Best Fertilizer for Arborvitae: What to Use and When

Quick answer: Established arborvitae often do not need fertilizer when growth and needle color look normal. If growth is slow or needles are pale or short, feed in early spring, before new growth starts, with a complete (N-P-K) fertilizer where nitrogen is the highest number, such as 20-15-15 or 10-5-5, at about 1 pound of product per 100 square feet of root area. Water it in, and never fertilize drought-stressed plants.

Do arborvitae need fertilizer?

Not always. University of Minnesota Extension says that if growth rate and needle color are normal for the variety, fertilizing is not necessary, and that evergreens generally need less fertilizer than deciduous trees (UMN Extension). A soil test is the best starting point because it shows what your soil actually lacks. UMN also notes that most soils already have enough phosphorus.

Signs fertilizer may help

• New growth is sparse or slow.
• Needles are not a healthy green or are shorter than normal.
• The plants are in very sandy or heavy clay soil.
• The plant was badly damaged by insects or disease.
• You want to encourage faster growth in young plants.

Before you fertilize, check that the soil is not dry, because fertilizer should not go on drought-stressed plants. If you suspect disease, see our guide to common arborvitae diseases.

When to fertilize arborvitae

Fertilize in early spring, before new growth begins. UConn’s Home and Garden Education Center recommends fertilizing arborvitae in early spring, following soil-test recommendations (UConn). UMN gives a window from before new growth expands (early April in Minnesota) to about mid-July at the latest. After that, new growth may not have time to harden off before cold weather and is more likely to suffer winter dieback.

Minnesota dates do not map directly to Texas. The Bell County Texas Master Gardeners’ monthly checklist advises waiting until spring to fertilize trees and shrubs, and lists October through January as the time to plant trees and larger shrubs (Bell County Master Gardeners). For a central Texas garden (zone 8b), that points to spring, as growth begins, rather than fall.

Water dry plants before you fertilize, and apply before a good rain if you can. Do not fertilize drought-stressed plants, because fertilizer can burn stressed roots.

Newly planted arborvitae: slow growth in the first season is normal while the plant re-establishes. Focus on watering and mulch, and let a soil test tell you whether feeding is needed later.

What fertilizer to use

UConn recommends a high-nitrogen fertilizer such as 20-15-15 or 10-5-5. UMN says a complete fertilizer, one that supplies nitrogen (N), phosphorus (P) and potassium (K), is often recommended, and that the nitrogen number is usually the highest because nitrogen leaches through soil and needs replacing most often.

Type	Notes
Granular (complete N-P-K)	UMN calls fertilizer spikes and root feeders more costly than standard granular products. Spread granules under the branches and water in.
Fertilizer spikes	Convenient, but each spike holds only a small amount, so they are not cost-effective compared with granular (UMN).
Liquid through a root feeder	Works on all but heavy, poorly drained soil; on sandy soil it leaches quickly and may need repeating through spring and early summer (UMN).
Compost or well-rotted manure	Adds a small amount of nutrients as mulch breaks down (UMN).

How much fertilizer to apply

UConn gives a simple rule: about 1 pound of fertilizer per 100 square feet of root area. UMN expresses rates as actual nitrogen: a common maintenance rate is 2 to 4 pounds of actual nitrogen per 1,000 square feet, applied every 2 to 4 years, and for mature, slow-growing trees about 1 pound is probably enough. The table converts the UConn rate to actual nitrogen (our arithmetic).

Fertilizer	Product at 1 lb per 100 sq ft	Actual nitrogen per 1,000 sq ft
20-15-15	10 lb per 1,000 sq ft	2 lb
10-5-5	10 lb per 1,000 sq ft	1 lb

Worked example (our arithmetic from the UConn rate): a shrub whose branches cover 4 feet by 4 feet is 16 square feet. 16 divided by 100 times 1 pound is 0.16 pound, about 2.5 ounces of 20-15-15. Always follow the product label if it differs.

At 2 pounds of actual nitrogen per 1,000 square feet or less, UMN says you can use a drop spreader under the branches and slightly beyond. Higher rates can burn the grass underneath.

How to apply fertilizer, step by step

1. Measure the area under the branches and slightly beyond; that is the root area to feed.
2. Water first if the soil is dry.
3. Spread the fertilizer evenly over the whole root area. Do not leave piles, which can damage feeder roots.
4. If the plant is mulched, spread the fertilizer right over the mulch.
5. Water it in well.
6. If the weather stays dry, keep watering regularly through late fall.
7. Keep a 3 to 4 inch layer of mulch, starting at the root flare and extending outward.

Healthy soil makes fertilizer work better. See our garden soil guide for how to improve heavy or sandy soil.

Common mistakes

• Fertilizing when growth and needle color are already normal.
• Fertilizing drought-stressed plants.
• Applying late in the season, which pushes tender growth that may not harden off before winter.
• Piling fertilizer in one spot instead of spreading it.
• Guessing the amount instead of measuring the root area and using the label rate.

Frequently asked questions

When is the best time to fertilize arborvitae?

Early spring, before new growth begins. In a Minnesota-style climate that can run to about mid-July at the latest; for central Texas, local Master Gardener guidance says to wait until spring.

Do arborvitae need fertilizer every year?

No. If growth and needle color are normal, fertilizing is not necessary. When it is needed, a common maintenance rate is repeated only every 2 to 4 years (UMN).

What fertilizer ratio is best for arborvitae?

UConn gives 20-15-15 or 10-5-5 as examples of a high-nitrogen fertilizer. A soil test will show whether your soil needs more than nitrogen.

Can you fertilize arborvitae in the fall?

UMN advises not applying regular fertilizer after mid-July in Minnesota, but says a slow- or timed-release fertilizer can be applied from late summer until late fall to a nutrient-stressed plant. In central Texas, local guidance is to wait until spring.

How much fertilizer does one arborvitae need?

About 1 pound of product per 100 square feet of root area (UConn). For a shrub covering 16 square feet that is roughly 2.5 ounces of 20-15-15.

Does this apply to Emerald Green and Green Giant arborvitae?

UMN’s guidance covers evergreens in general and UConn’s covers arborvitae, so the same principles (soil test first, early-spring feeding, moderate rates, no feeding of drought-stressed plants) apply to popular varieties such as Emerald Green and Green Giant. Check the product label for exact amounts.

Sources

• UConn Home and Garden Education Center: Arborvitae
• University of Minnesota Extension: Fertilizing evergreens (reviewed 2026)
• Bell County Texas Master Gardeners: Monthly Gardening Checklist

Guidance from Connecticut and Minnesota applies as general principles; timing varies by region, so check with your local extension office.