How To Water Mature Trees

When drought strikes, it’s tempting to cut back on watering of established trees or stop watering altogether. And maybe water restrictions in your area force your hand. I hate to see it happen, because trees can offer many benefits – most notably shade for homes to cut down on energy use, and shade for other plants to keep them alive and in need of less water. Of course, you can’t beat the enjoyment of sitting under the shade of your favorite tree. I won’t even get into how depressing it is to see dying trees in front lawns…

Ideally, your lawn has only native trees, and especially xeric varieties. In that case, the trees adapt to conditions more easily. Some survive on rainwater alone, but most need a deep watering about once a month during the heat of summer.

desert willow tree xeric
The desert willow (Chilopsis linearis) is a perfect xeric tree for warm to hot desert climates. This one is from a Tucson, Arix., garden.

To water your a mature tree that requires irrigation, avoid a common mistake — watering only near the trunk. Trees do not have tap roots, but instead have a root system that extends out from the tree, more or less mirroring and extending just past, the tree’s branches above. So, when you set out your hose or set up a drip or soaker system, begin near the trunk, and then work your way out to the edges of the tree’s canopy. Scroll down in this handout on caring for trees from Colorado State University for a photo of a soaker hose layout.

To water deeply, you have to water slowly. That means setting your hose or irrigation system to deliver the water at a lower rate for a longer period of time. To reach the roots, the water needs to penetrate the ground to at least 12 inches. If you’ve ever seen roots growing at ground level, they’re probably doing so because the tree is receiving too little or too shallow watering.

Don’t dig a hole around the tree to help get water to go down deeper. The hole allows air in and dries out roots!

If possible, avoid using a sprinkler to water trees. In addition to producing shallower roots, the sprinkler wastes water by dispersing it into the air, where it evaporates. And some trees are subject to leaf diseases from constant watering. The only time I ever spray a tree or bush is if it has aphids, and I give it a fine-water spray in early morning to wash the aphids off.

If you can’t reach a tree with your hose, you can drill a few holes in a 5-gallon bucket and carry it out to your tree. The water will flow more slowly through the hole than if you pour the water on the ground. Move the bucket out and around the tree’s base with each refill.

apple tree along river.
This apple tree is hard to reach with the hose, but we don’t water it because it is along the river bank and the roots take up plenty of water. This year, it had twice as many blooms and may give us some fruit. Trees can help preserve water sheds.

If you want to save tap or well water, reuse! Direct roof water to a tree using the downspout and a dry river bed. Save shower water in 5-gallon buckets (with no holes – you have to get them outside!) but only use the water that flows while the shower warms up, not any soapy flow.

If you have other clear water to dispose, such as kid or dog pools, empty the water onto tree roots instead of a random place in the yard.

Another Reason to Plant Natives: No Soil Amendment Needed

Where I live in New Mexico, the soil is more alkaline than acidic. That means I might as well forget ever trying to grow blueberries, but asparagus is a great choice. We even found some old or wild stalks along our ditch bank last year.

And a soil’s pH balance is just one consideration. Soil texture and drainage are especially important to a plant’s success in a vegetable, herb or ornamental garden. If we didn’t add some organic matter to our vegetable garden each year, the soil would compact from foot traffic and lose nutrients from its work feeding plants. So each year, we work the soil with mushroom compost to keep it rich, water absorbent and well draining.

amended soil for vegetables and herbs
This is part of our ornamental garden, amended with organic matter to grow edibles this year.

Native plants

I couldn’t – and wouldn’t – rework my ornamental garden soil each year. For one, it would be nuts to dig up perennial plants! So gardeners often are advised to add a little bit of compost to the hole dug for a new tree, bush or flowering plant. The compost enriches the soil around the roots, and as long as you water as suggested in the first year or so of more rapid growth and root set, the plant should thrive. But what happens as the plant grows beyond your amendment, especially if you put in a rapidly growing shrub or tree? Eventually, the roots work their way into the soil you haven’t amended. If the soil is so poor or compacted that the roots can’t break through or thrive, the plant could be stressed at the least.

