Friday, October 30, 2009

Making a Water Budget

Okay, so you have decided to take a good, hard look at how much water you are using on your garden or landscaping and see if there is a better way to do it. The first step is to figure out how much you are getting and how much you are going to need. If it is starting to sound like basic budgeting, you are right. It is time to make a water budget. My city, Prescott, Arizona, USA, has a really good worked example for the locals here (link downloads a .pdf file). The basics are actually very simple.

First, you need to separate your planted areas by water requirements. Are they xeriscape, garden, turf, or native landscape plants? Garden and lawn take the most water and are generally considered oasis areas. Non-native landscape plants and fruit trees typically take less water than an oasis area, but more than native vegetation. Native plants and xeriscape plants usually need additional water only in a drought. Then you need to figure how much water you are going to need for each area. Prescott's numbers are probably pretty good as a starting point. Prescott is above 5,000 feet in elevation in Arizona, so it doesn't get excessively hot here (typically 5 or so days a year over 100 degrees F), but it is very dry, typically in the 10-30% humidity range. We do also get normal winters, being in USDA Zone 7. So you may have to adjust water requirements just a little to fit your area: up for hotter, down for cooler, down for more humid. It may take some trial and error. For Prescott, oasis areas require 8" of water a month during the growing season and 1" per month during the dormant season. Trees require 45 gallons a month during the growing season and 4.5 gallons a month during the dormant season.

Secondly, you will want to look up your rainfall data. I get mine from the Weather Channel page, which has monthly averages. Given the nature of climates, much more accurate data than that isn't actually going to be more accurate.

Lastly, you just calculate how many inches of rain you are going to need for your landscape in a given month and subtract from that how many inches you are likely to get. The difference between the two is the amount you have to add to your garden or landscaping to keep it alive and allow it to thrive. That water can come from your tap, gray water, or from captured rainwater.

There really isn't much to say about tap water. You turn on the faucet and it comes out. It is super easy and reasonably cheap, but not necessarily the best solution. If you are in an area that is short on water, and most are these days, it drains the local supply and increases shortages. Also, while water doesn't cost too much, neither do vegetables. How much water does it take in your garden before you are paying more for the water to grow your veggies than it would have cost to get them at the store?

Gray water involves double using SOME of the water from your house. I will cover that in detail in a future post.

Capturing rainwater is another good way to get water and there are two basic ways to do it. The first is to shape your land so that it collects water and the second is to collect rainwater off of the roof of your house. I'll also cover those in upcoming posts.

Finally, remember that just because you get more water than you need in a given month, it doesn't mean that it will arrive when you need it. Tap water is a really great backup system.

Wednesday, October 28, 2009


The first freeze has hit with a vengence here in my area and it is finally time to harvest some of the fall veggies. There are certain vegetables, like kale (especially red russian), collards and jerusalem artichokes that really shouldn't be harvested before the first freeze. Freezing temperatures actually sweeten the vegetables, making them much tastier after the frost than before.

But why is this? Well, it usually happens with veggies that are capable of keeping green leaves going well past the first several light frosts. In the case of jerusalem artichokes, they are adapted to northern climates and keep their tubers above the frost depth, which can be several feet in parts of their habitat. In both cases, the plants need a natural antifreeze in their flesh that keeps the ice crystals from forming as long as possible.

Now, the antifreeze in your car is seriously dangerous stuff. It is loaded with different kinds of sugars that keep the water from freezing, but it also has pump lubricants that help all the machinery running. The sugars make it taste yummy to animals and children while the lubricants kill them.

Plants basically use the same system to keep themselves from freezing, without the toxic side effects. By upping the concentration of sugar in their flesh, they keep the damaging ice crystals at bay. In the process, they make themselves sweeter and thus tastier.

Friday, October 16, 2009

Raised Bed Garden or Sunken Bed Garden

When starting a garden, the goal is to maximize your advantages while minimizing your disadvantages. A raised bed garden is a good way to do this. By building a raised bed, you give your garden great drainage. You don't have to worry about poor native soil, either. You need to fill up the raised bed anyway, so you might as well fill it with the good stuff. A raised bed garden also helps bad backs by making it so that you don't have to bend over so far to get to your garden. In addition, there are other minor benefits, such as getting the garden up high enough that certain pests, like rabbits, can't get to it. If slugs are a problem in your area, a simple strip of copper ringing the raised bed will keep them out. Slugs and snails won't cross copper.

