Southwest Gardening: Managing July Plants

What to Plant in July

We recommend most plants be planted in the fall or spring.  However, if you must plant during the summer months watering may need to be more frequent and you must be diligent about observing your newly planted plants for signs of water stress.

Many cacti and warm-season succulents can still be planted in the summer. When transplanting cacti and succulents, mark either the south or west side and plant facing the orientation you marked to avoid the burning of tender tissues. Most nurseries will mark the side of the container to help you determine proper planting orientation.

However, if the original orientation is not known, newly planted cacti and succulents need to be covered with shade cloth if the plant surface appears to yellow or pale suddenly. Use a shade cloth rated between 30-60% as anything higher will block most of the sunlight and will not be suitable for your cacti and succulents. You may need to keep the shade cloth on the plant for the duration of the summer to prevent sunburn.

• Prickly-pears (Opuntia spp.)
• Barrel cacti (Ferocactus spp.)
• Hedgehogs (Echinocereus spp.)
• Easter Lilies (Echinopsis spp.)
• Pincushions (Mammillaria spp.)
• Chollas (Cylindropuntia spp.)
• Golden Barrel (Echinocactus grusonii)
• Senita (Pachycereus schottii)
• Organ Pipe (Stenocereus thurberi)
• Mexican Fence Post (Pachycereus marginatus)
• Queen of the Night (Peniocereus greggii)
• Old Man of the Andes (Oreocereus celsianus)
• Agaves (Agave spp.)
• Aloes (Aloe spp.)
• Red-yucca (Hesperaloe parviflora)
• Giant Hesperaloe (Hesperaloe funifera)
• Burseras, Elephant Trees (Bursera spp.)
• Pencil Tree (Euphorbia tirucalli)
• Candelilla (Euphorbia antisyphilitica)
• Carrion Flowers (Stapelia spp.)
• Slipper Plant (Pedilanthus macrocarpus)
• Madagascar-palm (Pachypodium lamerei)
• Elephant Food (Portulacaria afra)
• Ponytail Palm (Beaucarnea recurvata)
Desert-adapted trees can be planted during the summer months if you follow the guidelines in the Watering Section above. When planting native and desert-adapted plants, it is usually unnecessary to back-fill with soil amendments and vitamins or to add rooting hormones. Remember to remove nursery stakes from trees after planting.
• Desert Willow (Chilopsis linearis)
• Mesquites (Prosopis spp.)
• Palo Verdes (Parkinsonia spp.)
• Texas-olive (Cordia boissieri)
• Anacacho Orchid-tree (Bauhinia lunarioides)
• Texas Ebony (Ebenopsis ebano)
• Palo Blanco (Mariosousa willardiana syn. Acacia willardiana)
• Golden Leadball Tree (Leucaena retusa)
• Ironwood Tree (Olneya tesota)
• Catclaw Acacia (Senegalia greggii syn. Acacia greggii)
• Palo Brasil (Haematoxylon brasiletto)
• Mexican Ebony (Havardia mexicana)
• Kidneywood (Eysenhardtia orthocarpa)
• Desert Fern (Lysiloma watsonii)
Shrubs should be planted in fall or spring.

Herbaceous perennials and groundcovers should be planted in fall or spring. However, many warm-season vines can be planted during the summer months. Water immediately after planting and monitor the moisture for the next few days to keep the root ball from drying out. Water newly planted native and desert-adapted vines twice to three times weekly to a depth of at least a foot. Gradually extend the time between watering and monitor plants regularly for signs of water stress.

• Yellow Orchid-vine (Callaeum macropterum)
• Queen’s Wreath (Antigonon leptopus)
• Arizona Grape-ivy (Cissus trifoliata)
• Old Man’s Beard (Clematis drummondii)
• Purple Bushbean (Macroptilium atropurpureum)
• Yellow Morning Glory-vine, Yuca (Merremia aurea)
• Passionflowers (Passiflora spp.)
• Slender Janusia (Janusia gracilis)
• Arizona Canyon Grape (Vitis arizonica)
Planting of cacti seed can continue. Seed can be soaked overnight in water to help begin the germination process.  Place seed in a well-draining soil mix (½ quality potting soil and ½ perlite or pumice) and lightly cover. Keep soil moist until germination occurs.
• Armenian cucumbers
• pinto beans
• black-eyed peas
• tepary beans
• snap beans
• muskmelons
• cantaloupes
• pumpkins
• winter squash
• sweet corn
Pepper and tomato seed may be planted indoors and transplanted in August or September for a fall harvest.

