Planting Season

Ed inspects the first delivery of annuals in mid May.

Ed inspects the first delivery of annuals in mid May.

May Day at tea time.

May Day at tea time.

We were wise to wait until after Mother’s Day to start planting annuals. Nights have remained cool. The soil was downright chilly. Soil temperatures regulate much of the activity above ground, and when they started to warm, our fair city greened in a hurry. It’s hard to believe that six short weeks ago, work was called on account of snow.

Although we have nearly finished planting annuals for the season, the carport and back patio are once again filling. This time it’s with perennials. We have projects ranging from converting an artificial turf putting green destroyed in the Waldo Canyon Fire to establishing groundcovers under a lofty canopy to planting up beds created in response to water shortages in an effort to reduce thirsty turf.

The old putting green about to receive its first plants.

The old putting green about to receive its first plants.

Planting season will continue through June, as long as daytime temperatures stay reasonably normal (no triple digits, please), and evenings cool. The one condition: Homeowners must take responsibility for regular hand watering to get plants established. To be within the rules of current water restrictions, any watering that takes place outside of your designated hours and days must be done with a drip system or by hose with a positive shut-off and on trees, shrubs, and beds only.

If too much heat comes into the forecast, we’ll take a break in planting. It really isn’t wise to ask plants to deal with getting situated in a new location during a hot spell. Too much stress. Don’t believe me? Try it yourself: Move to a house without air conditioning in, say, Houston in July. Doesn’t sound the least bit appealing, does it?

When It’s Too Darned Hot: Tasty Soil, Tender Mulch, and Just Enough Water

Have you felt yourself wilting, lately?

A day in the nineties or triple digits, makes me glad I’m a mobile creature. I can retreat to the shade or the relative cool of an interior. But what happens to plants when the temperatures soar?

Plants, like people, differ in their responses to heat.

As you can imagine, plants which evolved in steamy tropical rain forests and searing deserts survive the heat without much apparent fuss. It’s the plants from temperate zones which stress and cause the gardener to stress even more.

Like afternoon naps for the gardener, one of plants’ heat survival strategies is dormancy. A great example is the natural response of bluegrass varieties. When the heat turns up, bluegrass turns brown and goes to sleep. The water we pour on it through the hottest months isn’t so much to keep it alive, but to keep it cool. As long as irrigation water is evaporating and cooling the lawn, it stays relatively green. According to University of Colorado Extension, a healthy bluegrass lawn can get by on twice weekly irrigation and can survive in dormancy for weeks or even months without irrigation. Once cooler temperatures return, begin regular watering, and the green will follow.

Many flowering annuals take a break in the heat. While they aren’t totally dormant, they save their energy for the opening and closing of stomata, a kind of pore on the undersides of leaves. Perennials that normally bloom in summer’s heat, such as lilies, may wrap up their season in a hurry. When a plant wants to rest from the heat, it’s important to refrain from fertilizing. This is especially true of roses.

The Golden Jubilee Agastache pictured above is in a serious heat wilt. It is also more sensitive to soil moisture than many of the plants around it. I call it a signal plant. When it droops, I watch it as the evening cools. If it perks up, soil moisture is not yet an issue. If it doesn’t, you’ll see a sprinkler out in the morning.

During a heatwave, the natural impulse of many a gardener is to turn on the tap. While it’s important to keep garden soils from drying completely, we often water more frequently than necessary. In sandy, porous soils, three times a week might suffice. In clay-based soils, twice a week could do it. The trick is to irrigate for longer periods during extreme heat, making sure moisture penetrates to a depth of 6-8 inches.

To muddy the waters a bit: All watering rules are relative. How quickly do the temperatures rise in the morning? How far did they go down overnight? What is the relative humidity? Has it been windy? Any of these factors can change your watering regimen.

Knowing when to water is told by the soil. Put a blade in to a depth of 3-4 inches and make an opening. Feel the soil at the bottom of the opening. If it is cool and damp, all is more or less well. If it is dry, it’s time to water. Relying on plants to tell you when to water can be misleading. While it’s true that plants droop when they need a drink, they also droop in heat. They can also droop from drowning.

The same principles apply to the vegetable garden. According to University of Colorado Extension, a properly prepared veg garden should be able to tolerate intervals of 2-7 days between watering.

These watering intervals might seem counterintuitive at best, preposterous at worse, but the key is to follow other practices as well.

The foundation to any lawn or garden survival through these conditions is living soil. Soils that are properly amended save on water and support stronger, more resistant plants.

In addition, the use of mulch is crucial, even in the veg garden. The goal should be no exposed soil surface. Even half an inch of humus, leaves, straw, or fine gravel will shade the soil, helping to keep it cool and reduce evaporation.

Timing and delivery methods of watering are also important. Most experts agree: water in the morning and deliver the water at the soil’s surface, under the mulch, if possible. This helps mitigate fungal and disease issues as well as conserve water.

Keeping up with watering is sometimes the only thing a hose-dragger like me can accomplish during the hottest weeks. The comfort is knowing that as the day’s grow shorter, longer nights and cooler overnight temperatures give both gardens and gardeners a much needed respite.

Movie Review: Dirt! The Movie

Sometimes, even the wildest gardener needs a reminder: soil is life and life is soil.

Growing up in Iowa, about 80 miles from the mighty Mississippi, I took soil for granted. What did I know? It was deep. It was black. Stuff grew in it.