When I started my first garden at my first house here in Arizona, my goal was to create a raised bed. Materials were expensive and I didn't have a lot of money, so it was a long term goal. But after a few years, I discovered that a raised bed garden would not necessarily be a good thing here. In the arid southwest, good drainage is a bad thing. The more water you let drain away, the more you have to supply. All of our water here comes from the ground. The more you use, the more you pump out. The more you pump out, the less there is to go around. So conserving the water you have is a very good idea. In addition, we get close to enough rain to water everything. It just doesn't always come down when you need it. So the real way to make that work is to store as much water as you can when it does come and use it for the dry periods. A rain barrel makes for a good storage device, but it can become cost-prohibitive to buy enough to fully meet your needs. What you really need is a way to keep the water that hits your garden, a way to store the water in the ground.

A sunken bed garden does just that. It keeps the water from flowing away long enough that it can soak in. You then have the water stored in the soil itself, which will help the plants last longer between waterings, which means less water used overall. If your terrain allows, you can even shape the earth so that your sunken bed catches runoff from elsewhere. I will cover methods for doing that in a future post.

Another advantage for sunken bed gardening here lies in the soil itself. There isn't as much sand in Arizona as you might think. In fact, there is a lot of clay, and lots of that is expansive. Expansive clay works much like water-grabber crystals. When they are exposed to water, the microscopic particles expand and hold on to the water. In its natural state, this is a bad thing, and not just for your building foundations. During a rain event, the clay particles on the surface swell and seal off the pores in the soil. This means that the water can't really penetrate deep into the soil and just runs off, wasted. A sunken bed will help the water sit long enough for it to soak in. It still may just sink in a few inches, just enough to saturate the surface and cause troubles for the plants that don't like wet feet. To really take advantage of the water-holding properties of the soil, you need to amend the soil. When you first create the garden dig down a foot or more and amend with organic material, preferably composted wood chips. The wood will have some lasting power in the soil. Ideally you'll have as much as 50% of the volume of the soil as organic material. This will open up the pores of the clay and let the water soak in deep. The clay particles will still swell and hold the water, but now more of them can do the work, delivering it slower and holding it over a greater area. Also, if you treat the soil with a mycorrhizal fungus, the fungus will travel through the organic material, better surviving than in a soil that is poor in organic material. It will then send its filaments throughout the soil and grab the moisture that the plants can't reach and deliver it to the plants.

So, how do you design one of these? I'll cover that in a future post as well, so stay tuned. For now I'll just say that factors like local rainfall, soil and what you are planting all come into play. I will also say that this sort of design is ideally suited for landscaping and will give you a lower-maintenance landscape. It is a little trickier for vegetable gardening.

Wednesday, October 14, 2009


Mulch is amazing stuff, and probably my biggest area for improvement in the garden would be to be more judicious about using it. Mulch has so many uses in the garden and landscape. It cools the soil. It holds moisture long enough for more of it to penetrate than bare soil. It allows moisture to penetrate deeper into the soil and keeps it from evaporating as fast. It smothers weeds thus reducing weed problems in your landscape. Most importantly, it feeds the soil by providing a slow, constant source of organic matter to feed the micro- and macro-organisms in the soil.

It is worth noting that I am almost exclusively talking about organic mulches. There are also inorganic mulches, such as plastic liner, gravel, decomposed granite, river rock, and landscape fabric. Plastic barriers do a great job of keeping out weeds and keeping in warmth, but they smother the soil, preventing oxygen and moisture from reaching the soil. If you remember that soil is a living organism, you might see how smothering the soil is a bad thing. I also don't particularly like rock mulches since leaves and weeds have to be removed regularly or they look bad. It is a lot more work maintaining rock mulches in an attractive fashion than it is to maintain organic mulches. I will say, though, that mulches made of large rocks can create a useful micro-climate where needed. The rocks absorb heat to help heat-loving plants in cool climates and can act as a thermal mass, protecting tender plants from some of the harshness of cold nights.

As far as organic mulches go, there are a number of different kinds, each with their own benefits and disadvantages:

Yes, compost can be considered a mulch. It shades the soil and helps water penetrate. In addition, it provides a phenomenal benefit of nutrients and beneficial bacteria and fungus to the soil. As for disadvantages, it may not prevent weeds as well as other materials and it doesn't give that neat, clean, landscaped look that other mulches provide. It just looks like black dirt. Also, if you are making your own, it is really difficult to produce enough to provide enough that it actually counts as mulch.

This one is really nice for the veggie garden. You usually want to apply it a little thicker than other mulches to get the same weed protection. It does break down rapidly, though, and it makes a great soil amendment.

Wood Chips
This is one of the easier mulches to come by. Wood chips make your landscaping look nice and neat. They also take a long time to break down, giving them lasting power in your landscape. Conventional wisdom is that woodchips also bind nitrogen in the soil, holding on to it until they are broken down. This can be a good thing and a bad thing. On the bad side, they can rob your plants of nitrogen and stunt their growth. On the good side, they do the same thing to weeds.

