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.

Alternative weed control

Yellow cast of one kind of herbicide

With all of the rains we’ve had, weeds are having a ball. Whether you are a homeowner or landscape contractor responsible for commercial landscaping, using chemical weed killers does not have to be your only choice for weed control. It is important to understand why this is important.

Are weed killers safe? In short, no, although some products insist the weed killing chemical in their sprays do not hurt humans or wildlife. Sadly, they aren’t giving you the whole picture. While the jury may still be out on the main ingredient for some, it is most definitely in when it comes to the so-called inert ingredients.

Inert chemicals in weed killing sprays are toxic. According Crystal Gammon in a June 22^nd, 2009 Environmental Health News article, inert chemicals in Roundup, a popular herbicide, are more deadly than the herbicide itself. The additive known as polyethoxylated tallowamine, is particularly poisonous to human embryonic cells. It is also toxic to cells making up the placenta and umbilical cord.

Think about this: Hundreds of thousands of gallons of Round-Up are used every day to spray common areas, roadsides, and yards. Not only does this end up in our groundwater, every time you walk outside, you, and even your pets, have the potential to pick up residual spray on shoes and paws, bringing it into your home. Traces of herbicides can be found on your floors, carpets and furniture. Your pets ingest the stuff when they lick their paws. Scary.

There are at least two products currently available to control weeds that do not harm people, pets and wildlife.

A “weed flamer” is very effective in controlling weeds, and also has the bonus of killing weed seeds before they germinate. The weed flamer works by boiling water in plant cells, causing them to burst. This is the first step to weed killing. While passing the flame over the weed, you also burn weed seeds on the ground. It is important to remember when using this tool to only use it on small, green weeds. Obviously, if you try and burn large, dead weeds you risk setting fires. This is no toy, and requires the utmost care when using, but is highly effective. It is especially useful along edges of driveways, sidewalks and in areas of landscape rock. Red Dragon currently holds the patent for a weed flamer. You can find it on their website, or in some Ace Hardware stores.

Another simple weed killer is vinegar. Although store bought vinegar with 5% acidity will work, you may have to spray more than once. However, with horticultural vinegar coming in at 20% acidity, it works much quicker. Adding a squirt of dish soap helps, too, binding the vinegar to the leaves. Dish soap also acts like tiny magnifying glasses, intensifying the sun’s rays and burning the leaves ever more. Comparing the price of chemical weed killer to a gallon of horticultural vinegar will also sell you on the idea even if you don’t care about toxic chemicals in your yard. Horticultural vinegar is available on Amazon.

Although it sounds very old-fashioned, a stirrup hoe is a very effective way to keep weeds under control. This hoe, shaped like a stirrup, slips under weeds disturbing a minimal amount of soil. This is important so you don’t accidentally plant more seeds to come up later while hoeing. As with any weed control, getting weeds out when they are small is the key to less effort.

Another option is to “solarize” your soil. In late spring, cover a weedy area with CLEAR 5 mil plastic. Secure the edges with weights, or bury edges with dirt. That’s it! Leave the cover there for at least 2 months. This will kill all weeds and weed seeds; however, keep in mind it will also kill beneficial insects, soil microbes…everything. This is important if you are solarizing a garden area.

Some folks swear by pre-emergents, as they are intended to keep weeds from germinating in the first place. Aside from the high price, it is just another chemical added to our groundwater after a heavy rain. An alternative to chemical pre-emergents is corn gluten meal. Non-toxic and safe, corn gluten inhibits weed growth and will not poison your yard in the process. As a side note, it is thought that using pre-emergents are directly related to increase populations of mites. Another good reason to remember how closely everything in the world is related. Kill one thing, affect another. And not necessarily in a good way.

We all have a responsibility to the health of our planet, and if going green is high on your list, put away those poisons and do the right thing when controlling weeds. Your children’s children will thank you.

Tree pruning tips

Trees in nature get along quite well without pruning. In fact, they don’t care if they are ever pruned at all.

The only reasons trees are pruned are for people. Here are some acceptable reasons to prune trees:

1.      Clearance. We raised the canopy of trees so we can sit, walk or park underneath. We prune limbs to keep them off of our roof, or from coming into contact with power or phone lines.

2.      Aesthetics: We shape trees so they are more symmetrical. While we often remove dead branches, this does not improve the health of a tree, nor make them grow better. In fact, if you want bird life to visit your yard, leave the dead branches. Birds prefer their trees ‘un-messed’ with.

3.      Mistletoe: Mistletoe often attacks mesquites and other landscape trees. While a tree can live a very long life with mistletoe, I recommend removing it. Because mistletoe is a parasite, it will eventually kill the tree. And as it does so, it makes for a very ugly and sickly-looking plant.

4.      Vista Pruning: We prune trees in order to maintain views.

How do you know if your tree needs pruning and can you do it yourself? That depends on the age, size, species and location of the tree. The larger the tree and the more extensive the pruning needs are, the more likely you will need to hire a certified arborist for a consultation. Do you really need a professional? Yes, you do. If you hire someone without proper training, they could well ruin your tree forever.

