If you’re a Colorado gardener, you know timing is everything. Knowing when is the best time to plant trees in Colorado is the single most important step for their long-term survival. Our state’s unique climate, with its intense sun, drying winds, and dramatic temperature swings, demands a smart planting schedule. Get it right, and your tree will establish strong roots and thrive for decades. This guide will walk you through the optimal seasons and give you clear, step-by-step instructions for success.
When Is The Best Time To Plant Trees In Colorado
For most of Colorado, the absolute best time to plant trees is during the dormant seasons: fall and early spring. The ideal windows are typically from mid-September to mid-October in the fall, and from late March to mid-May in the spring. These periods avoid the summer’s heat stress and the winter’s frozen ground, giving roots the perfect conditions to grow.
Why Fall Planting is Often #1
Many expert arborists favor autumn planting for Colorado’s climate. The air is cool but the soil is still warm from the summer sun. This combination encourages root growth without the demand for supporting top growth or leaves. The tree can focus its energy entirely underground.
- Less Water Stress: Cooler temperatures mean less evaporation. Your new tree will lose less water through its leaves (if it has any) and requires less frequent watering.
- Head Start on Spring: A fall-planted tree establishes roots all autumn and, during mild winter spells, will begin growing roots again early in spring. It’s ready to explode with growth when the warm weather arrives.
- More Rainfall: Fall often brings more consistent moisture to many parts of the state, providing natural assistance.
The key is to plant at least 4-6 weeks before the ground freezes hard. This gives the roots enough time to start anchoring themselves.
The Case for Spring Planting
Spring is a very close second and is excellent for many tree species, especially those more sensitive to cold. The window begins as soon as the ground is workable—not muddy, but thawed.
- Full Growing Season Ahead: The tree has the entire spring and summer to establish itself before its first winter.
- Ideal for Tender Species: Broadleaf evergreens or trees that are marginally hardy in your zone benefit from the full season to toughen up.
- Easier Monitoring: You’re already active in the garden, so it’s simpler to keep an eye on watering needs.
The main challenge is Colorado’s unpredictable spring weather. Late frosts, heavy spring snows, and rapid shifts to hot, dry, windy days can stress a new planting. Consistent watering is absolutely critical through the first summer.
Seasons to Avoid
Summer and deep winter are the worst times to plant in Colorado. Summer planting forces a tree to cope with extreme heat, intense sun, and dry air while trying to heal damaged roots. It requires heroic and constant watering. Winter planting is simply impossible when the ground is frozen solid. You cannot properly prepare the planting hole or ensure good root-to-soil contact.
Choosing the Right Tree for Your Zone
Colorado spans USDA Hardiness Zones 3 through 7. Picking a tree rated for your specific zone is non-negotiable. A tree suited for Zone 5 will likely perish in Zone 3. Always check the tag.
- High Plains & Front Range (Zones 4-5): Focus on drought-tolerant, wind-resistant natives. Excellent choices include Bur Oak, Hackberry, Kentucky Coffeetree, Pinyon Pine, and various maples like the Bigtooth.
- Mountain Regions (Zones 2-4): Cold-hardiness is paramount. Look to Subalpine Fir, Engelmann Spruce, Quaking Aspen, and Limber Pine.
- Western Slope & Warmer Valleys (Zones 5-7): You have more options, like some species of Oak, Linden, and even some carefully sited fruit trees.
Don’t forget microclimates! A sheltered south-facing wall creates a warmer spot than an exposed north-facing slope.
Your Step-by-Step Planting Guide
Proper planting technique is as important as timing. Follow these steps to give your tree the best foundation.
1. Prepare the Planting Hole
The old advice of digging a deep hole is wrong. You want a wide, shallow hole. Dig it 2-3 times wider than the root ball, but only as deep as the root ball itself. The root flare (where the trunk widens at the base) must sit slightly above the surrounding grade. Colorado’s heavy clay soils can act like a bathtub, drowning roots if the tree is planted too deep.
2. Handle the Root Ball
For container-grown trees, gently loosen and spread any circling roots. For balled-and-burlapped trees, carefully remove any wire basket and synthetic burlap after placing it in the hole. Natural burlap can be left in place but pulled back from the trunk.
3. Backfill with Native Soil
Do not amend the backfill soil with compost or potting mix. You want the roots to adapt to the native soil immediately. Amending just creates a comfortable “pot” that roots may never leave. Use the soil you dug out, breaking up large clods.
4. Water and Mulch Deeply
As you backfill, water periodically to settle the soil and remove air pockets. Then, create a wide, shallow mulch ring. Apply 3-4 inches of wood chips or shredded bark, but keep the mulch a few inches away from the trunk itself. This conserves moisture and insulates roots.
5. Establish a Watering Schedule
This is the most critical aftercare step. Your tree will need consistent moisture for the first 2-3 years, not just the first few weeks.
- Year 1: Water deeply 2-3 times per week, depending on weather. The goal is slow, deep soaking.
- Year 2: Water deeply once a week, tapering off in the fall.
- Year 3: Water every other week during dry periods.
Always check soil moisture a few inches down before watering. A soaker hose or drip irrigation is far better than a quick spray with a sprinkler.
Common Mistakes to Sidestep
- Planting Too Deep: This is the #1 cause of tree failure. Always locate the root flare.
- Over-amending the Soil: Resist the urge to create a rich planting mix. It does more harm then good.
- Staking Unnecessarily: Most trees don’t need staking. If you must stake for wind support, use wide, flexible ties and remove them after one year.
- Underwatering: Colorado’s dry air pulls moisture from leaves rapidly. Deep, infrequent watering is key.
- Using “Weed & Feed” Nearby: Herbicides can damage or kill young trees. Be very careful with lawn chemicals.
FAQs: Planting Trees in Colorado
Can I plant trees in Colorado in the summer if I water a lot?
It’s highly not recommended. Even with frequent watering, the heat stress on a trying-to-establish tree is immense. Survival rates drop significantly. Wait for fall.
What is the best month to plant trees in Colorado?
For fall, aim for September. For spring, April is generally safe for most areas, but watch the soil condition not just the calendar.
How late in fall can you plant trees in Colorado?
You can plant up until the ground freezes, but for best results, finish by mid-October. This gives roots those crucial weeks to settle in.
Is it better to plant in spring or fall in Colorado?
Both are excellent. Fall has slight advantages, but spring works wonderfully too, especially if you are diligent with summer watering.
What are the most important factors for tree survival here?
The trifecta is: 1) Correct tree for your zone, 2) Proper planting depth, and 3) Consistent, deep watering during establishment. Miss any of these, and the tree will struggle.
By following this seasonal guide and planting steps, you’ll give your new tree the strongest possible start. Your careful timing and technique will be rewarded with a healthy, beautiful tree that grows strong for generations to enjoy. Remember, the right time makes all the difference in our challenging and rewarding Colorado climate.