Choosing the right planting container

 

 

Container planting is a great way to add interest to special areas such as your front entry or an intimate patio. Keep in mind, however, that not all planting containers are created equal. In the desert southwest, the best pots are the ones that don’t get too hot for plant roots, and that can take winter freezes without falling apart.

Plastic pots, including the new heavy duty composite versions that look like clay, last a long time, but they do have their drawbacks. When sitting in full sun, they get very hot, often to the point that the side of the pot that gets the most sun will prevent roots from growing there. In addition, while it is good they don’t dry out as fast, they also tend to hold too much moisture. Therefore it is important to always check the soil moisture level before adding more water. If you are currently determining if a container plant needs more water by touching the surface of the soil, this is a mistake, especially for large containers. If the soil is wet just a few inches below and you add more water, you can easily suffocate the roots with oversaturation. A gadget called a moisture meter (about $5-$8 in home improvement stores) is a worthwhile investment. The gauge tells you if the soil is dry or wet to a depth of six to eight inches (the length of the probe), not just at surface level.

Avoid buying pottery from Mexico, as although it is inexpensive, it is not worth the low price since they will disintegrate quickly. This type of pottery is fired at a low temperature. Low fired clay absorbs moisture inside and out, crumbling into nothing after just a few freeze/thaw experiences. Coating the inside with waterproofing material does not make any difference, as the exterior will still absorb rain and expand with heating and cooling.

High-fired Italian clay, glazed pottery and concrete planters are good choices, but each have features to consider before purchasing.

Italian clay is high-fired, making it quite durable. It is also known as Terra Cotta. These pots dry out quicker, so will need more water during the hot summer. However they breathe well, allowing roots to get the oxygen they need.

Glazed pots are coated with melted glass, which requires high firing temperatures. This is a wonderful way to add color to your landscaping no matter what you plant in them. They are pricey, but worth it. They will last a very long time. The options are wide, and what works best depends on your intent. While the ones with patterns and decorations are lovely, solid colors draw attention to the plant, not the pot. However, they do not breathe because of the glaze, so be careful not to over-water.

Concrete planter options are best for large plants. They are very expensive and require special delivery and equipment to set up…so make sure you know exactly where you want them because moving them around is not easy! Phoenix Precast Concrete is the only company I’ve found with a variety of shapes, sizes and colors. They do breathe somewhat, but also be careful not to over-water.

Planting in containers gives you so many options. Depending on the type and size, they can serve as focal points and entry statements. They can also make gardening easier, allowing you to move them around for proper sun exposure, and reach without bending and stooping. Planting containers can be higher maintenance in the sense that you will need to water more often and occasionally change the potting soil, but for many the convenience and joy they bring exceeds the maintenance.

Got agave problems? It may be this common pest.

The agave is one of my favorite plants. Nothing quite compares to its dramatic form, making it a great choice to add interest in desert landscaping. While both low water use and normally maintenance-free, the agave does succumb to an annoying insect that decimates the entire plant with little notice that there is a problem until it is too late.

The symptom of snout-nosed agave weevil damage almost looks like the plant is wilted from lack of water.

However, this is not the case. What has happened is that the weevil has chewed a hole into the center bud of the plant. While doing so, they excrete an enzyme that softens plant tissue, allowing bacteria, fungi and diseases to take hold. When the female lays her eggs, the white grubs that hatch eat the plant from the inside out. This process takes 2 to 3 months. Once you see the damage, the plant is dead and there is nothing you can do to save it. I’m not a proponent of systemic insecticides, which you may read is an option. I prefer to recommend you avoid the species of agave that is the most susceptible to snout-nose agave weevil attacks: the Century Plant. (Agave Americana, photo)

Proper plant care also reduces susceptibility to insects and diseases. With agaves, less water is more. Over-watering these plants, if it doesn’t cause roots to rot, speeds up their growth, shortening their lives. When an agave reaches maturity, it will flower and die. And despite what you may have heard, cutting off the flower stalk will not make it live longer.

If you want your plant to live a nice, long life, anywhere from 5 to 25 years (depending on the variety), monitor the water schedule carefully. For plants in the ground, water once a week in the summer, and once a month or so in the winter, depending on winter rains. Container plants in full sun will need twice that, usually twice a week in the summer and twice a month in the winter.

Are you under or over watering your landscape plants?

