About Nitrogen

NITROGEN KILLED THEM. All those poor dogs and cats that died recently from eating contaminated pet food--they died because of nitrogen. Not directly, of course. But because of a desire to increase the amount of nitrogen in dog and cat food. That was the reason that makers of pet-food ingredients in Asia added melamine, an inexpensive synthetic compound that happens to contain a lot of nitrogen, to their product. And that in turn was the contaminant that killed all those pets recently.

A column by science writer Natalie Angier in today's New York Times got me thinking about this connection, which is very relevant to us as gardeners because we use a lot of nitrogen. Nitrogen is the N in the N-P-K that adorns every bag of fertilizer we buy, whether synthetic or natural, denoting the presence of three nutrients that are vital for healthy plant growth.

As Angier explains, nitrogen is also vital to animal life, an essential building block of the proteins from which we animals are made. Nitrogen and protein are so closely linked that a quick way to test a product for protein content is to test for the presence of nitrogen. Unfortunately, it's possible to cheat on this test, boosting nitrogen content by adding an inexpensive high-nitrogen compound instead of a (more expensive) protein. That's what happened to the dogs and cats: The Asian makers of pet-food ingredients added melamine so that their products would test out as having a higher protein content than they really did.

Although nitrogen is common in the air, it cannot be used in this form by animals or even by most plants. To be useful for life, nitrogen must be fixed, another term familiar to most gardeners. Most of us are aware that certain plants, especially those in the legume family, are capable of converting nitrogen to usable form. This is why it's a good idea to plant beans (nitrogen-fixing legumes) next to your tomatoes (heavy users of nitrogen that can't fix the stuff for themselves). Another nitrogen source most gardeners know well is animal waste. (I don't know about you, but I did not know--until Angier told me--that rain falling on a garden after a thunderstorm also contains a lot of usable nitrogen, which has been fixed by the electricity in lightning.)

Most of us also know that nitrogen must be used sparingly in the garden. Too much nitrogen, and plants turn black and "burn." That's why we're careful about how much artificial fertilizer we use, if we use it at all, and why natural fertilizers such as composted manure are much safer (and better in a number of other ways) to use. Even fresh manure can be too "hot" for the garden.

Many of us even realize that nitrogen can cause problems when it reaches waterways: Dangerous algal "blooms" are often caused because runoff containing fertilizer, leaks from sewage systems, or animal waste increase the amount of nitrogen and other nutrients in a body of water, feeding the algae in the water. That's another reason why it's such a good idea to use fertilizers, such as composted manure, that do not have a super-high nutrient content and will release their ingredients slowly rather than all at once.

Less well known is that some non-leguminous native plants are nitrogen fixing. Alders, for example, are widely thought of as weeds because they readily spring up on abandoned farmland, in clearcuts, and any other land that has been harshly treated by humans. At one time it was customary to cut them down or treat them with herbicides as quickly as possible. Then in 1990, research conducted on a plantation on Vancouver Island in Canada found that Douglas fir trees grew two and a half times better when they were grown together with the locally native alder. The alders were adding nitrogen to the soil, and this in turn was encouraging the growth of surrounding trees. More than 15 years later, people who (like me) are trying to restore large tracts of land often look forward to the arrival of alder, seeing this as the first step in a natural process of ecological restoration.

The relationship between alder and other plants is an example of Nature's wisdom: A plant that can thrive on harshly treated soil also has the ability to improve that soil, making it ready for other plants. The more we learn about Nature, the more we discover that all sorts of plants and animals human beings disparage actually have important roles to play. The fact that our first impulse was to cut the alders down is an example of why humans should pay more attention to the lessons Nature has to teach. The fact that we didn't even begin to understand this simple relationship until 1990 shows us how much we have left to learn.

What does all this mean for the gardener?

I think one lesson Nature is teaching us is that more is not better. In our gardens, this lesson should lead us to avoid solutions that may seem quick and easy at first, such as using potent artificial fertilizers, in favor of slower acting, more natural solutions that may not give overnight results but will work far better and will do far less harm in the long term. As my mother always used to tell me, "Slow and steady wins the race."