Regular maintenance can often be accomplished by a homeowner. Here are some tips for do-it-yourself tree care:

1.      Newly planted trees should NOT be pruned at planting time except to remove broken or crossing branches. All branches on the lower part of the trunk should be left on for at least two years. This will ensure sturdy trunk growth to help the tree stand on its own.

2.      Raise the canopy by removing small branches before you ever remove large branches. Removing a two-inch diameter limb leaves a serious wound. Always assess each cut before removing more. As you release the weight by cutting off branches, you may find you’ve raised the canopy enough without the need to cut more. You want to remove the fewest number of branches to get the job done. Always prune to point of origin—do not “hedge” cut a tree.

3.      Do NOT leave coat-hangers—those ugly long stubs. Always cut back to the point of beginning.

4.      Do NOT cut into the trunk. This damages the cambium layer, the living part of a tree’s trunk. All cuts should be made to stay outside of the “branch protection zone”—a ridge of bark that surrounds where the branch is attached to the tree.

5.      Never remove more than 25% of the canopy in one year. Because older trees have a harder time with extensive pruning, aim for no more than 10% in those cases.

6.      NEVER top a tree. Topping a tree means cutting of the central leader back to a branch that cannot assume the role of a leader. If your tree is blocking your view, growing too tall, getting into power lines—there are options—including selective thinning, raising the canopy, or waiting for the tree to grow out of the view. If these are not an option or don’t work, have it removed. Trees CANNOT be shortened without ruining them forever.

Visit the International Society of Arboriculture website to learn more about tree care.

What's the difference between native, drought tolerant, and desert adapted plants?

Maybe you have heard these terms in relation to plants grown in the Tucson area and thought they were interchangeable. Or maybe at least you knew what one or two meant. Actually, the meanings are not necessarily interchangeable, and in some cases they mean completely different things.

By far the best plant choices, if you are looking for a low water and maintenance landscape, are those considered native to the area. Just keep in mind that not all Arizona native plants will survive in all parts of Arizona. For example, the Fremont cottonwood is native to riparian areas, but it is not a good choice as the water requirements are over 250 gallons per day for a mature tree. That’s not smart water use. Ponderosa Pines are right at home in Northern Arizona and in the mountains of Southern Arizona, but that doesn’t mean they will grow in Tucson.

Drought tolerant plants are those species that thrive on minimal irrigation. This does include native desert species, but not exclusively. For example, the Texas Ranger, even though not native to Arizona, is quite drought tolerant and happy in high heat and cold temperatures.

Desert adapted plants are those adapted to some desert conditions; but the caveat is not necessarily our desert. There are many deserts in the world, all of which contribute species to our list of choices, but many can’t take our freezing temperatures, blazing summer sun, or alkaline soils.

The best way to assure you are selecting plants that will not require excessive amounts of water or protection from frosts is to research what is hardy before buying. The Sunset Western Garden Book is worth purchasing, even if a used book, as it contains thousands of plants with detailed descriptions of the plant, where it is from, and where it will grow. In addition, unlike the USDA Hardiness Zone Map, which treats the United States not only as though it is flat, but ignores latitude, Sunset’s Climate Zone Maps are more realistic. Sunset’s Climate Zones take into account latitude, microclimates, valleys and mountains, which makes sense when you consider that the USDA lumps Tucson and Seattle into the same zone. Go figure.

Cactus choices for flowers

Argentine Hedgehog

It is easy to forget how dramatic our desert cactus are. For most of the year, they just kind of sit there and blend in with the desert. Cactus make great additions to desert landscaping even when they are not blooming, but if flowers are what you are after, here are some stunning choices.

Engelmann's Prickly Pear

The Engelmann’s Prickly Pear is one of our most common cactus species. The bright yellow flowers are following by red fruits relished by birds.

Santa Rita Prickly Pear

The Santa Rita Prickly Pear is named after the Santa Rita Mountains in Southern Arizona. The purple pads add color even when the plant is not sporting yellow flowers. It’s interesting to note that botanists don’t really know exactly why the pads are purple. Some think it’s tied to cold weather, some to drought stress, others to genetics. Whatever the reason, if pays to buy a very purple one to begin with.

Engelmann’s Hedgehog is a notable native, with stunning magenta flowers on a small, compact plant.

Look to the pincushion species for flower shows to rival all others. Hot pink flowers are easy to spot from long distances, even though the plant is under 6 inches tall.

Arizona Fishhook

The stately sahuaro is a summer bloomer, with white flowers appearing on the top, sides and arms. Pollinated by bats, these flowers produce delicious fruits still harvested the traditional way by Native Americans.

Although not a native, the Argentine Giant handles heat and cold, but it does prefer part shade in the hot desert. The flowers are white, and up to six inches across. The Argentine Hedgehog is another hardy cactus from the same region. Taller than other hedgehog species, the stems reach up to two feet tall. The flowers are an amazing red-orange, and also up to six inches across.

Cactus need little care, and will suffer if you give them too much care. Avoid watering cactus in the ground unless they are drought stressed. Container cactus, however do need water—weekly in the summer if they are in full sun.