Growing plants in the desert is challenging all the way around; from the heat to cold to minimal rainfall, getting plants to thrive can be frustrating. If you are puzzled as to how to tell if you are over or under watering your landscaping in the desert southwest, here are some guidelines.

It is frustrating to try and figure out what your plants want, as by the time they show symptoms in many cases, it’s too late to save the plant. Do not wait too long, however, or you may lose most of your plants.

Under and over watering symptoms often overlap, creating even more frustration. Evaluating symptoms carefully, however, will guide you in the right direction.

Under watering symptoms include loss of plant vigor, wilting, yellow leaves, leaf curling or drop, pest attack, stem and branch dieback and eventual death. Over watering symptoms include leaves yellowing, leaves smaller than normal, chlorosis (both iron and nitrogen), slow decline, soil-borne pathogens, and eventual death.

If your home was built within the past few years, chances are pretty good your irrigation timer is set for initial planting. After the first few months, the irrigation system should have been rescheduled. In this case, almost guaranteed your plants are being over watered. If you are a minimalist and either don’t have an irrigation system or try to water by hand, chances are pretty good you are not watering enough or deep enough.

Although desert plants are drought and low water specialists, most do need some periodic irrigation to look their best. Just don’t kill them with kindness (water).

It's time to adjust your irrigation schedule

As we approach November, it’s getting close to time to reset irrigation controller. Why should you bother? Wasting water never makes sense. The average home in my community uses 200 gallons per day. It may not sound like much, but add that up over a year, and that’s 73,000 gallons. Forty percent of that is typically for outdoor watering. That’s nearly 30,000 gallons per year. With the water situation here at critical levels, it makes no sense to water plants when they don’t need it.

Days are getting shorter and cooler, so plants require less water. Irrigation of desert adapted and native plants can go to once a week starting in late October. For well-established native plants (at least 3 years old) you can back off to twice a month.

There is one caveat to this, however. The only way you can change your watering schedule is if you have been watering correctly from the start. This means deep watering so the entire root system gets a good soaking. If you have been engaged in shallow watering, the root system will not be as drought tolerant, and the plant may show signs of stress if you back off.

So how to change this? Start watering your plants deeply and slowly, and over a growing season (through next summer) you will be able to adjust your irrigation in the winter months to save water. The truth is, a vigorously growing landscape plant is not happier. Studies have proven moderately stressed plants, plants that are not watered and fertilized regularly, are less prone to insect pests and disease.

A primer on biological insect controls

Bt works wonders on the tomato hornworm

There are a number of products on the market that advertise they are biological insect controllers, and it is important to understand how some of these products work. Just because a product is made from natural ingredients, does not mean it is necessarily non-toxic or safe for the environment. 

For an organic garden, you need to keep in mind what your priorities are. If you do not want to use any pesticides what-so-ever, then handpicking bugs and barriers (such as floating row covers) may be your best options. There may come a point when you need some help, and there are products out there that can do that for you.

BACILLUS THURINGIENSIS

I am a big proponent of Bt (Bacillus thuringiensis and its counterparts) as it is totally biodegradable, non-toxic to humans, pets, fish and birds. It affects the digestive system of caterpillars when they eat the treated plant. Although it will also kill caterpillars of butterflies, they rarely feed on your vegetable garden plants. To be safe, don’t spray ornamental flowers that normally attract butterflies. Another reason I consider Bt a really good product is that you can use it as a preventative. It is a “non-contact” insect killer, which means the insects don’t have to be present and you don’t have to spray the actual bug. Bt can be used on products sold as organic.

ROTENONE

Although this insecticide is made from natural ingredients, is biodegradable, but it is not non-toxic. It is a contact insecticide (you have to actually spray the insect to kill it) and is not allowed to be used on produce to be sold as organic.

PYRETHRUM

This too is a synthetic insecticide even though it is made from Chrysanthemums.  It is highly toxic to fish and honey bees. It is a contact insecticide, and considered to have a low toxicity to humans. 

SAFER INSECTICIDAL SOAP

This product is made from natural oils and animal fats and is effective against aphids, scale and other soft bodied insects. It is considered non-toxic to humans and approved for use on organic produce. The downside is if you apply it in really hot weather in a sunny location you could damage your plants. 

