Proper irrigation to your plants during the summer months is crucial. As the temperatures rise, plant watering needs will also increase. However, adjust your watering schedule if your garden receives a deep, substantial rain event.
Observe plants regularly for signs of water stress. Some signs to look for include: wilting, curling leaves, yellowing or falling of older leaves, and dead stems or branches. Some plants with larger leaves like Sacred Datura (Datura wrightii) and Queen’s Wreath (Antigonon leptopus) will often wilt during the hottest part of the day, but by next morning they usually recover. However, if they do not recover by the following morning, it is a good indication they need to be watered.
The amount of water and watering frequency depends on many factors. These include: soil type, weather (temperature, humidity, rainfall, etc.), microclimates, cultural practices, plant size and species, and whether newly planted or established in the landscape (two years or more).
Below are general guidelines to help you determine how much and how often to water your landscape and container plantings to keep them healthy when rainfall is lacking. Native and desert-adapted plants that were newly planted and those that are not established in the landscape need to be watered until they become established in the landscape and can then survive with natural rainfall.
Even established plantings will need an occasional supplemental watering during long periods of drought to keep them healthy and stress-free.
Established native or desert-adapted trees should be watered at least once a month if no rainfall. If the temperature is over 108 degrees, water your native or desert-adapted trees at least twice during the month. Always allow soil to dry out between each irrigation cycle. Water at least 3 feet deep for your trees.
Established native or desert-adapted shrubs should be watered every two to three weeks. Always allow soil to dry out between each irrigation cycle. Water at least 2 feet deep for your shrubs.
Natural rainfall may be adequate for most well-established cacti and succulents. However, if rainfall is insufficient, water may be needed at least once for cactus and twice for succulents during the month of July. Always allow soil to dry out between each irrigation cycle. Water your cacti and succulents to a depth of at least 8-12 inches.
With increased humidity and higher temperatures, careful watering of non-native succulents during this time is a must.
Established native or desert-adapted herbaceous perennials, groundcovers and vines should be watered every 2 weeks and at least to a depth of 1 foot. Always allow soil to dry out between each irrigation cycle.
During the summer native and desert-adapted trees can be planted. See What to Plant section for more details. After planting your trees, they should be watered immediately and the moisture monitored for the next few days to keep the root ball from drying out. Newly planted native and desert-adapted trees may need to be watered more frequently until established. It can take up to 3-5 years for trees to become established in the landscape.
Recently planted native or desert-adapted trees should be watered once a week if temperatures are over 100 degrees. If temperatures are over 108 degrees water every 2-3 days. Unestablished trees that have been in the ground for 2 to 5 years water every 10 days.
Shrubs should be watered once a week if temperatures are over 100 degrees during their first year in the ground; over 108 degrees water every other day. Water your shrubs during the second year every 10 days if temperatures are over 100 degrees; every 3 days if over 108 degrees. Water your shrubs to a depth of at least 2 feet. It can take up to two years for your shrubs to become established in the landscape.
During the summer cacti and other warm-season succulents can continue to be planted. See What to Plant section for more details. When planting cacti and succulents, it is imperative to wait a week before watering to minimize the chance of rot. After the initial irrigation of your succulents, allow the soil to dry out and water every 10-14 days. Cacti need to be watered once more after initial watering, but allow the soil to dry out between watering. Cacti and succulents can take about a year to become established in the landscape.
Unestablished native or desert-adapted herbaceous perennials, groundcovers and vines should be watered once to twice weekly if temperatures are over 100 degrees; if over 108 degrees water every other day and water to a depth of at least 1 foot. Herbaceous perennials, groundcovers and vines usually take about a year to become established in the landscape.
Herbs may need to be watered twice weekly and vegetables may need to be watered every 2-3 days. For most vegetables it is important to keep the soil moist around the root zone during its growing season. Don’t allow the soil to dry up too much as this can affect the growth of the plant and quality of the fruit. Provide shade and apply mulch to your herbs and vegetables if needed.
Agaves and other succulents (Aloe spp., Madagascar Palm [Pachypodium lamerei], Ponytail Palm [Beaucarnea recurvata], Slipper Plant [Pedilanthus macrocarpus], Euphorbia spp., Haworthia spp.) in large containers should be watered at least once to twice this month. Cacti in containers should be watered at least once this month. However, cacti and succulents in smaller containers may need to be watered more often especially cacti and succulent seedlings.
Many winter-growing succulents including Succulent Geraniums (Pelargonium spp.), Iceplants (Malephora spp., Drosanthemum spp.,Cephalophyllum spp.), Living Stones (Lithops spp.) and crassulaceous plants (Kalanchoe spp., Cotyledon spp., Echeveria spp, Dudleya spp.) have become inactive. These summer-dormant succulents need to be watered less during the summer months. Water carefully and allow the soil to dry out between watering.
Keep an eye on your warm-season annuals and herbaceous perennials in containers. Water them at least two to three times weekly particularly if they are planted in smaller containers.