Arborvitae benefit most from fertilizer applied in early spring before new growth begins, with a second light feeding in late summer. Knowing when to fertilize arborvitae is the difference between a lush, vibrant screen and a sparse, yellowing hedge. Many homeowners guess at the timing, but a simple schedule aligned with the plant’s natural growth cycle delivers the best results.
You don’t need a degree in horticulture to get this right. The process is straightforward, and the rewards are visible within weeks. Let’s break down the perfect feeding calendar, the right products to use, and the common mistakes that can harm your trees.
When To Fertilize Arborvitae
The single most important rule is to feed your arborvitae just as the soil begins to warm up in early spring. This is when the roots are waking up and are most receptive to nutrients. A second, lighter application in late summer helps the tree store energy for the winter months ahead.
Avoid fertilizing in the heat of midsummer or during the fall. Late-season feeding pushes out tender new growth that won’t harden off before frost. That soft growth is easily damaged, leaving your arborvitae with brown tips and winter burn.
Why Early Spring Is The Golden Window
In early spring, the ground is thawing, and the tree’s root system is actively expanding. The soil temperature is just right for nutrient uptake. Fertilizer applied now gives the tree a direct boost for the coming growing season.
- Roots absorb nutrients efficiently in cool, moist soil.
- New growth in spring is strong and resistant to pests.
- Early feeding reduces the risk of burning the roots.
- It supports the development of dense, rich green foliage.
The Late Summer Follow-Up Feeding
Your second application should occur about six to eight weeks before the first expected frost. This is usually in late August or early September. This feeding is not about pushing growth; it’s about building root strength and carbohydrate reserves.
Use half the amount you used in the spring for this application. The goal is to sustain the tree, not to stimulate new shoots. This timing also helps the arborvitae maintain its color through the fall and into the winter.
Signs Your Arborvitae Needs Fertilizer
Not every arborvitae needs fertilizer every year. In fact, over-fertilizing is a common problem. Look for these visual cues before you mix any solution.
Visual Symptoms Of Nutrient Deficiency
If your arborvitae is lacking nutrients, it will tell you. The foliage will change color and texture. You might notice a general lack of vigor even when the tree is watered properly.
- Foliage turns a pale green or yellowish color instead of deep green.
- New growth is stunted or sparse compared to previous years.
- The lower branches lose leaves and become bare.
- The tree seems to grow slower than it did in the past.
If you see these signs, a spring feeding is likely necessary. However, if the tree looks healthy and grows well, you can skip the fertilizer entirely. Sometimes, the best thing you can do is nothing at all.
Choosing The Right Fertilizer For Arborvitae
Arborvitae are not heavy feeders, but they do have specific needs. They prefer a fertilizer with a higher nitrogen content to promote green foliage. Look for a slow-release formula to avoid burning the shallow roots.
Slow-Release Granular Fertilizer
This is the most common and safest option for arborvitae. The granules break down slowly over several months, providing a steady supply of nutrients. You apply them to the soil surface and water them in.
Look for a balanced formula like 10-8-6 or 12-6-4. The first number (nitrogen) should be the highest. This supports leaf and stem growth, which is exactly what you want for a privacy screen.
Liquid Fertilizer Options
Liquid fertilizers are fast-acting and good for a quick pick-me-up. They are absorbed through the leaves and roots almost immediately. However, they don’t last as long as granular types and require more frequent applications.
Use a liquid fertilizer only if you see a sudden deficiency or if you are correcting a specific problem. For routine feeding, stick with granular slow-release products. They are more forgiving and easier to manage.
Organic Alternatives
Compost and well-rotted manure are excellent organic options. They improve soil structure and provide a gentle release of nutrients. You can top-dress the soil around the base of the tree in early spring.
Organic fertilizers are less concentrated, so there is almost no risk of burning the roots. They are a great choice for gardeners who prefer a natural approach. Just be aware that they take longer to show visible results.
How To Apply Fertilizer Correctly
Applying fertilizer is not just about throwing granules on the ground. The root zone of an arborvitae extends well beyond the drip line of the branches. You need to target the entire root area for the best absorption.
Step-By-Step Application Guide
- Measure the diameter of the trunk at chest height. This helps you calculate the amount of fertilizer needed.
- Scatter the granules evenly over the soil surface, starting about six inches from the trunk and extending out to the drip line.
- Water the area thoroughly after applying. This helps the granules dissolve and reach the roots.
- Do not pile fertilizer against the trunk. This can cause rot and attract pests.
- For large hedges, use a broadcast spreader to ensure even coverage.
Watering is critical after application. If the granules sit on dry soil, they won’t break down. The water carries the nutrients down to the root zone where the tree can actually use them.
How Much Fertilizer To Use
More is not better. Over-fertilizing can cause salt buildup in the soil, which burns the roots and turns the foliage brown. Always follow the instructions on the package for the specific brand you are using.
As a general rule, use about one pound of actual nitrogen per 1,000 square feet of root zone. For a small tree, this might be just a handful of granules. For a large hedge, you will need considerably more.
