How to Water Newly Planted Trees and Shrubs in a Minnesota Summer

The #1 reason new trees and shrubs die in Minnesota isn’t cold. It’s underwatering in the first summer. You plant a gorgeous ninebark in May, it looks good through June, then July hits and it’s uphill from there. By August, the edge leaves are crisp, and by September you’re wondering whether it’ll come back.

It generally comes back if you water right. Here’s the system we give every customer that buys trees and shrubs from Three Timbers.

How Minnesota summers kill new plantings

June is wet. July and August typically get 3–4 inches of rain total, and in drought years (like 2021, 2023), it’s much less. Heat hits 80s&cdash; 90s for days at a time. Windy afternoons wick moisture from leaves faster than roots can replace it.

A new tree’s roots are still confined to its 1-gallon or 5-gallon root-ball space - not the extended root zone of an established tree. That root ball can dry completely in 2-3 days during a Minnesota heat wave — even if the surrounding soil looks fine.

The first-year watering schedule

There’s a simple rule that gets you 95% of the way there: Water deeply, infrequently, at the root-ball — not a sprinkle.

Weeks 1-4

Deep soak 2/ times per week. New plants are still sending down initial roots.

Method for shrubs: leave a hose at trickle setting at the base for 10-15 minutes.

Method for trees: leave a hose at trickle setting for 20-30 minutes, or use a 5-gallon bucket with a pinhole in the bottom (a “tree drip bucket”) placed at the root-ball edge.

Weeks 5-8

Transition to 1 deep soak per week (unless there’s been a real rain event — 1+ inch, not a quick shower).

Weeks 9 to end of summer

Continue 1/per-week deep soak in hot, dry weather. When it rains heavily, skip.

If you have no rain for 1 week and temps above 85, do a 2/ time week — go back to week-1 frequency. New plants are still vulnerable the first summer.

Fall

Keep watering 1 time per week until the ground freezes (late November/early December). Fall watering is critical — evergreens and newly planted deciduous trees need moisture going into winter.

How to tell if you're watering enough

Two quick tests:

1. Soil probe (a long screwdriver works): push into the ground at the root-ball edge. It should push in 6-8 inches with moderate resistance. If it’s resistant past 2 inches, you’re dry. If you can push it in to 12 inches and it’s muddy, you’re overwatering.

2. Finger in the mulch: pull back the mulch and feel the soil about 2 inches down. If it’s dry and crumbly, water. If it’s cool and moist, you're fine.

Signs of underwatering: - Leaf edges crisp and brown (especially in afternoon sun) - New growth wilting — drooping and not recovering at night - Leaves prematurely yellowing and dropping

Signs of overwatering: - Leaves yellowing from the inside out (not edges first) - Mushy stems at ground level - Consistently soggy soil even 48+ hours after watering - Algae growth on mulch

Mulch matters

A 2-3 inch layer of shredded hardwood mulch is the single biggest thing you can do to help new plantings survive a Minnesota summer. Mulch reduces evaporation by about 70%, moderates soil temperature, and protects the root ball from the fast-cycling heat/cool damage.

Keep mulch 2 inches away from the trunk or stems — piled-up “volcano mulch” creates moist, fungal conditions that are actually harmful.

Special cases

Evergreens

New pyramidal arborvitae, columnar spruce, and pines need especially careful fall watering. They transpire through winter and can suffer “winter burn” if dry going into cold. Water weekly through October and November.

Columnar trees

Ttin, tall trees (French pillar trees), columnar oaks, and espalier fruit trees have proportionally small root balls relative to their branch structures. Water them more carefully for the first 2-3 years.

Clay soil

Clay holds water longer — you can water less often, but deeper. One deep soak per week that fills the clay basin works well for clay-soil yards.

Sandy soil

Sands drains fast, so water more often (2/ times per week deep throughout summer) but less volume per session.

In-ground vs container

Containers (like arborvitae in planters) dry quicker than in-ground plantings. Check containers daily in hot weather.

Automate it

If daily vigilance isn’t realistic, set up a drip irrigation line on a timer: - PVC or poly tubing run from an outdoor spigot - Drip emitters (1 per shrub, 3–4 per tree) - Battery-powered timer: run 2 times per week, 30-45 minutes each time in early morning

The whole setup can be assembled for under $100 at any big-box garden store and takes about an hour. It’s the difference between all your new plants surviving and flipping a coin in late August.

FAQ

Do I need to water every summer after year one? Year 2: water deeply during real drought events (2+ weeks no rain). Year 3+: only during prolonged drought. After that, roots reach deep enough that natural rain is enough.

What if it’s rained this week? If you got a real 1 inch or more with rain gauge, skip the deep soak that week. A quick afternoon shower (or unreliable weather-app report) doesn’t count.

Do different plants need different amounts? Yes, but this schedule works for most. Acid-loving plants (rhododendron, bluejay holly) need more consistent moisture. Drought-tolerant natives (sumac, Juniperus) need less after establishment.

Can I use a sprinkler? Not ideal. Sprinklers wet foliage (encouraging fungal disease) and evaporate quickly. Use drip or drip buckets instead.

Keep your new plantings alive

Browse our tree collection and shrub collection. Every plant we sell comes with this guide — refer back to it all summer.