West Polk Soil & Water Conservation District - Care for newly planted trees critical

Submitted by Morgan Torkelson
Crookston Times

During this unseasonably hot and dry spring, West Polk SWCD wants to remind area readers to care for newly planted trees during their critical first year. The process of transplanting a bare root or container-grown tree is very taxing on them and puts them at the mercy of Mother Nature. Their root systems have either been reduced severely (bare root trees) or confined to a very small volume of soil (container-grown trees). Until these plants grow new roots that venture outward for resources, they will require regular watering. This is especially important for container-grown trees. Until a tree has a sufficient root system, all of its water demands must be met by the few roots inside its transplanted root ball. Not only can this small root ball be depleted quickly in hot weather but without timely watering in fall, winter burn can be a concern too.

Deep watering is best. Until soaking rainfalls (anyone remember those?) convince young tree roots to explore far and wide, your focus should be on sending water downward where it will be less likely to evaporate or be taken up by nearby weeds or turf. Building a small soil berm around a tree will force water downward into your tree’s root zone instead of letting it run off. When you water, fill this reservoir to the top, let it soak in and then fill it again. “Double watering” is a great way to get water down where it will benefit your tree the most.

Know your soil and planting site and water accordingly. Check the soil around some of your trees every time you water. If it always seems to be dry a few inches deep, you might need to water more often. If it is staying wet near the surface, you might need to water less often. Too little water can quickly kill young trees, but too much can drown them (especially in clay soil). If we're getting less than 1" of rain per week, watering once a week in sandy soil and every 1-2 weeks in clay is a good place to start. Hot weather, dry air, weed competition, sun and wind exposure as well as tree size can all increase water demand so keep that in mind.

Control competition. If you don’t take steps to control turf and weeds, a lot of your watering effort will be spent giving nearby vegetation a leg up on your trees. The best way to do this is to apply a 4” deep, ~3’ wide layer of wood chip mulch around the tree. Remove vegetation or mow it short in this area and then spread the mulch so that it doesn’t touch your tree’s stem. That’s it! Mulch will retain moisture, snuff out competition and improve the quality of your tree’s soil. It will also insulate the soil – keeping roots cool on hot, sunny days and mitigating damaging freeze/thaw cycles in the cold months. If you can’t get wood chips, a weed mat or a thin layer of rotted leaves or dry cut grass can provide similar benefits.

For larger plantings, shallow tillage near young trees can also be a quick way to knock back freeloading weeds, but it has drawbacks. Although tilling is effective at disrupting weeds, it will destroy shallow tree roots too. It also makes soil susceptible to compaction, drying, erosion, salt accumulation and damaging temperature extremes. For these reasons, tillage is not recommended as a long-term strategy. Instead, consider planting a mix of low-maintenance native prairie grasses and forbs once your trees are established. Native bunchgrasses won’t compete for resources like sod grasses will. Just mow them once or twice a year to control weeds and they will help keep your trees’ roots thriving.

If you have any questions or want to talk about other ways to make growing trees as easy and rewarding as possible, email me at morgan.torkelson@wpolk.mnswcd.org or call West Polk Soil & Water Conservation District at (218) 281-6070 for more information.