state parks, etc.), this would also make taking a large rootball possible and greatly increase the chances of success. If soil falls away, just plant and replace with moist soil quickly.

Keep the soil moist at the new planting site, but not overly wet. As the tree roots establish they will more rapidly remove water from the soil, so check the soil periodically to determine when to irrigate. If any trees fail to establish, this prepared site will be ready for new trees to be planted next autumn.”

Even if they go through with transplanting and even if the trees survive, I recommend planting a few new plum trees along with the transplants to stagger the tree ages with the expectation that the older trees might fail in the coming years.

Here are a few pointers from Dr. Smith and me to increase your chances of successful transplants:

·       Keep roots moist during the transplant procedure, and be sure the soil at the new planting site is also moist (maybe water the pre-dug hole the day before so it’s not soggy). Water thoroughly after planting. For more tips on tree irrigation, visit https://nmsudesertblooms.blogspot.com and search “water.”

·       Mulch new transplants on the soil surface with at least 4 inches of woodchips, woody fiber, bark mulch, or pine needles. Avoid pilling the mulch up against the trunk. So-called volcano mulching is a big no-no, so leave a few inches of “breathing room” at the base of the trunk.

·       Be sure not to plant too deep. The planting depth should be the same or even slightly higher after transplanting. Sometimes if the hole is dug too deep the tree can sink (even if it’s backfilled to the correct depth, sinking is common). The line where the tree trunk meets the soil should still be visible aboveground in the new spot. One rule of thumb when planting any tree is that the topmost root should be barely visible at the soil surface before mulch is applied. For more tips on tree planting, visit https://nmsudesertblooms.blogspot.com and search “the hole story.”

***Check out Dr. Curtis Smith's blog "Southwest GardenSmith" at https://www.southwestgardensmith.com/

For more gardening information, including decades of archived Southwest Yard & Garden columns, visit the NMSU Extension Horticulture page (http://desertblooms.nmsu.edu/), follow us on social media (@NMDesertBlooms), or contact your County Extension office (https://aces.nmsu.edu/county).

Marisa Thompson, PhD, is the Extension Horticulture Specialist for New Mexico State University and is based at the Agricultural Science Center at Los Lunas.