Another lesson is that we need to trustNature a lot more than we are inclined to: If alders tend to grow on badly treated soil, for instance, we need not jump to the conclusion that Nature has made a mistake. On the contrary, the best response is usually to be patient, to give Nature the benefit of the doubt, to try to learn more about what she is up to, and to try to work with Nature rather than against her.

Mother (both of them) knows best.

Good Drainage for Good Planting

MANY PLANTS DIE HORRIBLY if their feet are wet. If your site is mostly wet, as mine is, you can address this easily by planting the species--typically those that grow on or near wetlands--that will tolerate wet soil. You can get a lovely garden this way; in fact I find that I'm designing more and more of my garden in such a way as to accommodate wetland plants.

But if there are "dry feet" plants you can't live without, the only solutions are either raised beds or a rockery (which is really a type of raised bed). By elevating your planting surface above the soil's natural level, you ensure that water will drain away from plant roots. If you're a cold-climate gardener, an additional benefit is that the soil in a raised bed generally warms up faster than does the natural soil.

Many plants love this type of environment. Most vegetables and culinary herbs require it, as do many beautiful plants that are native to North America, such as purple coneflower. Many of the best butterfly plants are dry-footers; if you want a butterfly garden, I definitely suggest finding or making a sunny, well-drained spot for it.

A conventional way to make a raised bed is to build one out of lumber, but lumber costs money, might be treated with toxic chemicals, and may not have been harvested sustainably.

Fortunately, there are easier ways to make raised beds. For instance, for my butterfly garden here in the Northeast, I was able to take advantage of regrading work that had to be done anyway. When I got here, the basement flooded regularly. A local backhoe expert fixed that for me by changing the drainage pattern in my front yard, and in the process he piled dirt in front of my house. The photo to the left shows the work being done in August 2003. I mixed manure into the soil and planted in 2004, and the photo above shows my butterfly/hummingbird garden in bloom in June 2006. Plants such as salvias, penstemons, and dianthus are thriving in the sun and good drainage. (Reflected sun from the white house helps to make this spot even warmer than it might otherwise be, while the house itself helps to shelter the site from wind. This is a perfect spot for a butterfly garden.) An added advantage of this bed is that, because it's sloped, the plants are more visible than they otherwise might be.

But I don't want to give the impression that you need a backhoe to make a raised bed! The point of this example is that you can take advantage of almost anything that happens on your property, even mini-disasters like flooding in the basement, to make good planting sites. Lemons into lemonade and all that.

The photo below shows a raised bed I made for my garden in the Pacific Northwest. This property had a long gravel driveway that I didn't particularly care for. I also had a lot of yard waste that could have been turned over to the county for composting--but why give away all those good nutrients? So I piled the yard waste on the driveway, let it sit until it had compacted a bit, added some good-quality dirt, and planted the mound with dry-feet plants such as artemesias and sedums. The logs that define the edges of this mound were an afterthought, inspired by a raised bed my friend Brett Johnson made out of some unwanted firewood. An arborist I knew offered me the pieces of an alder he'd cut down, and I grabbed 'em.

Some sort of edging definitely makes a raised bed look tidier. I use whatever I have handy--logs, rocks, even bits of broken concrete. But edging isn't absolutely necessary. For utilitarian purposes, such as a vegetable garden, a simple mound of soil will work remarkably well. The photo below shows one of my vegetable beds in the process of being made by mounding up soil I purchased by the truckload from a local composting facility. Thanks to these beds, I am generally able to start planting and harvesting earlier than my neighbors who have not adopted the raised-bed strategy. By using soil that had been mixed by professionals specifically for vegetable gardening, I was also able to get a good harvest my first year, without having to spend several years building soil.

My Forlorn Front Yard 4 (Improving Soil, Simply)

POOR AS IT IS, MY SOIL SITUATION IS COMMON. People who follow all the popular lawn-care recommendations are a lot more rare than lawn-care advertising might lead you to think--the homeowner whose idea of lawn care is to mow every week or so is blessedly commonplace. I say blessedly because, on the whole, less lawn care is far better for the environment. So I'm always happy to say hello to a neglected lawn.