If you choose a native plant, especially for a xeric garden, it’s likely that you won’t have to amend the soil at all. A plant that is adapted to your area’s typical soil makeup will do better if you just loosen the soil around it, usually to an area at least three times larger than the root ball. No need to add anything.

chocolate flower in New Mexico rock garden
The chocolate flower (Berlandiera lyrata) is a native to our region. It crops up from seed around our garden and lawn. And yes, the blooms smell like chocolate! That’s a rosemary in the right foreground.

If plant instructions, or one article or expert tell you to add to the soil, it helps to verify the information with another source. That’s especially true if installing a native plant in your xeric garden. And it’s even truer depending on the first source of advice. There are plenty of reputable sources, and then there are myths, many of which can be perpetuated by those who stand to profit.

lavender in rocky soil
We placed several lavender plants in one of our beds, and maybe should have tested the soil first. Lavender is native to the Mediterranean, where the soil is rocky and alkaline. So it grows well here, but this soil had compacted more than we realized.That and some some cool, wet weather gave our plants a rocky start! Lesson learned.

When amending

It’s also good to check local sources when amending soil. For example, you might hear that adding sand improves drainage, but if you add too little sand, or add sand to clay soil, you can make matters worse, and your soil sets up like concrete. Oh, those poor plant roots…

Most organic matter is good for soil, but plenty of myths abound there as well. For example, manure needs to cook down or compost with brown materials before throwing it on your vegetables. Wood ash is often touted as an amendment, but not in New Mexico, where the soil already is alkaline. Wood ashes also are high in salt. I talked about Epsom salts in a previous post. The bottom line? Get local advice from a few good sources, and if you go with native xeric selections, you probably won’t have to amend the soil unless you have a severely compacted or poorly draining area.

 

Use Plant Finders and Identifiers to Plan Your Xeric Garden

So you want to plan a xeric garden, or begin converting your garden to a low-water design. It can seem overwhelming at first. You can call in a xeric landscaping professional, especially for a big job. But to make small changes, you mostly need help finding good replacements. For example, what’s a low-water plant with red blooms that enjoys a mix of sun and shade?

Enter a plant finder. Most let you select any number of fields or filters, and many also provide searches in both common and botanical names.

deep red iris bloom
OK, so we all know this is an iris. That’s all I know so far, because it bloomed for the first time a week ago. I just had to include a photo of it in some post.

Plant identification tools also help, but I find they work best if they have several photos – at least one close-up shot of foliage and flowers, and another full shot of the plant. You’ll use identification often if you pay attention to plants as you drive around your town or neighborhood, or spot a great specimen in a friend’s lawn. Your friend may have no idea of the plant’s name. Here is a short list of plant ID and plant finder sources:

Identify Plants Online

One of my favorite Southwest sources for xeric and high-desert selections just added a plant finder. Plant Select provides a dozen fields, including water needs and deer resistance, important considerations for me.

plant Select plant finder
Screen shot of the Plant Select plant finder. It’s got plenty of filters to help you plan your xeric garden.

The National Gardening Association also includes an extensive plant finder on its site, which lets you select USDA zone.

Finally, for a more scientific approach, go to the USDA site. I’ve had more luck there with the scientific name, but that’s pretty easy to find with a good online search of a plant’s common name.

Plant Identification Apps

I love plant ID apps, because I always have my phone with me in the garden. The problem is tracking down good one with Southwest plants. So far, the only one I’ve found that’s free, dedicated to xeriscaping and accurate for my area is SW Plants. It’s from New Mexico State University. If anyone out there knows of a better one for xeriscaping, I welcome input!

SW plants plant finder
SW Plants app on my phone. The search works well for the 750 xeric plants included.

 

SW plants app zinnia photo
The photos in the SW Plants app are pretty nice, but small on my phone.

In addition, Audubon has apps for wildflowers and trees. Otherwise, as in most cases, content comes from and focuses on the northeastern and southeastern portions of the country…

Remember Books?

