Most evergreens want acidic soil at pH 5.0 to 5.5, or slightly acidic soil at pH 6.0 to 6.5. Penn State Extension gives both bands, because evergreen soil pH is not one number that covers one plant. Anything inside those two bands is workable ground. Anything well outside them turns into a project you did not sign up for.
A soil test settles the evergreen soil pH question before you buy the tree or dig the hole, and that order is the whole trick. The reading tells you which evergreens belong on your list and which ones stay at the nursery. Test first. Once a root ball is in the ground, you are working around a plant instead of ahead of one, and every fix from that point on is harder than it needed to be.
The group splits inside that range. Rhododendron leans toward the more acidic end and does best down near 5.0. Japanese yew, spruce and fir ask for ground that is barely acidic, so the upper numbers suit them fine. The gap between 5.0 and 6.5 looks small written down, and it hands you two different shopping lists. Acidic soil for conifers is a fair opening assumption, and you still pin the target to the plant you picked rather than to the word evergreen printed on the tag.
Push above that band and iron becomes the thing to watch. Iron deficiency is common in high-pH soils, and it runs more serious in some evergreen species than in others. So the iron chlorosis evergreens run into on high-pH ground depends on what went in the hole. Two trees can share the same bed and only one of them shows it. Species choice carries as much weight here as the number on the test.
Drainage sits right beside pH, and it fools people. Wet or poorly drained soil is a documented cause of abnormal needle drop, so a tree can sit at a perfect reading and still shed needles on you. Walk the spot after a heavy rain and watch how long water stands there. If it lingers, pH is not your first problem.
Two of the most common evergreen complaints start in the ground rather than in the tree. Needle drop on soil that stays wet is one of them, and an evergreen sitting in high-pH ground is the other. Both are worth ruling out before you go hunting for a pest or a disease. And they cost far less to settle before the tree goes in the ground than after it has spent a full season in the wrong spot.
Never add sand alone to a clay soil. Test the ground first, correct the pH and the drainage second, and plant third.
If your test comes back above the more acidic band and you had your heart set on a rhododendron, plant something else. A yew or a spruce asks less of that same ground and settles in on its own. Matching the plant to the soil beats correcting the soil for the plant. The evergreen soil pH you already have costs nothing to work with, and changing your mind at the nursery is free.
Depth is the last piece of it. Most of the roots that take up water and nutrients sit in the top 6 to 18 inches (15 to 46 cm) of soil. That shallow band is the part you can reach and change before planting day, and it is the part the tree lives off once it is in. Get it right up front. Then the first season goes to growth instead of repair.
Read the full article: Evergreen Trees: 8 Types and How to Choose