Wait until fall or spring to plant most herbs.


Pruning, Fertilization, Problems, July Plants


Pruning should be done to maintain plant health (remove dead, damaged or diseased portions, cross branching, etc.), to highlight the “natural” shape of the plant, to train a young plant, and to eliminate hazards. Excessive or heavy pruning causes significant stress to trees and shrubs.

The best practices are to prune the least amount necessary and prune for legitimate reasons. How much to prune depends on the size, species, age, as well as your intentions.

Two good principles to remember–a tree or shrub can recover from several small pruning wounds faster than from a single large wound and never remove more than 25% of the canopy in a year. For more information register for a Garden class on pruning that will teach you the proper pruning techniques for trees and shrubs or visit for information on proper pruning of young and mature trees.

Lightly prune native and desert-adapted trees to avoid breakage during the summer thunderstorms in July and August if needed. Do not prune excessively as this will expose the tree trunk to the blazing sun causing it to sunburn.

Pruning newly planted trees is not recommended and in fact, can be detrimental. However, at planting time prune broken or torn and diseased branches. Save other pruning actions for the second or third year. For more information on developing a healthy tree visit

Prune your cacti if necessary to maintain size, for propagation or to remove a damaged or diseased stem; prune at joint or segment. Use a sharp, clean pruning tool and spray tool periodically with a 70% alcohol solution to prevent infection.

If the pruned stem is to be used for propagation, allow the cutting to dry out for a week before planting.

Continue to prune old flowering stalks from Hesperaloes (Hesperaloe spp.), Agaves (Agave spp.), Yuccas (Yucca spp), and Aloes (Aloe spp.).

To encourage continued flowering, deadhead herbaceous perennials such as Desert Marigold (Baileya multiradiata), Chocolate Flower (Berlandiera lyrata), Texas Blanket (Gaillardia pulchella), Red Sage (Salvia coccinea), Angelita Daisy (Tetraneuris acaulis), Mealy Cup Sage (Salvia farinacea), and Tickseeds (Coreopsis spp.).


Most native and desert-adapted plants in the landscape do not generally require fertilizer as they are adapted to our soil conditions.  In most cases, fertilizers are generally applied to prevent deficiencies.  If fertilizers are needed, one application for the year is usually sufficient. The best time to fertilize landscape plants are in March, April or the early part of May.

We do not recommend fertilizing your desert-adapted landscape plants during the summer months.  Fertilizing will cause excessive, luxuriant growth that requires more water and new growth is too tender to take the excessive heat and sun exposure.  Wait until next spring to fertilize, if needed.

Periodic fertilizing may be needed for plants in containers as nutrients in the soil will have diminished over time.  Always follow directions on the label.

Continue to fertilize your warm-season annuals and herbaceous and woody perennials in containers if necessary.

Cacti and warm-season succulents in containers should be fertilized at least once during the month depending on the type of fertilizer used.  If using a slow-release granular fertilizer for your cacti and succulents in containers, fertilize in late March and again in July or early August.

Do not fertilize any winter-growing succulents such as Succulent Geraniums (Pelargonium spp.), Iceplants (Malephora spp., Drosanthemum spp.,Cephalophyllum spp.), Living Stones (Lithops spp.) and crassulaceous plants (Kalanchoe, Cotyledon, Echeveria, Dudleya) as they are summer dormant.

Continue to water and fertilize your Karoo Roses (Adenium spp.) to promote bloom through the warm season.

Continue to fertilize your vegetable and herb garden as needed.


Mosquitoes are now commonplace throughout the Valley, particularly after rain events. Be sure to empty any containers, buckets, bowls, etc. that might catch rainwater as the larvae require water in which to mature.

Ants and termites are swarming and if you see the mud tunnels of termites crawling up your plant stems, just wash them off. They are not harming the plants.

Defoliation of many landscape plants can occur with the appearance of a high infestation of grasshoppers. Population size varies year to year and they are a difficult insect to control in the garden. When population numbers are low, hand-pick and remove. If an infestation is high, use a protective cloth or floating row cover to protect your plants. Allow natural predators such as birds, lizards, and spiders to help keep the population under control.