We have some gardening books. In fact, a shelf of our sitting room is lined with them. And I often can identify a plant by consulting several of them. Sure, sometimes a Google search is quicker, but it’s too hard to rely on images posted by people using common names to identify a plant. So it might be a good place to start, but books local to your area are best. My favorites for this area are the Sunset Western Garden Book (keeping in mind that Sunset assigns its own zones) and Judith Philips’ New Mexico Gardener’s Guide. Any book on native plants and wildflowers for your state or region is priceless as well.

shelf of gardening books
Got gardening books? Many books have older, dull photos or illustrations, so check out photos before buying.

Keep Current Catalogs

Catalogs are excellent resources, especially for planning your garden each year! We save a few of the most recent from our favorite suppliers, and often can either identify a plant we already have or see somewhere nearby, or plan our garden each spring with the catalog’s help. They have the best photos, if you’re willing to spend time leafing through pages. It’s one of our favorite activities with coffee on spring mornings!

I recently helped a friend identify a gorgeous wildflower she spotted on a hike in Los Alamos, using a combination of our catalog from Plants of the Southwest and an online search. Our other favorite catalog arrives regularly from High Country Gardens.

Favorite Xeric Plant: Penstemon

The hummingbirds are swooping around the garden, and soon they will enjoy feeding off several water-wise Penstemon species. The penstemon, also called beardtongue, is a versatile low-water native plant in New Mexico and the Southwest.

In fact, penstemon does best with no added water at all. And the plants can thrive in full sun or light shade. Penstemon comes in a variety of sizes, shapes and bloom colors. But they have in common a slender trumpet-shaped flower that hummingbirds love.

purple penstemon
Hummingbirds love penstemon flowers, but can you also spot the bees in this photo?

Caring for penstemon

Penstemons usually prefer somewhat sandy or clay soil, and don’t need added compost. Most species of penstemon are perennial in our zone (6 to 7), but some are annuals. They’ll bloom from summer to frost. Species such as Arabesque Red bloom from summer through first frost with deadheading. However, if you leave some blooms on the plant, the seedheads ripen and break, which causes the plants to reseed. We’ve had several volunteers come up in our rock garden. And birds love the seeds!

red penstemon AAS regional winner
Arabesque Red was the regional winner (including the Mountain and Southwest regions) fof the All-America Selections in 2014. Photo courtesy of the National Garden Bureau, Inc.

The only way to really harm penstemon is to overwater or overnourish this easy-care plant. Use fine gravel for mulch. Occasionally, aphids gather on the stems, but you can use a fine mist of water to spray them off in the morning and check a few days later.

Penstemon can work well in containers, especially if you select a lower-growing variety. Select low-water companion plants, so that the penstemon does not receive too much water. If it does, it can become leggy. You might find that a penstemon in a clay pot needs occasional watering compared with one in your landscape.

In a xeric landscape

Penstemons are great plants for xeric landscapes. Low growers such as Desert beardtongue (P. pseudospectabilis) spread to about 15 inches wide and 30 inches high, with purple-maroon flowers on stalks above the blue-green foliage. The pineleaf penstemon (P. pinifolius) is a native wildflower with tiny needle-like leaves and bright orange-scarlet flowers. I love watching the hummingbirds maneuver effortlessly into the flowers.

pineleaf penstemon
Our pineleaf penstemon hasn’t flowered yet, but it’s still attractive, with the pine-like foliage and its low spreading nature.

A taller, lankier type such as Rocky Mountain beardtongue (P. strictus) looks gorgeous against a fence, wall or tall rock. Its purple flowers contrast nicely with yellow or white bloomers in the foreground. The bushier pineleaf or Desert beardtongues are perfect to tuck in a corner, or along a step or walkway.

desert beardtongue penstemon
The Desert Beardtongue is a 2015 Plant Select winner. Photo by Bill Adams and courtesy of Plant Select.

No matter which variety of penstemon you choose, you’ll be rewarded by hummingbird guests and the beautiful blooms that appear with very little care on your part!

Plan a Xeric Turf Lawn

Because the drought in California is so severe and restrictions attempted earlier this year did not have much effect, regulators adopted unprecedented restrictions at the urging of Governor Jerry Brown that include encouraging homeowners to let their lawns die. A survey of the state’s local water departments showed that water use fell less than 4 percent in March of this year compared with March 2013; total water use has gone down only about 9 percent since summer 2014. The new regulations require cities to cut use by up to 36 percent.

