When To Fertilize Arborvitae

Knowing when to fertilize arborvitae is one of the most important things you can do for their health. Getting the timing right ensures these popular evergreens stay dense, green, and resilient all year long.

This guide walks you through the essential seasonal schedule. We’ll cover the best times to feed your plants, what type of fertilizer to use, and how to apply it correctly for fantastic results.

Arborvitae are not heavy feeders, but they do benefit from the right nutrition at the right time. The goal is to support steady, healthy growth without encouraging a burst of tender new shoots that could be damaged by cold.

Best Time of Year for Feeding

The ideal feeding window is in the early spring. Aim to fertilize just as the ground thaws and before new growth begins, usually around late March to mid-April, depending on your climate.

This gives the tree nutrients exactly when it’s waking up and ready to grow. A second, lighter application can be done in the early fall, around September, to help the roots store energy for winter.

Primary Feeding: Early spring (pre-growth).
Optional Secondary Feeding: Early fall (for root strength).
Never Fertilize: Late fall or winter, as it can promote vulnerable new growth.

Signs Your Arborvitae Needs Fertilizer

Healthy arborvitae should have a consistent, rich green color and produce several inches of new growth each year. Watch for these signs that indicate a need for nutrients:

Yellowing or browning needles, especially on older inner growth.
Stunted or sparse new growth each season.
Overall pale or faded green color compared to healthy plants.
Needles that appear thin or weak.

Remember, these symptoms can also be caused by other issues like drought, pests, or poor planting. Always check soil moisture and rule out other problems first before deciding to fertilize.

Choosing the Right Fertilizer

Selecting the correct product is just as crucial as timing. A balanced, slow-release fertilizer is generally the best choice for arborvitae.

Understanding NPK Ratios

Look for a fertilizer bag with three numbers, like 10-8-6 or 14-7-7. This is the NPK ratio, representing Nitrogen (N), Phosphorus (P), and Potassium (K).

Nitrogen (N): Promotes healthy green foliage and stem growth. This is the most important number for arborvitae.
Phosphorus (P): Supports strong root development.
Potassium (K): Aids in overall plant vigor and disease resistance.

A balanced ratio, where the first number (N) is slightly higher, works very well. Espcially for newly planted trees, a fertilizer with a good phosphorus content can help establish roots.

Slow-Release vs. Quick-Release Formulas

Slow-release fertilizers are prefered. They feed the tree gradually over several months, providing a steady supply of nutrients and reducing the risk of burning the roots.

Quick-release fertilizers give a sudden, intense nutrient surge. They can sometimes cause rapid, weak growth and require more careful application to avoid damage.

How to Apply Fertilizer: A Step-by-Step Guide

Proper application ensures the tree’s roots can access the nutrients efficiently and safely. Follow these steps for the best outcome.

Step 1: Calculate the Right Amount

More is not better. Over-fertilizing can burn roots and harm the tree. Always follow the label instructions on your chosen product. A general rule is to use about 1 pound of nitrogen per 1,000 square feet of root zone area per year.

For a simple guideline, you can use 1 cup of a balanced granular fertilizer for every foot of the tree’s height. So, a 5-foot arborvitae gets about 5 cups. Distribute this evenly under the canopy.

Step 2: Apply Evenly to the Drip Line

The feeder roots of an arborvitae extend out to the “drip line”—the area directly under the outermost branches. This is where you should concentrate the fertilizer, not right against the trunk.

Measure the correct amount of fertilizer.
Starting a foot away from the trunk, sprinkle the granules evenly on the soil surface under the entire canopy.
Try to reach just beyond the drip line for best coverage.

Step 3: Water Thoroughly

This step is essential. After applying the fertilizer, water the area deeply. This helps dissolve the granules and carries the nutrients down to the root zone.

It also prevents the fertilizer from sitting on the surface, which could potentially burn the foliage or the roots. A good, slow watering for about 30 minutes is usually sufficient.

Special Considerations for New and Established Trees

Your fertilization strategy should change slightly based on the age and condition of your arborvitae.

Newly Planted Arborvitae

Hold off on fertilizing right at planting time. The tender new roots can be easily damaged. Instead, wait until the tree has been in the ground for at least 6-8 weeks, or even until its second growing season.

When you do first fertilize, use a half-strength dose of a balanced, slow-release product to gently encourage establishment without stress.

Mature or Hedge Arborvitae

Large, established trees often need less frequent feeding. If they are growing well and are a healthy color, you might only need to fertilize every other year or even every three years.

For dense hedges, which are growing more closely together and competing for soil nutrients, a consistent annual spring feeding is usually beneficial to maintain their vitality and color.

Seasonal Care Calendar for Arborvitae

Fertilizing is just one part of annual care. Here’s a quick seasonal overview to keep your trees in top shape.

Early Spring: Apply slow-release fertilizer. Prune for shape if needed.
Late Spring/Early Summer: Monitor for pests like bagworms. Water during dry spells.
Mid-Summer: Continue deep watering during periods of drought. Avoid pruning in hot weather.
Early Fall: Optional light fertilizer application. Plant new arborvitae.
Late Fall: Water deeply before the ground freezes for winter hydration.
Winter: Protect young trees from heavy snow load that can bend branches.

Common Fertilizing Mistakes to Avoid

Even with good intentions, it’s easy to make errors. Steer clear of these common pitfalls.

Fertilizing at the Wrong Time: Late summer or fall feeding can trigger new growth that won’t harden off before frost.
Over-Fertilizing: This leads to salt buildup in the soil, which burns roots and causes needle browning.
Placing Fertilizer at the Trunk: The active roots aren’t there, so the nutrients go to waste and can even rot the trunk base.
Ignoring Soil pH: Arborvitae prefer slightly acidic soil. If your soil is too alkaline, nutrients get locked up. A soil test can tell you if you need to adjust the pH.
Forgetting to Water it In: Unwatered fertilizer is ineffective and potentially harmful.

FAQ: Feeding Your Arborvitae

Can I use lawn fertilizer on my arborvitae?

It’s not recommended. Lawn fertilizers are often high in nitrogen and quick-release, which can cause excessive, weak growth on trees and potentially damage them. It’s best to use a product formulated for trees and shrubs.

Is Miracle-Gro good for arborvitae?

Miracle-Gro offers tree and shrub plant food that can be suitable. Look for their slow-release shrub fertilizer spikes or granular formulas with an appropriate NPK ratio. Always follow the label directions for evergreens.

How often should you fertilize arborvitae?

For most established, healthy arborvitae, an annual feeding in early spring is perfect. Younger trees might benefit from a second light feeding in early fall, while very mature, thriving trees may only need feeding every two to three years.

What is the best fertilizer for emerald green arborvitae?

Emerald Green arborvitae, like other varieties, do well with a balanced, slow-release granular fertilizer. A ratio like 10-10-10 or 14-7-7 applied in early spring will support its vibrant green color and dense growth habit.

Can you fertilize arborvitae in the summer?

It’s generally not advised. Fertilizing in the heat of summer can stress the tree, especially if conditions are dry. The ideal times remain early spring and, if needed, early fall when temperatures are milder.

By following this seasonal guide, you provide your arborvitae with the foundation they need. The key is consistency: the right food, at the right time, applied in the right way. With this simple care routine, your trees will reward you with lush, durable beauty for many seasons to come.