But soil suffers when you run a mower back and forth over it year after year. If you rake up the cut grass and remove it, you also deprive the soil of nutrients. The result can be what I found when I moved into this house: compacted, nutrient-poor soil in which the healthiest plants are the weeds, especially the dandelions. Because of their long, strong taproots, dandelions can break up compacted soil and fetch nutrients to the surface from well below ground. Homeowners are supposed to regard dandelions as an enemy. Yet ironically, many lawns remain healthy largely because they do contain so many dandelions.

What to do if, like me, you want to replace that lawn with native plantings? Some people recommend an approach in which you till the soil, add amendments if you consider them necessary, water well to encourage weed seeds to sprout, then till again. This process must be repeated until all weed seeds have been brought to the surface, have sprouted, and have been tilled back into the soil. Only then can the soil be planted.

There are a lot of disadvantages to the till/water/till again approach: Tilling around trees can injure the roots, killing the trees. Tilling destroys any soil structure you already have. With this approach, you usually have to hold off planting for at least a year, as it takes at least that long to bring all the weed seeds to the surface and force them to sprout. Tilling requires extensive use of an internal combustion engine, which burns fossil fuels and is polluting. And finally, this approach is a lot of work!

Here's my much simpler, easier approach:

1. Collect a lot of cardboard. Big pieces are better. Heavy cardboard is best. The cartons that refrigerators and other big appliances come in are ideal. Appliance stores will often give them to you for free.
2. Order a big load of topsoil or compost. I usually order about 14 yards at a time, which makes a mound the size of a small car. That seems to be the outside limit of how much dirt I can move around in one season.
3. Put the cardboard down on the ground. Be sure to overlap the edges so that every bit of ground is covered.
4. Cover the cardboard with the dirt. Don't put down less than an inch or more than 4 inches; anything more than 4 inches can suffocate the roots of trees, which will kill them. (A few species of trees, such as Deodar Cedar, seem to be sensitive to even that much disturbance around the root zone. If you have a tree you're especially concerned about, consult an arborist.) However, try to spread the compost as deeply as you can up to that 4-inch limit.
5. Plant the compost densely with a variety of inexpensive, low-growing native plants. I'll talk more about this the next time I post an entry in this series. Meanwhile, please note that, with this method, you can--and in fact should--begin planting right away.
6. Water well. The cardboard under the compost will start to soften and disintegrate as soon as it's soaked. You can then put a spade through it and immediately plant any trees or shrubs you have planned for the space.
7. Keep watering as necessary for the first few years. Once established, native plants don't usually need to be watered, but you do have to water them until they have established their roots.
8. Weed occasionally. The cardboard and compost will smother most weeds. Because this approach buries weed seeds, you do not add to your weed problem by bringing weed seeds to the surface as tilling does. But some weeds always manage to punch through even the heaviest cardboard and thickest layer of mulch. Others blow in as seed, taking root in the compost. So occasional weeding will be necessary. I'll talk more about that in a later post.
9. Relax and let nature do the rest of the work for you. That top layer of rich earth will soon attract earthworms; they'll eat their way up, feed, breed, and eat their way back down again. This eventually mixes the compost into the rest of your soil just as thoroughly, and far more gently, than tilling would have. Also, the more earthworms you have, the more earthworm castings you get--and earthworm castings, as everyone knows, are great for your soil.

Although this approach is, sadly, not work-free, it is far easier than any other method I'm familiar with for improving compacted, nutrient-poor soil.

Alternatives to Peat

MY FAVORITE GARDEN BLOGGER has been writing about peat. A lot of people are raising questions about the environmental cost of using peat, which is taken from bogs and wetlands. Blogger Jodi DeLong, aka Bloomingwriter, is a thoughtful, concerned gardener (to say nothing of a charming and knowledgeable writer) who, in addition to all the other useful information she dispenses, takes the time to ponder questions such as this one.

