Before deciding to add a saguaro into the landscape, consider the following:
Do you have a sunny location? Saguaros require full sun at maturity. Although smaller saguaros (under four feet) or newly planted may require some shade in summer.
Is there enough space as it grows and matures? Although a single stem or “spear” may look small at planting, over time the saguaro will grow arms. Planting too close to structures such as the house will become problematic over time. Pruning off the stem to fit the space is not recommended.
Will the roots be able to expand? Saguaro roots are very shallow and don’t go deeper than 20 inches, but they do expand horizontally as much as they can, in nature they will go up to 50 feet from the trunk.
Is the location safe? Saguaros have many spines and can weigh several tons at maturity. Keep saguaros away from pathways, driveways and areas of activities. Planting at a safe distance is recommended to limit the potential damage to humans, animals and structures.
Are there high-water plants such as a lawn, fruit trees or vegetable gardens nearby? Saguaros need water, but they do not require the amount of water used by high-water plants. Select plants that have similar watering requirements as a saguaro including brittle bush, bursage, desert milkweed, globemallow, pink fairy duster and creosote.
In case of failure, how will it be removed? Saguaros are a long-term investment, and if they fail or become damaged consider how it will be removed. Could it be left to decay on the premises? Will professionals have easy access for removal or correction?
Saguaros in Arizona are protected by native plant laws. It is illegal to remove saguaros from national and state parks, or other public lands except by permit issued by the Arizona Department of Agriculture. Removal without a proper permit is a felony and can result in a fine of up to $150,000. A permit is not required when moving a saguaro in the same property or transporting nurserygrown plants.
For more information, visit agriculture.az.gov/plantsproduce/native-plants
Before purchasing a saguaro, ensure it is grown legally, comes from a reputable source and relocated plants are tagged with a permit.
Successful planting and establishment depend on the size of the saguaro. The smaller the size of the plant, the higher chance of survival following planting (Arizona Game and Fish, 2019). Transplanting success is much higher with smaller “spears” less than 10 feet tall. Larger plants require professionals and special equipment to move and transplant due to their size and weight.
The Saguaro Desert Gardening Guide is for homeowners planting one-tofive-gallon container plants or for bare root plants under four feet tall. For more information about planting large saguaros, visit Arizona Game and Fish Best Management Practices
Planting Techniques
Saguaros can be planted in spring after the danger of frost has passed and throughout the growing season (March through October). Planting during the hottest part of the year requires checking the newly planted saguaro periodically to ensure its planting success.
For container plants, gently remove the plant using old pieces of hose or carpet. Remove the soil media from the saguaro roots to plant bare root. Locate the topmost structural or horizontal roots. The depth of the hole should be from the bottom of the roots up to the horizontal or structural roots.
Do not plant too deeply. A common and incorrect practice is to plant saguaros too deeply to compensate for their top heaviness. To find the appropriate planting depth, locate the point where the stem meets the roots. Alternatively, you can look for the spot where the stem narrows just above the soil surface. This will help you determine the correct planting depth. If the plant needs stability, then temporary support will be required. See Arizona Game and Fish Best Management Practices for more information about providing support to large saguaros. Incorrect planting will cause a slow decline and even death of the plant.
Ideally, the width of the hole should be at least two to three times that of the root system. The loosened soil will allow the developing root system unrestricted growth in the landscape soil.
Whether the plants were container grown or transplants, replant the saguaro facing the same direction, at which it was growing, to avoid sunburn. Young saguaros in the desert usually germinate and develop in the shade of a “nurse plant” such as a Palo Verde tree, so young cactus from the nursery may still need to be protected from the summer sun for a few years. Protect young and newly planted plants by applying (30 to 60 percent) shade cloth during the summer and remove when the weather has cooled, usually mid to late October.
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To plant, lightly wrap the saguaro with old pieces of hose or carpet. Do not grab by the roots. Gently place the plant upright in the hole. If the hole is too deep, fill it in with native soil until you have the correct soil depth. Do not add gravel to the bottom of the planting hole. This can create a perched water table leading to drainage problems.
Backfill the hole with native soil (soil that was removed from digging the planting hole). Do not add soft fill or amendments to the planting hole. Lightly tamp down soil to remove any air pockets and ensure good root-tosoil contact.
After planting, it is best not to water the saguaro for a few (2 to 4) weeks. Roots most likely have been damaged at planting. Allow the roots to callus over before watering to decrease the chances of root rot.
About half of the transplanted saguaros don’t survive, especially when transplanting a big, old saguaro. It can take up to 4-5 years to fully establish, but the plant is so rich in water and nutrient reservoir that it will stand still for a good amount of time, giving the impression that is fully adapted to the new site.
After Planting Care
During the months of April through October, the newly planted saguaro will benefit from additional water at least once per month, especially in the lower, hotter desert areas. A saguaro may lose up to 30 to 50 percent of its mass while re-growing roots (AZ Game and Fish, 2019). Saguaros do not need to be on a drip system. Apply water with a slow drip from a water hose around the plant. Be careful not to allow water to accumulate at the base of the plant or be kept constantly wet. Water to a depth of at least six to 24 inches. Always allow the soil to dry out between each watering cycle.