Common Fertilizing Mistakes To Avoid
Even experienced gardeners make errors with arborvitae. These trees have shallow, fibrous roots that are sensitive to harsh chemicals. Avoiding these mistakes will save you from a lot of heartache.
Fertilizing In The Fall
Fall fertilizing is a major no-no. It stimulates new growth that won’t have time to harden off before winter. This new growth is tender and will likely die back, leaving your tree looking ragged and stressed.
If you missed the spring window, wait until the following year. Do not try to make up for it in the fall. The tree needs to focus on going dormant, not on producing new leaves.
Using Weed And Feed Products
These combination products are designed for lawns, not for trees. The herbicides in them can damage the roots of your arborvitae. Always use a dedicated fertilizer for your trees and shrubs.
Keep lawn fertilizers away from the root zone of your arborvitae. The high nitrogen content in lawn food can cause rapid, weak growth that is prone to breakage and disease.
Ignoring Soil PH
Arborvitae prefer slightly acidic to neutral soil with a pH between 6.0 and 7.0. If your soil is too alkaline, the tree cannot absorb nutrients even if they are present. A simple soil test can tell you if you need to adjust the pH.
If the pH is off, fertilizing is a waste of time and money. Correct the pH first with sulfur or lime, then apply fertilizer. This ensures the nutrients are actually available to the plant.
Special Situations For Container-Grown Arborvitae
Arborvitae grown in pots have different needs than those in the ground. The soil in containers is more prone to nutrient depletion and temperature swings. They require a more consistent feeding schedule.
For container plants, use a slow-release fertilizer in early spring and then a liquid feed every four to six weeks during the growing season. The frequent watering that pots require washes nutrients out of the soil quickly.
Always water your container arborvitae before applying liquid fertilizer. This prevents the roots from burning. Also, make sure the pot has adequate drainage to prevent salt buildup from the fertilizer.
Fertilizing Newly Planted Arborvitae
If you just planted an arborvitae, resist the urge to fertilize immediately. Newly planted trees need time to establish their roots. Fertilizing too soon can actually harm them by forcing top growth before the roots are ready.
Wait until the second spring after planting to begin a fertilizer regimen. At that point, the tree has established a decent root system and can benefit from the extra nutrients. For the first year, just focus on consistent watering.
Watering And Fertilizing Relationship
Fertilizer and water work together. Without adequate moisture, the tree cannot absorb the nutrients. Without nutrients, the water alone won’t produce lush growth. You need both for a healthy arborvitae.
After you fertilize, ensure the tree gets about one inch of water per week. If you have a dry spring, you may need to water more frequently. Deep, infrequent watering is better than shallow, frequent watering.
Mulching around the base of the tree helps retain soil moisture and keeps the roots cool. Use a two to three inch layer of organic mulch, but keep it a few inches away from the trunk to prevent rot.
Seasonal Fertilization Calendar
Here is a quick reference for the entire year. This schedule works for most climates and soil types. Adjust the dates based on your local frost dates and weather patterns.
- Early Spring (March-April): Apply slow-release granular fertilizer.
- Late Spring (May-June): No feeding needed, just regular watering.
- Late Summer (August-September): Apply a light second feeding.
- Fall (October-November): No fertilizer, focus on deep watering before ground freezes.
- Winter (December-February): No feeding, protect from heavy snow and ice.
This calendar gives your arborvitae exactly what they need when they need it. It aligns with the natural growth cycles and prevents the stress of over or under feeding.
Frequently Asked Questions
Can I Fertilize Arborvitae In The Summer?
It is not recommended to fertilize during the hot summer months. The heat stresses the tree, and the fertilizer can burn the roots. If you missed the spring feeding, wait until late summer or early fall for a light application.
What Is The Best Fertilizer For Arborvitae?
A slow-release granular fertilizer with a high nitrogen content, such as a 10-8-6 formula, is ideal. It provides steady nutrition without the risk of burning the shallow roots. Organic compost is also an excellent, gentle option.
How Often Should I Fertilize My Arborvitae?
Most established arborvitae only need one feeding in early spring. A second light feeding in late summer is optional but can help boost winter hardiness. Over-fertilizing is more common than under-fertilizing.
Why Are My Arborvitae Turning Brown After Fertilizing?
This is likely due to fertilizer burn. The salts in the fertilizer have damaged the roots. Flush the soil with plenty of water to dilute the salts. In the future, use less fertilizer and water it in thoroughly.
Should I Fertilize Arborvitae Before Planting?
No, you should not fertilize at planting time. Mixing fertilizer into the planting hole can burn the new roots. Instead, amend the soil with compost and wait until the second spring to start a fertilizer program.
Final Thoughts On Feeding Your Arborvitae
Getting the timing right is the most important part of fertilizing arborvitae. Early spring is your primary window, and late summer is your secondary one. Stick to this schedule, use a slow-release product, and water deeply after application.
Your arborvitae will reward you with dense, vibrant green foliage that provides privacy and beauty for years to come. Pay attention to the signs the tree gives you, and adjust your approach as needed. A little care at the right time makes all the difference in the health and appearance of your evergreen investment.