How to Grow and Care for Vitex (Chaste Tree)
by Ken Lain, the mountain gardener
This Arizona favorite is the ideal small flowering tree for mountain landscapes. It blooms in a profusion of lavender-blue flower spikes in summer that attract butterflies and hummingbirds. Large enough to use as a focal point in the front yard and behaved enough to use as a patio or street tree. Plant them in rows to create a fragrant summer screen or use them as a specimen near entryways.
The Vitex, Vitex agnus-castus, is popular in landscape design for its deer and javelina-proof qualities. It goes by many names, including Chaste Tree, Sage Tree, and Monk’s Pepper. It is a small decorative tree with a multi-stemmed or vase-shaped habit. It produces fragrant, upright spikes of flowers in mid-to-late summer. The foliage is palmately compound, resembling hemp, and emits a sage-like fragrance when crushed. This tree has a fast growth rate, often gaining 1-2' feet per year. It's best planted in the early spring or autumn.
Tree Specifications
· Botanical Name: Vitex agnus-castus
· Plant Type: Flowering Deciduous Tree/Shrub
· Mature Size: 15' feet tall x 12' feet wide
· Sun Exposure: 6+ hours of mountain sun
· Soil Type: Well-drained; thrives in poor soil
· Flower Color: Lavender, blue, purple
· Hardiness Zones: 6–9
· Native Area: Mediterranean, Central Asia
Vitex Care
Vitex is a hardy, long-lived tree that requires very little maintenance once established. Growers love it for its heat tolerance and spectacular late-season color when other trees have finished blooming. In terms of care, plan to water your tree throughout the growing season, April through October, if rainfall is insufficient. This tree benefits from regular feeding and occasional pruning to maintain its shape. Unlike some fruit trees, it is not considered a "messy" tree.
Soil
Vitex prefers well-drained soil and is remarkably tolerant of poor, rocky soils. While it can handle neutral to slightly alkaline pH, good drainage is absolutely essential; Vitex will suffer in soggy, wet, or heavy clay soil.
How to Plant
1. Dig a hole 2-3 times the width of the container but the same depth.
2. Score the root ball sides and bottom with a utility knife or pruners and place it in the planting hole.
3. Blend Watters Premium Mulch into the native soil at a ratio of 1 part mulch to 2 parts native soil and pack firmly around the roots.
4. Sprinkle 7-4-4 All Purpose Plant Food around the planting area.
5. Prevent 'Transplant Shock' by adding Watters "Root & Grow" to your water at 2-week cycles for the first 2 months.
6. Use the remaining Watters Mulch inside the tree well as a top dressing to suppress weeds and insulate roots.
Light
Vitex is incredibly tough and tolerates mountain wind, even on exposed ridgelines. It performs best in full sun (at least 6 hours); the more sun it receives, the more prolific the summer blooms. While it can tolerate partial shade, it will result in fewer flowers and a leggy habit.
Water
Water newly planted trees regularly for at least the first month (2 months if planting in Summer). Automatic irrigation may not be enough for the initial establishment.
· April – Oct: Irrigate 2 x weekly
· Nov – Mar: Irrigate 2 x monthly
Fertilizer
Feed 4x times per year to encourage heavy blooming and vigorous growth.
· Spring: 7-4-4 All Purpose Food + Soil Sulfur
· Summer: 7-4-4 All Purpose Food + Humic
· September: 7-4-4 All Purpose Food
· December: 7-4-4 All Purpose Food
Pruning
This tree is very forgiving. Simply prune in late winter or early spring to maintain your desired shape. You can "deadhead" spent flower spikes in mid-summer to encourage a second flush of blooms.
Pests and Diseases
Vitex is remarkably pest-resistant and generally ignored by deer and javelina. The primary issue to watch for is root rot if the soil does not drain properly. Ensuring good airflow and proper site selection will prevent most problems.