Planting Summer Annuals

Blooming Color This Summer

PentasOne of the advantages of living in the Southwest region is that we can have bright, colorful flowers in our community flower beds all year long. When summer brings hot temperatures, there are specific flower varieties that have adapted to the higher temperatures and alkaline soils. Specifically, choosing native plants will cost much less time, energy and money than trying to recreate flower beds from another region. Here are some tips for your summer annuals:

Prep Your Beds

Soil preparation is essential to growing summer annuals. Plan to begin preparing beds up to two weeks ahead of planting time, usually mid-May. Make sure your planting bed is well drained. The soil in the bed should be moist enough to squeeze into a ball, but still crumble with very light pressure. If the ground is too wet, you will compact the ground as you walk on it, forcing valuable air from the soil, so try not to walk on it

Next, add organic amendments such as peat moss or compost. A variety of mulches for this purpose are generally available at a local home improvement store. Spread about a 4″ layer of the mulch over the bed and mix it into a depth of 12″.

Fertilizer and fungicide can be worked into the soil at the same time. Osmocote 14-14-14 is a very good, slow-release fertilizer for the summer months. It will help keep your plants greener and healthier. Subdue is a good option for fungicide. Both of these chemicals encourage plant growth while reducing the risk of fungus growing in the soil.

Choosing Your Flowers

When your soil is ready, you can contemplate which varieties of flowers you want to plant. Dusty Miller, Pentas, Coreopsis, Celosia and 4″ Lantana are some good choices that grow well in hotter temperatures, but there are many others as well. Begonias and Zinnia are best for borders around the edge of your flower beds.

At the nursery, select the healthiest plants you can find. Younger plants are generally a better choice than tall, leggy plants that have already spent a long time in the container. Remember to choose flowers that are suited to the sunlight available at the location of your flower bed (full sun, partial sun, constant shade).

Root BallPrior to planting, water the bed well. Plant when the soil is still moist, but not saturated with water. Do not plant too deep! The stem of the flowers should be at the same depth in the bed as it was in the container. You may want to carefully open the sides of the root ball with your fingers to promote quicker root growth into the soil of the bed. Water the bed well immediately after planting and continue to water daily. In some sunny spots, you may want to water your flower beds at least twice a day.

Uncapped Emitters

Drip Irrigation

Landscape in the Southwest is populated with a broad variety of desert-adapted plants. Some, such as the Creosote Bush or the Triangle Leaf Bursage, are native to this part of the Sonoran desert. Others, such as the Texas Sage, Lantana and the Red Bird of Paradise, are not native to the area, but have proven to be able to thrive here in the Valley of the Sun. Although these are low water-use plants, they all benefit from regular irrigation in the hottest months of summer.

Miles of Irrigation

To irrigate these plants miles of underground pipes and tubes network to feed thousands of drip emitters. When activated, these emitters typically put out a flow of 1 gallon or less per hour. In some cases, an emitter with a flow of as much as 2 gallons per hour may be used. The frequency and duration of the irrigation can be controlled through a central computer or individual irrigation controllers. This allows the amount of water used to be adjusted depending on current conditions. During the monsoon season, for example, the whole system can be shut down to take advantage of the natural precipitation and save the irrigation water.


unpluggedemitterOne challenge of maintaining such an extensive network of drip irrigation is making sure the water goes where it needs to go: to the roots of the plants. Sometimes the irrigation water is emitted where there is no plant to water. You may see some of these emitters without plants from time to time as you walk through the community. How does this come about? There are several reasons: oooooooooooooooooooooooooooo

  • Normal wear and tear on the thousands of tiny plastic parts in the system.
  • Damage caused by vehicles traversing the landscape.
  • Damage caused by rodents or other animals.
  • Plant removal (both intentional and accidental).

The Solution

cappedAlthough the amount of water lost through drip emitters without plants is minute in comparison to the water used to irrigate turf areas (the bulk of water consumption!), it is still important to keep unused emitters plugged. Capping unused emitters in the landscape of large communities is an ongoing process requiring continuous maintenance. In order to stay on top of this, the landscape maintenance crews should concentrate on a different area of each maintenance cycle every week.

Drip irrigation is often programmed to run in the evening, nighttime or early morning hours. Manually turning on irrigation where maintenance crews are working allows them to see where the problems may exist. The crews should carry small plastic plugs to cap the ends of distribution tubes. If they encounter a larger leak, an irrigation technician should be called to do the repair.

What Can You Do?

Homeowners, too, can benefit from regular checks of the irrigation system in their yard. Turn your system on during daylight hours and have a look around. If you see water leaving the system where no plant is present, you may be able to solve the problem by plugging the ¼ drip tube commonly used. The appropriate plugs are readily available at any hardware store.


There are also a number of resources on the internet that can help you find information on how to maintain your plants and irrigation system.