Common problems with cactus and succulents

Damaged by the Agave Snout-nose weevil

Cactus and succulents are relatively problem free, as long as growing conditions, soil, drainage and sun orientation are correct for the species. Always make sure you are purchasing plants are suitable for both the heat and cold. Not all of these plants can handle the brutal low elevation summer heat, or temperatures dipping into the teens. When in doubt: Plant natives!

Cochineal scale is relatively common on prickly pear and cholla. It is evidenced by cottony-like spots on the pads and stems. This insect sucks out nutrients. If left without treatment, it will eventually kill the plant. Control is simple by using repeated hard sprays of water. It’s important to catch this early, however. If the entire plant is covered with the white substance, it’s unlikely you’ll ever be able to get rid of it. It’s been to remove and replace the plant. As a side note, the female of the insect that causes the white cottony mass is the source of a red dye known as cochineal red. The red dye is used in clothing and candy, so if you are vegetarian, think twice about eating candy dyed red!

The cactus longhorn beetle attacks some columnar cactus and prickly pears leaving chewed areas on the uppermost parts. It is identified by very long antennae, as long as the beetle itself. Hand picking is considered the best control method, so you’ll need to be vigilant. The larvae will eat the inside of the plant, so they are hard to detect and control before the plant is dead.

Sahuaro rot (bacterial necrosis), is an infection caused by a number of things. It can result from sunburn, injury (including transport to planting site), frost damage, too much water and poor drainage. Bacteria spreads inside the plant before you notice what is happening. When a black, odorous liquid oozes out of the plants epidermis, it is too late to save. If this appears on an arm, removal of the arm may save it, but it must be caught before the rotting spreads into the main stem.

And what about those holes in sahuaros made by birds? Birds and sahuaros have lived harmoniously together for centuries, so trust me, the sahuaro will be fine. Those holes, usually made by woodpeckers, will later become homes for other critters, including bats and the tiny pygmy owl.

Some agave species are attacked by the agave snout-nose weevil. You’ll know you’ve got them if the leaves of the agave are laying flat on the ground. This insect prefers stressed plants (think thirsty, overwatered, too much sun, too little sun, poor drainage, temperatures too hot or too cold) and seems to prefer the Century Plant, one of the largest of the agave species. Infestation is hard to detect, and by the time the plant wilts it is too late. Remove, dig up the weevil, and kill it before replanting.

The scoop on fertilizers: Is organic better than chemical versions?

If you don't have a worm bin, you'll want one!

You might tend to think that organic fertilizers are better for your plants. However, the fact is plants can't tell the difference between organic and synthetic (chemical) fertilizers. They are both used by the plant in the same way. There are basically 3 components in fertilizers. Macronutrients are Nitrogen (N), Phosphorus (P) and Potassium (K). All 3 are usually found in commercial fertilizer in varying proportions. With organic fertilizers you typically need 3 different materials to add all 3 macronutrients. In the Tucson and surrounding communities, soils high in alkalinity (pH) can be a problem, as it binds nutrients from becoming available to the plant. This makes it even harder to deliver necessary nutrients to your plants.

Aside from the 3 macronutrients, plants also need micronutrients, which are much more difficult to find in chemical fertilizers. Micronutrient deficiencies in the soil are one of the reasons food grown today is not as nutritious as it used to be. This is where the use of organic fertilizers shine. They provide much more than the basic 3 nutrients. Organic fertilizers also improve soil structure and lower pH, which increases the availability of all nutrients.

Because each type of organic matter offers different nutritional support, you will need to add as many different kinds as you can.

Types of organic fertilizers include:

Nitrogen boosters: animal manures, plant matter (such as leaves), compost, fish meal, bat guano, worm castings and blood meal.

Phosphorus boosters: bone meal, rock phosphate

Potassium boosters: kelp meal, greensand, wood ash (depending on wood type)

Micronutrient suppliers: compost (which also contains beneficial microorganisms), gypsum (which helps break up hard alkaline soils), kelp meal and worm castings.

A new addition to the world of organic soil additives are Humates. They are touted to improve alkaline soils, but are pricey.

Sulfur can be added to soil to also correct high alkalinity, but the jury is out as to how effective this is.

While plants don't know the difference between chemical and organic fertilizers, it is important to understand that organic fertilizers last longer in the soil, and, especially when using manures and compost, create a good soil structure that retains water and encourages healthy soil organisms such as earthworms. Chemical fertilizers do not amend the soil. Period.