It is possible the saguaro will dehydrate after planting. Saguaro pleats will shrink as the plant loses water. However, with irrigation it should begin to hydrate existing roots and develop new roots to absorb water from the soil. The expansion of the pleats and/or new growth at the top is a good indicator of water uptake.
Once the summer rains arrive, watering should stop unless the weather becomes hot and dry again. Stop watering in the fall and winter when temperatures are milder. It may take up to two to four years for the saguaro to become established in the landscape.
If newly planted saguaro begins to turn yellow, cover immediately with shade cloth. Keep the cloth on the plant for the duration of the summer.
Mature or Established Plant Care
Average Sonoran Desert yearly rainfall is usually sufficient for mature plants. They rely on warm-weather rains (monsoon) for their reproduction and survival but will harvest and store water from winter rains. Most of the saguaro’s growth occurs during the warm season.
These plants are adapted to live in the desert and should not receive excessive amounts of water. However, during long periods of droughts or extreme heat waves, they may need supplemental irrigation (see Saguaro and Heat Stress) below.
If supports or bracing were installed at planting time, they should be removed after two years. However, before removing, an evaluation must be done to ensure the plant has developed a strong root system and is able to stand upright without the use of a support.
Saguaro and Heat Stress
Saguaros have many adaptations that allow them to survive and thrive in hot, dry conditions. The Sonoran Desert has two rainy seasons (summer and winter) when plants not only receive water, but the cloudy conditions during summer season alleviate daytime heat stress.
The period just before the summer monsoon is usually when saguaros are under the most stress because they have little or no soil moisture from which to extract water. Therefore, they must draw on the internal water reserves until monsoon rains recharge the rooting zone with moisture.
When critical high temperatures are reached or exceeded, plant cells will experience chemical alterations, membrane disruptions, dehydration and death. Even cactus have their limits on how much heat they can take and then develop heat-related symptoms. Symptoms include stems dropping, stems becoming yellow, orange or brown, dehydration, rotting and even death.
Extremely hot temperatures lasting consecutive days in a row might irreversibly damage internal tissues. Extended periods of high nighttime temperatures affect the cactus’ ability to photosynthesize efficiently, reducing the amount of food (energy) they can produce.
Extreme heat during the day compounds the stress of cactus by damaging photosynthetic tissues. Saguaros also have a limited capacity to cool their photosynthetic tissues through transpiration because their small pores, called stomata that exchange water vapor and carbon dioxide are closed during the day, when thermal stress is high.
Stem temperatures can be many degrees higher than ambient temperatures during the day. In combination, lack of monsoon rains can lead to dehydration and weakening of the structural integrity of the plant.
In the Phoenix-metro area, many saguaros are suffering from heat-related stress. These urbanized areas experience higher temperatures than outlying areas. Urban areas can be up to seven degrees higher than natural desert areas. Structures such as buildings and roads absorb and re-emit the sun’s heat causing urban “heat islands.” For more information, visit Environmental Protection Agency on understanding urban heat islands at www.epa.gov/heatislands
How can you help your saguaro during heat waves?
Place shade cloth, if possible, on yellowing areas immediately.
Be proactive and water only if necessary. If your saguaro is dehydrated from lack of water, apply water once a month. Remember to keep moisture away from the base of the plant and allow soil to dry out before the next irrigation.
A dehydrated saguaro doesn’t always indicate lack of water. It could also indicate the plant does not have any roots or root problems such as rot, preventing water from being taken up by the plant. Check soil moisture as this will help you determine the cause of dehydration.
Do not water if the plant is hydrated. A hydrated plant will be plump, and the pleats will be widely spaced apart. Overwatering can lead to rot and once this begins it will be hard to treat.
Do not fertilize. Saguaros are adapted to desert soils.
Do not prune off stems.
If stems break off the plant, allow the wound to callus over and air dry. Do not stuff it with fabric or spray it with sealers.
If the saguaro is planted in a gravel landscape or surrounded by hardscapes, consider planting understory plants with similar watering requirements. Plants to use include brittle bush, globemallow, bursage, creosote and desert milkweed. Try to mimic the natural growing environment of the saguaro.
Remember always exercise caution when working around saguaro especially if stems have dropped. There is always the potential for more stems to drop or for the plant to collapse. Despite your best efforts, you may not see the extent of the damage for many months or years.
You can help the Garden by participating in the Saguaro Census at dbg.org/saguaro-census/. Help Garden scientists better understand the effects of climate change and increased temperatures in urban areas on the saguaro.
A cactus size can influence its susceptibility, and the bigger plants with more mass are more prone to the effects of heat and drought. Larger and older plants have more arms, and thus, tend to be the first to start to lose their integrity. (Hultine, 2023).