Water Conservation Tips, Facts, and Resources –

Environmentally Responsible Gardening and Landscaping in the Low Desert –


Maintaining Citrus Trees

Citrus Fertilization 101orange trees

Citrus trees need three primary nutrients: NITROGEN – PHOSPHORUS – POTASSIUM. Phosphorus and Potassium, along with a multitude of other micro-nutrients, are in most cases sufficiently provided by the soil; however, nitrogen needs to be applied regularly.

Any kind of citrus fertilizer will provide your trees with the right nutrients, but any fertilizer with a high percentage of nitrogen will suffice. Fertilizers are labeled with the percentage of Nitrogen (N), Phosphorus (P), and Potassium (K) they contain. For example a 20-10-10 fertilizer has 20% Nitrogen, 10% Phosphorus and 10% Potassium.

When shopping for fertilizer make sure you are getting the best value for your money by purchasing the highest amount of nitrogen per dollar. If you have the choice of purchasing a 10 pound bag of 20-10-10 for $9.95 or a 10 pound bag of 12-5-8 for $8.95 the higher priced bag is a better value.

How Much Nitrogen?1108-L

You will also need to calculate the amount of actual nitrogen you will need to feed your citrus tree. To find the actual amount of nitrogen in a bag of fertilizer multiply the weight of the bag by the percentage of nitrogen. In a 20 pound bag of 12-5-8 you have 2.4 pounds of actual Nitrogen (20 x 0.12 = 2.4).

Citrus trees require an increasing amount of nitrogen as they mature. Use the table at right as a guide.

When Do I Fertilize?

The best time to apply fertilizer to citrus trees is just before they bloom, typically in January or February. You don’t want to give them their total annual nitrogen requirements at one time though. A good rule of thumb is to fertilize on the holidays – Valentines Day (mid February), Memorial Day (end of May) and Labor Day (beginning of September). This way they receive a constant supply of nitrogen when they first start to bloom, just before the heat and just after the heat.


Sunburn on Trunkssunburn vertical

One of the challenges with growing citrus trees is sunburn, especially where the trunk and larger lateral branches are exposed to intense sunlight and have not been exposed before. This causes the bark to split, crack, and peel, exposing the wood beneath to diseases and harmful insects.

To prevent sunburn, avoid pruning during the spring and summer. If it is necessary to prune, protect the exposed areas by painting the trunk with a white, water-based latex paint and water mixture or shade the trunk with a loose cloth or paper trunk wrapping. Avoid consistently moist wrappings by changing when necessary.

To treat an already damaged tree, remove any cracked or peeling bark from around the wound to allow the surrounding healthy tissue to re-grow and cover the wound. If removing bark will cause more damage to the tree, leave it in place. Also, be sure the tree is receiving adequate irrigation and watch for bacterial or fungal infection and apply fungicide according to the product label.

Water Stress

Because water carries nutrients throughout the tree, the first noticeable sign of water stress is dull, curling leaves. With continued stress, dead leaves will fall off, followed by flowers and then fruits. Surprisingly, citrus will often bloom about one month after being drought-stressed, if allowed to recover.

Rather than irrigating citrus daily, which does not allow all of the roots to get water, follow the watering intervals in the table below and utilize shade and mulch to minimize evaporation. A mature citrus tree uses about 60 inches of water a year which, depending on the size of the tree, can correspond to 17 gallons of water per day in the winter and as much as 135 gallons per day in the summer.

Applying Water

Basin irrigation is often the easiest irrigation method for the homeowner. This method uses a 4- to 8-inch high dike around the tree, at least as large as the canopy but preferably extending one foot beyond to accomodate larger roots. As the tree needs water, simply fill the basin.

Flood irrigation is used in older Arizona neighborhoods. This is very effective, but if you have grass around the tree you may need to apply additional water to wet the entire root zone.

If using bubblers, emitters or soaker hoses, be sure to buy enough to distribute the right amount around the entire base of the tree and design the system so it can expand to provide water further from the trunk as the tree grows.

Watering Intervals

Frost Damage

With preparation, most attempts to protect citrus from frost are successful. Steps that can be taken prior to the first frost or freeze are the most important. Choosing the right location for your tree is vital to its cold weather protection. A wind-protected, sunny area is the ideal location for citrus trees. Because actively growing trees are more sensitive than dormant trees, they should not be pruned in the fall, as this may stimulate new, tender growth.

Steps that can be taken for short-term protection are: covering the tree, providing additional heat, maintaining soil moisture and spraying the canopy with water.

Despite the best preparation, sometimes a tree will be damaged by frost. In this case, do not remove damaged leaves or wood until the spring growth shows the extent of the damage. See “Preventing Frost Damage” article for further information.

For more information on watering citrus visit 

References: 1. Wright, Glenn C., Protecting a Citrus Tree from Cold. The University of Arizona, AZ1222. Mar 2001. 2. Wright, GLenn C., Irrigating Citrus Trees. The University of Arizona, AZ 1151. Feb 2000.