Fallen Leaves
When the leaves fall off your trees in the autumn, they usually get thrown in the compost bin (or, heaven forbid, go out with the trash). But they can also be used as a mulch. One of the big advantages is that if you have enough moisture, the two dimensional nature of the leaves comes into play and they stick together to make a dense mat. It can be so dense that if left on a lawn, just a few inches can kill your lawn. The grass can't penetrate it, and neither will weed seedlings. It is also great food for the fungus and worms in your soil.

Cocoa Bean Hulls
I am still looking for this mythical mulch. A neighbor had some a few years ago and it made her whole garden smell like brownies. It also looked pretty nice. The only problem is that some dogs find it irresistible. The chemicals in chocolate, including the hulls, can kill a dog. So use this one with care.

Grass Clippings
Fresh grass clippings are very high in nitrogen and moisture. If you put a big pile of them on your landscaping, they will get smelly. However, if you spread them out to dry or just put a thin layer on your landscaping or garden, they will dry out pretty quickly and add a little nitrogen to your soil.

Wood Pellet Fuel
Wood pellets are made specifically for pellet stoves. They are sawdust that is dried and compressed to make pellets. The nice thing about them is that when you add water, they swell to several times their original size. Plus, a 40 pound bag sells for about $4.50 in my area. The resulting mulch is a bit finer than I usually like, but it really is pretty nice. I will offer a caution, though. I haven't found much information about what is in them, so I always look for one that says "100% Organic" or "100% Wood" or something of the sort on it. I don't think they put additives in it to help it burn, but it'd be good to know for sure. Also, it is generally only available in winter.

Cardboard and Newspaper
Cardboard and newspaper work in much the same way as landscape fabric or plastic sheeting with the added benefits that they are cheap or free and will biodegrade over time. Few organic mulches are better for weed control than a nice layer of cardboard or newspaper. In my experience, these usually work best with wood chips or some other material on top. You need something to hold them down or the wind will pick them up and put them somewhere else.

Sunday, October 11, 2009

In-Situ Composting

I am nearing the end of my first season of gardening in my biologically active container garden and that means it is time to assess successes and failures. Successes are pretty simple. The swiss chard and turnip pot was wildly successful and still is. The varmint protection systems had to be upgraded a few times, but ultimately held against some pretty determined varmints. Finally, my multi-layered pot, with beets in front, dill and cilantro in the middle and okra in the back, fared very well and provided a solid wall of green all summer long.

Failures were pretty easy to assess as well. I tried to grow marigolds and nasturtium as companion plants and both grew quicker than the plants they were supposed to help and took over. So next year the flowers go in the ground, not the pots. Eggplants, beets, tomatoes, beans, chervil, onions and gourds all failed to reach their potential, though of those the beets fared the best.

The biggest issue, though, was the soil. My starter soil was the leftovers from a myco-vermicomposting experiment I had done several years before. The soil was black, fine and a little sticky. My plants absolutely loved it. The problem was, there wasn't enough to go around. So I spread it out and thinned it out with composted and partially composted remnants I had around. Then I bought some composted wood chips from the local nursery. A few pots had several inches of this stuff on top. To all of this I added blood meal, bone meal, and an organic mixed fertilizer containing rock phosphate and greensand, among other things. A few plants seemed to lack nitrogen, but otherwise nutrients seemed to be fine. The plants in the pots that were primarily my homemade soil did just fine. The store-bought compost, however, was problematic. It was too chunky and made for excellent drainage. So excellent, in fact, that the plants couldn't manage to collect the water before it drained away. Seedlings would sprout and then dry out, despite being watered twice a day. The plants that made it floundered and failed to grow much.

In an attempt to get some well-needed soil amendment, I am going to be trying something a little new. I have previously tried composting at my house, but without some draconian measures, it has proven difficult to keep the javelinas out of my compost. They break into my container, break the container, and either eat or make a mess of the contents. For the last several months I have been giving my compost to the neighborhood bins. However, this weekend I was able to fully put one of the pots to bed for the winter, harvesting what remained of the beets and pulling up everything else. Since this bin has already proven itself javelina-proof, I pulled the soil out from the middle and pushed it up the sides, giving me a good place to put all of my scraps and trimmings. I also encountered a number of worms while digging, which means that they are there and ready to do my composting for me. With any luck, some or even most of it will be composted and ready to use by spring. Then I can use it to boost my soil for better nutrients, better biological activity, more worms, and better water-holding capability.