by Ken Lain, the mountain gardener
When is the best time to plant trees in the mountains? This question, pertaining to areas that experience cold winters, has both a long and a short answer.
When to Plant Trees: The Short Answer
In general, the best time for planting trees is late winter to early spring (February thru May).
This period typically is followed by a period of moderate weather, a good time for a new transplant to become established. If your schedule does not allow for a spring planting, then aim for autumn. Trees can be planted in summer in the mountains of Arizona, but closer attention to irrigation is essential.
When to Plant Trees: The Long Answer
For the long answer of when to plant trees, remember what has been said above, then add some elaboration. At this point, let’s introduce some garden vocabulary:
Dormancy is defined as the time from when a tree has dropped its leaves in fall and before new leaves appear in spring. Planting trees when they are dormant (when they are not operating at their peak growth rate) is best. When trees are dormant they are less disrupted by harsh handling and transplant shock. Yes, our mountain climate is mild enough that trees can be planted in mid-summer, but with greater care.
Deciduous trees are those that lose their leaves in autumn. The dropping leaves signal that those trees are entering dormancy; their unfurling of buds in spring signals they are leaving dormancy.
Evergreens do not undergo the kind of dormancy that deciduous plants do. As they do not send out the clear seasonal signs of dormancy, when to plant them is not easy to determine. Fortunately, evergreens tend to be truly tough trees, allowing more leeway in their planting times. Planting is ideal from fall through late spring. With many juniper, cypress, and cedar varieties planting continue well into the heat of summer. Again, summer heat mandates that newly planted evergreens be watered twice per week.
Now that you know when to plant trees, what about the how?
Trees, especially native pines, have trouble with our crummy mountain soil. They don’t like to sit in wet soggy soils. In a wet environment trees’ internal metabolisms are slowed to an almost stasis-like state. New root hairs will form along with next spring’s buds as long as the soil drains properly. That’s why digging the right size planting hole and adding the correct soil amendments are critical towards a successful planting.
Here are the six steps to planting a tree successfully, no matter the season.
Step 1 – The bowl-shaped hole should be the same depth as the root ball, and three times as wide. Plants do not need a deep hole; they thrive when able to stretch out just under the surface of the soil in search of food and water. This is why a bowl-shaped hole promotes the best root development. Rid the hole of rocks and debris larger than a golf ball.
Step 2 – Improve the planting soil by amending with ‘Watters Premium Mulch‘. Good mulch will keep clay soils loose and aerated, and in loose granite will retain water up around the root ball. The amount of mulch per plant should be equal to the size of the root ball. That is the quantity of mulch you will need to blend into the native soil used to fill in around each plant.
Step 3 – Trees are so sensitive to soggy soil it’s recommended they be planted on a slight mound. Do NOT bury the plant; keep the trunk out of the soil. The top of the root ball visible in the grower’s pot should still be able to see sunlight once planted.
Step 4 – Trees need the right plant food for a healthy start. Use my specially blended “All-Purpose Plant Food” 7-4-4, specifically designed for Arizona’s mountain plants. Just sprinkle the granules on top of the root ball and water in well. The slow-release nutrients promote a plant’s deep green color while encouraging thicker root formation each time it is watered.
Step 5 – Promote deep roots for a new planting by using Watters ‘Root & Grow’. Add this liquid rooting hormone to the water you use to saturate the newly planted root ball. It forces many new root hairs to grow into the surrounding soil. More roots mean a more vigorous plant. Use this root tonic once per month until new leaves or evergreen candles emerge in spring.
Step 6 – Top dress the planting area with a 3-inch layer of shredded cedar bark. This extra layer of nature’s insulation retains moisture, keeps out weeds, and protects from extreme temperature swings. It is like pulling a thick wool blanket over the roots when they are cold and shivering.
Water – Give newly planted trees a thorough soak twice per week throughout the growing season. Keep established trees moist, but allow them to dry between waterings.
For exact planting details that include drawings and measurements, ask for my “Guide to Mile High Planting” the next time you visit the garden center. You might also like the useful companion guide “Mile High Watering”.
Until next week, I’ll be here at Watters Garden Center helping local gardeners plant the perfect trees.