What remains to be seen is how cities will enforce the laws, or help homeowners do a better job of conserving water.

all-gravel lawn
This is the choice of most homeowners who xeriscape, and now the only choice in drought-stricken California. Note the bermuda grass creeping back through the gravel.

Some of the crisis could have been avoided with xeriscaping years ago. Californians and any of us in arid Southwestern climates do not have to  give up on turf lawns completely, at least if we act before a crisis of California proportion hits. You can responsibly incorporate some turf into your xeric landscape rather than going all gravel. Let me first explain the benefits of keeping a limited amount of turf.

  • As I’ve mentioned before, xeriscaping includes zones, and the zone closest to your home is called the mini-oasis. This is where you should plant turf and your highest water users, keeping “highest water users” relative in scope and quantity. One reason is that you can water some of the plants in this area with rainfall runoff from the roofline and downspouts. And when in a drought, you should catch as much rain as possible.
  • The other reason to have some planting and green around your home is to help keep your house cool in summer. This might not be as important if you live in the mountains (although if you do, I bet you are like us, and rely on cross-breezes and cool evenings instead of air conditioning!). If you switch to all gravel instead of some grass or native plants, your house will become hotter, and eventually you’ll use more energy to cool your home. If you have evaporative cooling, guess what? You’ll use more water, too.
  • Any trees planted near the house that help shade it in summer will likely die if you cover their roots with plastic and rocks.

I’m not saying you should sod a huge lawn or use any grass you like, however. Many people in Albuquerque, where average rainfall is 12 inches a year, have planted lawns made up of a Kentucky Bluegrass mix. Those lawns need about 40 inches of rain a year, and I don’t have to tell you that Kentucky is hardly a desert…

So, what’s the ideal situation? Plant a small area of native, low-water grass near your home (especially on the south or west sides) or around the base of the tree that shades your house. Native grasses have adapted to live in their environment, and should thrive in your climate with little to no supplemental watering. Here are a few examples of sod-forming grasses:

  • Blue grama (Boutleoua gracilis). Blue grama is best known for its seed heads, which form in middle to late summer, assuming you stop mowing for a bit and let them go to seed. The low-water, warm-season grass has fine green blades and loves hot weather. It will winter over in cold climates as well.

    Dried grama grass seed heads
    We mowed around this clump of blue grama for weeks last summer and fall to let it go to seed and hopefully spread. This is how it looks in early spring.
  • Buffalograss (Buchloe dactyloides). Buffalograss is a native prairie grass that establishes quickly from seed or starter plugs. It won’t work as well under a tree or the shade of a house as some natives because it prefers full sun. But the warm-season grass requires little mowing and only two inches of water a month, even in the hot summer.
  • Western wheatgrass (Pascopyrum smitthi). This cool-season grass works in most soil types and uses little water. It has bluish leaves and spreads by rhizomes, so be careful where you plant it. Also, the grass is native to high elevations.
winter wheatgrass
Winter wheatgrass in a New Mexico horse pasture.

You also can mix buffalograss and blue grama for a native lawn that fills in quickly and densely.

blue grama grass in spring
This is some blue grama grass near the clump that went to seed. It’s greening up nicely in early May with only rain water and some fertilizer from deer.

Avoid planting turf on a slope, and keep your small lawn area away from sidewalks or curbs, so that when rain or the occasional sprinkler water hits the grass, the moisture stays there and doesn’t run off.

Finally, with native grasses, you have to learn to go with the flow, so to speak, and not expect to have the greenest, most dandelion-free lawn on the block. The lawn’s health will vary from one year to the next. We have several acres of various native grasses and even more weeds. Obviously, we do not water any of the lawn/pasture. It’s completely up to Mother Nature. We control the weeds in some areas and mow when it all begins to grow in late spring or early summer.

salinas-pueblo-missions-natural-grasslands
Natural grasslands at Salinas Pueblo Missions, a national park near Mountainair, N.M. I am certain this grass receives no irrigation.