Apparently, I was in good company when it came to paying no special heed to dirt. Sometime just past the middle of the last century, the first “green revolution” swept through the country. Petrochemical fertilizer replaced cow poo on Iowa’s fields. So?

Well, the soil became depleted and started to die. So?

With enough fertlizer and water, food crops will grow in the thin soils of the desert. Why should I care if the dirt in Iowa dies?

Decades later, the answer to that question is getting around.

Dirt! The Movie is a kaleidoscopic documentary that plays on the heart like a romance.

The opening scenes, introducing us to the impressive line-up of soil experts and activists, are full of beauty, humor, and whimsy. Children in India dance in the dirt, throwing it in the air with glee. A wine officianado cups a precious handful and dabs his tongue in it. We meet earthworms and mushrooms. It’s a dizzying, giddy love-fest.

Then, kaboom! Scene upon scene of dirt in trouble, dirt defiled, dirt imprisoned beneath concrete. We are warned: throughout history, human civilizations rose and fell in accordance with how they treated dirt.

Thank goodness, this is not where the movie ends. The closing scenes give us hopeful examples of people of many stripes entering a mutually healing relationship with soil.

Only 80 minutes long, visually stunning, and appealing to both our practical and visionary drives, I highly recommend it.

To Build or Not to Build

Say you live in England and you love desert plants, succulents and cacti from South Africa, Baja California, or somewhere really exotic, like Colorado? Your soil is constantly moist, lightly acidic, crumbly with leaf-mould. It’s terrible! What can you do?

That’s right, you’ll have to build your own soil. Make it lean. Make it gritty. Make it quick to drain. Use a little of your garden soil and mix it with equal parts coarse sand and lightweight perlite. That should do it.

A handmade cactus garden.

Now, isolate the stuff in a pot so you can control how much water it doesn’t get, and so it will dry out fast, like it would in the desert. Then plant it up. Put the whole kit and kaboodle someplace in full sun, but sheltered from the rain, and you’ve got it. Instant, handmade desert.

Sound like a lot of trouble?

It is.

It’s the same kind of trouble we semi-arid plains dwellers go through to grow broccoli.

But what if we semi-arid plains dwellers want to grow native yucca, shrubs, sage, cactus, agave, grasses, and wild beardtongues? Should we build the soil?

It’s a great question, and one with no definitive answer.

Gardeners have a hard time resisting compost or believing (at least at first) that anything of value can grow without our TLC. There’s always the thought that a little assistance can’t hurt. Isn’t it what every plant hopes for?

Maybe. Maybe not. Conventional ideas of fertility may not be a great thing for plants that evolved in and for such “poor” soils as ours. There is even research suggesting native plants will form stronger myccorhizal communities, taking up greater quanities of nutrient from mineral-rich soil, if left to their own devices.

However, there are gardens featuring native plants throughout Colorado, in which soils were amended before the plants went in. There is no question these gardens are thriving.

Native rabbit brush, yucca and grasses, connecting the cultivated with the wild.

To build or not to build?

Why not join in the great experiment yourself, and try some natives?

Life Beneath Our Feet

In addition to dirty knees and fingernails, gardeners have soil on the brain.

In the Pikes Peak Region of east central Colorado, a layer of recognizable top soil is generally thin, if it exists at all. Even so, the undisturbed landscape is far from barren. A host of different plant communities have adapted to a wide variety of growing conditions, not the least of which is the soil beneath their feet.

Our native soils tend to be mineral rich and poor in organic matter. Wind, the great eroder, ice, the occasional stream, and other natural forces break stone into ever smaller particles. Depending on the parent stone, the results are gravel, sand, clay, or silt. Low humidity, high winds, and gully-washing rains contribute to the mobility of these particles.

Native plant community in northern El Paso County.

Native plants adapted to the soil and atmospheric conditions by developing root systems that could hold tight, exploit the minerals, and take up scant moisture. They adapted above ground by forming leathery or hairy or pale green leaves. They spread themselves around via windblown seeds or passage through the guts of birds and mammals.

The tough nature of the leaves combines with low humidity and high winds to keep fallen organic matter from staying put and breaking down into humus.

Thus, existing soil, atmosphere, and native plants form a self-sustaining system.

Enter the wily human, many of whom are never quite satisfied with things as they are, and, let’s face it, we’re not at all suited to nibbling on sideoats gramma, yucca (except the flowers), or mountain mahogany. To encourage nearly every plant that isn’t native to the area, gardeners have to make changes. Many think it’s just a matter of supplementing the moisture that does (and just as often doesn’t) fall from the sky. But the issue is deeper.

Shade trees, blue grass, most ornamental flowers, and nearly all of our favorite vegetables evolved or were developed in areas where soil and atmosphere have vastly different characteristics from our own. Below the surface, mycorrhizae form a link between soil and plant root, converting soil into nutrient for the plant. There are thousands of different mycorrhizae, and more is being learned about them all the time. What is known: the microorganisms, the plants, and the soil have become what they are together in fairly specific ways.

It comes as a surprise to many to learn that soil, even the sparse grit and heavy clays of the Pike Peak Region, are teaming with life. It may also come as surprise that the partnership of soil and plant communities is very easily disturbed or destroyed and not so easily restored. Scraping the surface of vast tracts of land to make way for houses and lawns, even repeated foot or bike traffic interfere with or remove entirely what took a very long time to create.

Over the next weeks, look for more posts about what gardeners can do to build and maintain healthy soil-plant relationships.