Your how-to watering guide for all of the plants in your garden. New plantings, establishing trees and shrubs, watering annuals and perennials, how to keep your veggies happy, we cover it all!

Establishing New Plantings

All plants require supplemental water until their root systems are established. This takes a full growing season.

Watering deeper and less frequently is recommended to encourage a deeper root system.
Plants that are watered more frequently but for less time each watering will develop a shallower root system that is more prone to drying out.
Watering by hand with a watering can, setting a hose at the base of the plant on low with a timer set, or using drip irrigation are all good ways to water plants while they are establishing in the garden.
For the science behind why deeper and less frequent drinks are best, read our article on how soils store moisture.

Helping Plants Thrive in the Garden

It is important to remember that every plant has different watering requirements. Cowichan Valley is a Mediterranean climate so plants that are not drought tolerant require regular watering (even after establishment) in order for them to thrive and grow to their fullest potential, especially in June, July and August. Established plants do not require supplemental water during the cooler months of October to April. Drip irrigation is an efficient way to water; it keeps foliage dry which reduces the risk of disease, and greatly reduces a gardener's workload.

Watering Trees and Shrubs

Trees and shrubs should be watered in their container before being planted, and again after planting.

Until plants are established they will require regular watering. For plants that are not drought tolerant, a general rule of thumb is that larger plants should be watered deeply once a week (two times a week during hot spells of above 25 degree Celsius weather) one of the following ways:

A hose on dribble for an hour
One to two buckets of water slowly poured over them
A drip irrigation system two to three times per week for 30-45 minutes each time

It is important to check the moisture of your soil by hand to ensure that the water is penetrating the soil. Dig down next to plants 6-8 inches to accurately determine soil moisture. It is not enough to dig down the first 2-3 inches as sometimes mulch can hold more moisture than the top soil below it.

Commonly Used Garden Shrubs and Trees

As summers get hotter and drier many shrubs and trees that have historically been able to grow without irrigation in Cowichan Valley will no longer establish and thrive without watering and irrigation. We are also seeing established plants decline in health or become more susceptible to pests and diseases due to drought and heat stress.

The following is a list of commonly used trees and shrubs we see suffering from lack of irrigation. This shows up as more pest and disease issues such as Andromeda lace-wing (for Pieris shrubs), powdery mildew, aphids, etc. It also results in decreased growth, lack of flowering, leaf drop, and decreased vigour. These plants may survive a summer or two of drought, but they will never thrive and perform their best. For ideal plant growth, irrigation or supplemental watering is required.

Azalea, Leucothoe, Pieris, Rhododendron, Vaccinium and other ericaceous shrubs
Camellia, Daphne, Hydrangea, Nandina, Himalayan Sweetbox (Sarcococca), and Skimmia
Redbud (Cercis), Dogwood trees, Japanese maples, Magnolia, and flowering cherries
Roses, heathers, and grasses
Confierous plants: Fir (Abies), False Cypress (Chamaecyparis), Japanese Cedar (Cryptomeria), Spruce (Picea), and Cedar (Thuja)

** Note, this is not a comprehensive list of garden plants that require supplemental water.

Watering Perennials and Annuals

Perennials

Perennials should be watered thoroughly in their container before being planted, and again after planting. Until plants are established they will require regular watering. Check the soil moisture by sticking your finger in the ground. The first 2-3 inches of soil should dry out between waterings.

Smaller plants in 4 inch containers are more prone to under and over watering. Their root systems should never be allowed to dry out completely but it is also important to not keep the soil and their roots water-logged from overwatering. Soil is too wet to water if, when rolled into a small ball and squeezed, water drips from your hand.

The ultimate watering requirements of perennials is incredibly variable and depends on the species, light and soil texture it is growing in.

Annuals

Watering annuals planted in garden beds is the same as watering perennials.

Annuals planted in containers require watering every day to once a week depending on container size and weather. Soil should be allowed to dry out between waterings (to reduce the likelihood of root rot), but the soil should not be so dry that it peels away from the side of the container. Generally annual planters in the sun cannot be left multiple days without water so take this into consideration when planning summer holidays.

Annuals in the shade are more prone to being overwatered as they take longer to dry out than annuals in the sun. Touch the soil between waterings to ensure it is not too wet.

Tips to reduce watering requirements of annuals:

Use saucers to hold water that drains from the planter
Use larger containers so that soil takes more time to dry out between waterings
Use glazed ceramic planters or plastic planters as these containers do not wick moisture from soil
Micro irrigation systems can be installed for annuals

Watering Vegetable Gardens

Vegetable starts: Soil should not be allowed to dry out and consistent moisture is required for most seeds to germinate. A hose nozzle with a mist or shower spray setting is optimal. Vegetable starts are prone to drying out and may need watering twice per day during hot and dry weather. The presence of fungus gnats (small flies) and mold or algae growth on the soil surface can be indications of overwatering.
Direct seeding: Seeds require consistent moisture to germinate. Carrot seeds are by far the most sensitive to drying out and watering the surface of the soil twice per day may be required for germination.
Newly planted seedlings: Newly planted seedlings benefit from hand watering before and after planting.
Watering the vegetable garden: Once vegetable plants are growing, drip irrigation (10 to 30 psi) is ideal because it delivers water directly to the roots of plants and it keeps foliage dry which helps prevent powdery mildew, blight, and other fungal or disease issues. Drip systems in vegetable gardens are generally scheduled for 20 to 45 minutes daily to every third day during the summer months. Watering requirements will vary based on the soil texture and light levels.

Soil Texture

We have covered how to water plants, but plants are only part of the equation. A garden is also made of soil and soil texture plays a huge role in how much gardeners need to water. A soil’s ability to retain water, known as its water-holding capacity, is controlled by its texture and the amount of organic matter in the soil.

Soils with smaller particles (clay and silt) hold more water and for longer than soils with larger particles (sand).
Soils with a sandy texture drain much faster so they don’t need to be watered for as long, but need to be watered more frequently.
Soils with heavy clay are more prone to becoming waterlogged. They should be watered for longer, but less frequently than sandy soils.
Organic matter greatly increases the water holding and storing capacity of soils. It has a high water-holding capacity due to its porous structure and ability to absorb and retain moisture.
In coarse textured soils (sand), the challenge is to improve water retention. In fine textured soils (clay), the challenge can be poor drainage. In both cases increasing organic matter content can benefit the soil so it can support healthy plant growth.

To determine the texture of soil you can use a jar test.

The best way to spend less time watering is to choose plants best suited to your site, install a drip irrigation system, and amend your soil with organic matter.

Click here for plants with very low watering needs. Click here for plants that require no supplemental summer irrigation.

Proper Care: Watering