How To Fertilize, Prune And Water A Vitex Chaste Tree

Chaste trees, scientifically known as Vitex agnus-castus, are beautiful flowering trees that are exceptionally easy to grow and care for. With proper pruning they will repeat flower into early fall.

Here's a breakdown of what you need to know regarding feeding, pruning and watering chaste trees...

Fertilizing A Chaste Tree

Chaste trees are light feeders however benefit from fertilization. 

When to fertilize a Chaste Tree?

I fertilize my chaste trees in late winter or very early spring.

What type of fertilizer?

When feeding my chaste trees, I use a slow-release shrub and tree fertilizer at rates recommended on the product label. Alternatively, you can feed with mild, organic plant food.  Avoid the use of 10-10-10 and other similar quick-release fertilizers as this can cause excessive foliage growth. 

To conserve moisture throughout the growing season and suppress weed growth, I also always apply a 1 to 2" layer of cured, shredded or chipped wood mulch or pine straw around the tree in late winter. As the mulch decomposes it will add vital nutrients to the soil that your chaste tree will appreciate.

Note:  Avoid the use of freshly chipped wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot. 

How much fertilizer? 

This will depend of course on the size of the tree you are fertilizing and the type of fertilizer. Regarding slow-release shrub and tree fertilizers, you'll find application instructions on the package label. 

Where to spread the fertilizer? 

The root system of a chaste tree might grow 2 to 3 feet deep but the majority of the feeder roots responsible for absorbing nutrients are in the top 12 to 18 inches of soil. Spreading fertilizer on the soil surface is sufficient to reach these feeder roots. 

Spread fertilizer evenly around each tree, beginning a couple feet from its trunk, and then one foot beyond the drip line (branch perimeter) for every 5 feet in tree height. 

Note:  If the soil is compacted or subject to excessive water runoff, the fertilizer can be applied in a series of holes 6 to 8 inches deep in the same area with about five holes per 1 inch of trunk diameter.

Soil pH

Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. 

Chaste trees prefer a moderately acid to neutral soil ranging from 6.0 to 7.0 on the pH scale.  Once you know the soil pH, if necessary, you can adjust it to meet the needs of your Vitex.

Testing Soil pH
If you're unsure about the pH of your soil, and whether or not it's suitable for growing chaste trees, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with a inexpensive soil test kit or pH tester probe. 

To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.

How To Water A Chaste Tree

Chaste trees prefer a moist but well-drained soil. That said, when established they are more tolerant of dry or wet periods. 

Here's some helpful watering tips...

Summer Watering

At planting time

Water deeply at planting time, making sure the soil around the root ball and the root ball itself is moist all the way down to its base. Then, each day thereafter, check the soil moisture and only provide water if the soil has dried out somewhat or is just lightly damp. After several days of checking soil moisture you should establish how many days you can wait between waterings. Now you'll have a watering schedule. If there's a good soaking rain you can count this as a watering.

Note:  Before removing your chaste tree from it's nursery pot and planting, it is beneficial to soak the root ball.

During the first growing season

After planting a chaste tree in the ground, especially during the hotter summer months, the tendency is to think it has to be watered every day in order to grow roots and become established in its new home. However, in average garden soil you should not have to water your newly planted chaste tree every day. More often than not, this causes constantly wet soil conditions that can lead to root rot. In the absence of sufficient rainfall water only as needed to keep the root ball and surrounding soil damp to moist. Keep in mind that deep soaking less frequently is much better than splashing just a little water around the tree every day. Deep soaking promotes deep root growth and can reduce water loss by evaporation. 


When established, chaste trees are quite drought tolerant. I rarely water mine except to provide an occasional deep soaking in an extended summer drought. If during a drought leaves start to fall from your chaste tree this is an indicator your tree could use a good deep soaking. 

Winter Watering

During the cooler winter months chaste trees won't require as much attention to watering. Provide water only if necessary to keep the soil damp.

At planting time

When planted during the winter, deep soak the soil and the root ball after planting. Then check the soil moisture every few days until you've determined how many days or weeks go by until the soil has dried and water is needed. With average rainfall you may not need to water trees again until spring or summer.

Note:  If you have an automated irrigation system it's best to cut it off during the winter, only running it manually on occasion and only when and if necessary. Provide water during the winter only if there's been a prolonged period of dry weather.

How & When To Prune A Chaste Tree

Chaste trees do not require pruning however respond very well to it. You can prune your chaste tree to control size or for shaping purposes, and also to encourage repeat flowering using a type of pruning called deadheading.

Maintenance pruning

Damaged or dead branches or stems should be removed when they occur. Make your cut beyond the point of breakage or dead part.

For controlling size or shaping

Extensive, heavy pruning to reduce the size of a chaste tree should be done in late winter, before new growth has begun to emerge. At this time, you can cut branches to a desired length or to a point where they intersect another branch. If you are just shortening a branch, cut just above a twig or bud. Keep in mind that new growth will take off in the direction of the twig or bud. If you are removing an entire branch see the illustration below for where to make you cut.

Note:  There is really no need to use wound paint or tar after making a cut. Trees will heal themselves.

For tree forming

Chaste trees can be grown as a shrub or pruned to form a tree. I usually wait until a chaste tree is 4 to 5 feet tall before starting the tree forming process. Tree forming is quite straightforward. In late winter, before new growth begins to emerge, simply remove lower limbs and branches to desired height. See illustration below for where to make cuts on larger branches. 

Note:  I remove lower branches to a height that allows people to walk under the tree. That said, before removing a branch take time to study where it goes. Make sure that its removal won't spoil the shape of the canopy. Depending on the size of a branch, you'll use bypass hand pruners, lopping pruners, or a tree saw to remove branches.

Tip:  If you have any reservations about pruning a mature chaste tree call your a local arborist. Pruning mature trees may require special equipment, training, and expertise. An arborist can provide a variety of services to assist in performing the job safely and reducing risk of personal injury and damage to your property. They are also able to determine what type of pruning is necessary to maintain or improve the health, appearance, and safety of your trees.


After the first flowering cycle in late spring or early summer, spent flower stems can be snipped off before they start to form seeds. To remove a spent flower from your chaste tree, simple use bypass pruners to make your cut at the base of the flower stem. If you allow your chaste tree to grow to full size, deadheading becomes impractical. 

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