On reading Jodi's blog, my first thought was to offer an alternative to peat. Fortunately, I know about a mulch/soil amendment formula that is so good I doubt anyone who uses it will ever want to give peat another thought. I got the recipe from Anne Lovejoy, a garden writer who lives in Seattle and is very popular on the West Coast:

*composted manure + dried alfalfa*

If you can’t get the dried alfalfa from a garden-supply company, blocks of dried alfalfa (aka 'alfalfa pellets') are sold as goat feed in small sizes or horse feed in large sizes; the smaller size works better if you can get it. If you buy alfalfa as animal feed, you have to be sure that it hasn’t been medicated, however.

When it gets wet, the dried alfalfa swells and forms the best weed barrier you've ever seen. This combination also feeds the plants. Lovejoy says, “When combined, manure-based compost and alfalfa synergistically release extra nitrogen to plants, which benefit them both quickly and over time.” I mostly know that I'm in love with this stuff. It's much easier to put down than peat is; as far as I know, the nutrient value is much higher. And it rewets readily, which peat does not.

Now, I have always remembered the recipe as calling for equal parts of the two ingredients. I've gotten excellent results just by putting down a scoopful of manure followed by the same amount of alfalfa, and so on. However, Lovejoy gave a more complicated explanation in a recent Seattle Post-Intelligencer column I found on the Internet. Personally, I plan to stick with my easy version: one scoop manure, one scoop alfalfa pellets, repeat.

What about peat? One of the advantages of being primarily a native plant gardener is that I don't usually have to worry about questions like this. Generally speaking, native plants are adapted to native soils. Sometimes I have to make changes to soil that has been badly treated (compacted, for instance) in the past, but the changes are generally minimal. I usually start a native garden by putting down cardboard topped by compost. This kills any grass and attracts various critters (worms, burrowing animals) who will break up compacted soil. After that, however, a native garden is supposed to take care of itself. Most of the time, the closest I come to improving the soil is to toss around any rotting logs, wood chips, stumps, broken branches (I make brush piles), rocks, leaves, or other natural materials that happen to come my way. My idea of mulch is to plant things so close together than no weed would dare to try to get in the way!

All of which is to say that I don't know much about the peat controversy because I don't have to: This is one of those environmental questions that, being largely into native plants, I get to skip on the test.

I'm grateful for gardeners who, like Jodi, take the time to do their homework and make environmentally responsible choices in their gardens. If you're looking for an easy way to be environmentally benign, however, think about gardening with native plants: You get to be virtuous, and it's a lot less work.

Coffee and the Garden

EARLIER TODAY a member of a gardening list I belong to asked whether coffee grounds are good for the garden and, if so, how to use them. I did a quick google on "+coffee +compost" and hit pay dirt (so to speak). It seems that Sunset magazine (a mag that's big on the West Coast) sent a batch of Starbuck's coffee grounds to a soil lab for testing. The results were so interesting that I thought they would be worth passing along here.

It turns out that coffee grounds are a great soil amendment, though they might tend to acidify your soil slightly. (They are about 6.2 on the pH scale.) They can be mixed directly with soil at a rate of about 1 part coffee grounds to 4 parts soil (to a maximum of 38% coffee grounds by volume), or they can be sprinkled on the surface of the soil where they will behave something like a mild, slow-release fertilizer.

Additional details:

1. The N/K/P balance of coffee grounds is 2.28%, .06%, .6%

2. Coffee grounds do not supply appreciable amounts of calcium, zinc, manganese, and iron

3. They do supply useful amounts of copper, magnesium, potassium, and phosphorus. The potassium and magnesium become available almost immediately.

4. Coffee grounds do not supply large amounts of nitrogen. However, as soil organisms break down the grounds they do release small amounts of nitrogen and other essential elements. In effect, this makes coffee grounds an excellent slow-release fertilizer. (And a lot cheaper than Osmocote!)

The full article is at http://www.sunset.com/sunset/garden/edible/article/0,20633,1208232,00.html.

By the way, don't forget to buy shade-grown coffee, which preserves habitat for birds and other animals. For details see http://nationalzoo.si.edu/ConservationAndScience/MigratoryBirds/Coffee/