Whiteflies are small, sucking insects that are often found on many ornamental and vegetable plants. Plants infested with whiteflies show symptoms of sticky, yellowing leaves and when the plant is disturbed the small insects will fly generating a white “blur”.  There are many species of whiteflies and they are abundant at different times of the year.  Whiteflies are difficult to manage and insecticides are not recommended as it can disrupt and destroy their natural enemies. If you choose to use an insecticide, use an insecticidal soap or oil to help control populations.

Large, green caterpillars may be appearing on tomatoes, eggplant and even the Sacred Datura (Datura wrightii). They can either be the tobacco or tomato hornworm feeding on the leaves, flowers, and stems. After three to four weeks of feeding, the larva will burrow into the soil to pupate.  In about two months, the large adult moth will appear and are often mistakenly identified as hummingbirds.

These moths are important pollinators for many nighttime flowering plants including the Sacred Datura (Datura wrightii), Fragrant Evening Primrose (Oenothera caespitosa), and the Queen of the Night (Peniocereus greggii). No method to control is necessary. If an infestation is high, hand-pick caterpillars off your plants or allows naturally occurring parasites to help control the population.

A white, cottony mass may appear on ornamental and edible plants and is sometimes confused with cochineal scale because they too produce a waxy, white cottony substance but it is most likely mealy bugs. Both insects feed on plant juices, however, cochineal scale feed exclusively on cacti such as Prickly-pears (Opuntia spp.), Nopalea spp. and Chollas (Cylindropuntia spp.).

Mealybugs are often difficult to control and systemic insecticides may be used, but are not always effective. However, usually dipping a cotton swab with a 50-50 mixture of rubbing alcohol and water solution and then wiping on these insects can help manage the population. Mealybugs are also a common problem for many cacti and succulents grown indoors or in greenhouses and are often found either on the stems or roots.

Take the infested plant(s) outdoors during the summertime as this seems to help get rid of these pests. It takes constant vigilance to keep them under control.

The male cicadas’ mating calls are a cacophony of sound that permeates the desert air and often heralds to the gardener that summer has arrived. The Apache cicada is common to low-desert regions and the adult has a mostly black body with a pale band behind its head. The nymphs spend almost their entire life underground feeding on the roots of many desert trees, shrubs and other ornamentals.

As the nymph becomes an adult, it will then surface from the soil and undergoes one last shedding of its exoskeleton. The adult cicada will feed on the plant sap of many trees or shrubs. After mating, females will make small “hatch” marks on the slender tips of trees or shrubs to lay their eggs. This physical damage can cause the tips to “die” back, but is not detrimental to the plant and is often thought of as “natural pruning”.

There is no need to control cicadas as they are part of the desert ecology. Allow natural predators to control the population as many birds and lizards find the cicada nymph and adult to be a tasty treat.

If it has been a dry season, rabbits may be nibbling on plants that they may not have eaten before. Most mature plants can handle rabbit sampling, but newly planted plants should be protected until they have attained a larger size.  Protect plants with a wire cage or spray Liquid Fence TM to help deter these animals. Allow mesquite pods to fall and remain on the ground for rabbits to eat as they are a vital food resource for many desert animals. It might even help distract them from eating your most prized plants.

Cochineal scale, the cottony, white substance on your Prickly-pears (Opuntia spp.) and Chollas (Cylindropunita spp.) may be active now. Remove by using a fast stream of water or spray insecticidal soap.

Adult ocotillo borers are now active in search of stressed or recently planted ocotillos in which to lay their eggs. The eggs are laid in the bark and the larvae or grubs excavate into the stems causing a hasty decline of the plant. Look for signs of borers by watering the ocotillo during the warm season. If the stems do not leaf out, examine for grubs and remove any infected stems by pruning back to the base of the plant.

The large, black-brown beetle bumbling onto your porch during the sweltering summer nights is the Palo Verde Beetle. It has just emerged from its subterranean home looking for a mate.  For the past two to four years it has lived underground as a grub or larva feeding on the roots of many native and non-native plants, not just Palo Verde trees as the common name suggests.

When the grubs become adults they will ascend and can be seen in late June, July, August, and September, particularly after rainfall.  Once the female adults’ mate, they lay their eggs and die soon after making their lifespan of about one month. Using pesticides is not recommended as the beetle is already gone by the time you notice any damage.

To prevent root borers keep your plants as healthy as possible as they will be less vulnerable to an attack.  There are many natural predators of the adult beetle including roadrunners, coyotes, owls and even bobcats. Grubs are eaten by skunks.


Watering In July

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 the 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 the 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 the 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 the 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.