Saguaro Problems
Many saguaro problems arise from incorrect care or environmental stressors. Below are some common problems encountered when growing saguaros in the landscape.
Overwatering is a common practice with plants becoming over inflated. Many times, the epidermis will split and crack. The plant will form a callus and the area will become permanently damaged. These splits can also become an entry point for pathogens. Overwatering can also cause roots to rot. Rotting can rapidly spread throughout the plant tissues.
Wind and storms can topple saguaros, especially those with multiple arms. Heavy rains coupled with strong winds, may even cause a saguaro to lean or drop stems. If a large saguaro falls over, most of the time it splits in half and most likely cannot be righted.
Though the plants are sensitive to frosts and freezing, well-established plants appear to survive unscathed from a few hours of below-freezing temperatures. This resistance is attained mainly by their large mass that provides a lengthy time lag to reach equilibrium with ambient temperature (Yetman et al. 2020). However, consecutive days of freezing temperatures can cause injury to the plant. The topmost portions of the plant are the most sensitive to injury although a dense mat of spines can help to insulate. Unfortunately, evidence of injury or even mortality may not be evident for months or years after the freezing event. Cover young saguaros with frost cloth if freezing temperatures are predicted. Frost cloth can be left on the plant for a couple of days but should be removed after frost event has passed. Stems may become reddened with cold but usually will revert to green as temperatures warm. Symptoms of frost damage can include rot or stem dieback.
Sun damage occurs when the chlorophyll (green pigment) degrades or breaks down. The tissue becomes yellow or orange. If sun damage becomes severe, the area will become brown, crack and die. If caught early, the sun damage could be reversed by covering it with shade cloth. Preventing sun damage is essential for the health of the plant. Permanent damage to the stem caused by sun damage reduces the surface area for photosynthesis to occur.
As saguaros age, bark injuries, also termed epidermal browning, start appearing on the stem surfaces, resulting in blackish, rough skin (Yetman et. al. 2020).
Epidermal browning begins on the south side of the stem and spreads around the base of the plant. It occurs as the plant ages and is exposed to a variety of hazards including the deleterious effects of UVB radiation. Since the area is no longer able to carry out photosynthesis, over time the saguaro will succumb to old age. The correlation between browning may be a part of the normal aging process which accelerates in some individuals (Turner & Funicelli, 2000).
Saguaros can become infected with a common bacterial pathogen naturally found in the desert environment. The Erwinia bacteria can be found in the soil and can be spread by birds, insects and other vectors. An infected saguaro will exhibit symptoms of oozing, smelly black liquid, discoloration of tissue, lesions or soft spots on the epidermis. Sometimes an infection can develop in a saguaro through an injury or as a result of frost or heat damage. It may be long after the actual event, but brownish or black ooze coming out of the trunk or stem will indicate a problem. Healthy saguaros have the ability to contain the spread of localized infected areas. Weaker plants suffering from other stresses can be more susceptible to the disease. There is no preventative treatment for bacterial necrosis, and it is important to prevent wounding to plant tissue as this can be an entry point for the bacteria.
Regularly inspect your saguaro for wounds and if the plant is infected, treat immediately. Scrape out rotting black tissue with metal spoon. Once you see, fresh green to white tissue, spray with a solution of one part bleach to three parts water solution to disinfect the fresh tissue and allow to air dry. Check periodically. A successful excision will show a brown callus forming. Bacterial necrosis is now thought to be just the natural decay of cactus tissues killed or weakened by something else, such as epidermal browning (Wentworth, 2021). Adding powdered horticultural sulfur to wound can help to form callus and prevent the infection to advance.
Termite tunnels are commonly found on saguaro stems during the summertime. They are not harming your saguaro but actually removing any dead tissue. No need to treat or prevent termites from doing their natural duty.
Rooting Saguaro Stems
Fallen stems do occur and many times we wonder if they can be rooted. It can be attempted, with mixed success. We recommend allowing the cut end to air dry and callus over. Dust a rooting hormone to bottom end and place cutting in a pot with either pumice or perlite. Keep soil slightly moist and cover cutting with shade cloth. It may take several months or even a year for roots to form.
References
Arizona Game and Fish. 2019. Best Management Practices for Saguaro Translocation and Replanting.
Hultine, K., Hernandez-Hernandez, T., Williams, D., Albeke, S., Tran, N., Puente, R., Larios, E. 2023. Global Change Impacts on Cacti (Cactaceae): current threats, challenges and conservation solutions. Annals of Botany.
Turner, D. & Funicelli, C. 2000. Ten-Year Resurvey of Epidermal Browning and Population Structure of saguaro Cactus (Carnegiea gigantea) in Saguaro National Park. The University of Arizona.
Wentworth-Lazaroff, D. 2021. Book of answers. 1st Ed. Arizona- Sonora Desert Museum.
Yetman, D., A. Burquez, K. Hultine, M. Sanderson. 2020. The Saguaro Cactus: A Natural History. The University of Arizona Press.