Sand box soil in need of improvement - Under layers of sand and weed barrier cloth. Compacted and receiving no organic matter (no leaf drop etc.)

So you can’t improve your soil by changing the texture (see last post), what can you do?

Well, first I need to clarify exactly what most people want from their soil – what exactly is the goal of “soil improvement”? Well, in most instances the ideal soil has the following properties:

1) Well draining – After a soil is saturated, a  certain amount of the water drains out  quickly so that there is both air and water in the soil pore spaces. Roots need both water AND air to function. Water-logged soils often lead to root rots and plant death.

2) Good water holding capacity – Ah, sounds a bit tricky to have soil that both drains well AND holds on to water well but that’s what we’re looking for.

3) Good infiltration rates – This is how quickly water enters the soil.  You don’t have to stand there with the hose turned to “slow dribble” to prevent water from running off or lose your soil to erosion as it is entrained by water during a storm.

4) Good nutrient holding abilities – Plants need nutrients, they are held in storage in the soil. You need adequate “storage” facilities.

5) Easily penetrable by roots – Okay, if you have good drainage chances are roots will also be able to move through the soil fairly easily.

If your soil is lacking one or more of these properties, you probably want to improve it. How?

Granular soil structure (good). (Picture from NASA soil science website.)

Well, I established in the last post that you can’t change a soil’s texture, but you can change a soil’s structure. Soil structure is the way in which the individual mineral grains and organic matter in the soil join together to form clumps or aggregates. You want your soil to form aggregates because you end up with a variety of pore sizes. Little pores are good at holding onto water and larger ones drain quickly providing air pockets for the roots.

Soil structure is easily destroyed and slowly built (excessive tilling, particularly when wet, and compaction are two ways to destroy soil structure). Clay soils tend to form aggregates because the clay pieces in it have a lot of – are you ready for it? – unsatisfied surface charges and they stick together like little magnets. Organic matter is also a fabulous glue. Fungal filaments, and various secretions and excretions by things living in the soil stick soil particles together.

Soil loosened with fork demonstrating massive structure (not good)

Sometimes in the top layer of soil, most of the soil aggregates are actually worm castings (worm poop). The soil passes through the worm’s gut (along with the organic material it means to eat) and everything gets altered and glued together. So keeping adequate organic matter in your soil (about 4-10%) hugely benefits soil structure and improves your soil.

Don’t just willy-nilly add piles of organics to your soil, however. (See Dr. Linda Chalker-Scott’s discussion of this.) Too much organic material can actually be bad for the soil. Get a soil test before you act. A variety of labs are available to do soil tests. I send mine to UMass Amherst because it’s cheap.

Soil had a surface layer of clay (pale) that is the remnant of former sod (mesh netting still in place). This layer will inhibit infiltration. I worked to incorporate it into the rest of the soil.

To summarize:

To improve your soil, disturb it as little as possible (minimize compaction and tilling), maintain adequate organic matter and preserve soil life – those earthworms and other soil organisms will do a lot of the work for improving your soil if you let them – so minimize herbicide/pesticide use.

Texture triangle

You often hear that adding organic matter to your soil will improve its texture. WRONG. You can’t, practically speaking, change a soil’s texture. Period. Don’t even try. You can’t do it by adding organic matter because what makes a soil’s texture is the percentage of sand, silt and clay sized particles that make up the MINERAL portion of the soil. Notice that organic matter is NOT one of the things that gives a soil its texture so adding it can’t affect the texture.

Gardeners care about soil texture because it plays a key role in various soil properties that affect how well plants grow  – water holding and draining abilities, nutrient holding capacity, how early in spring a soil can be worked, etc.

Now everyone wants to have a loam soil. A loam is a kind of  soil texture (see triangle); it has about equal amounts of sand and silt and between about 8 and 30% clay.

I’m not going to go into why soil texture affects soil properties but in general you can assume the following:

1) Sandy soils – can absorb a lot of water fairly quickly without it running off; dries out quickly so you need to water more often; water doesn’t spread out within the soil so you need to put soaker hoses or drip irrigation heads close together; it doesn’t hold onto nutrients well and is more likely to lead to pollution of ground water because water (and the dissolved nutrients in it) pass through it quickly

2) Silty soils – tend to erode readily; have fairly good water holding capacities and reasonable water draining capacities and nutrient holding abilities

3) Clay soils – are difficult to re-wet if they dry out and it must be done very slowly; once wet they stay wet for a long time; root rots due to water-logging are much more common than in other soils; nutrient holding capacity is high.

And the loam? The best of all worlds – good drainage AND good water holding capacity AND excellent nutrient holding ability.

How do you know if you have a loam? There are two methods you can use to find this out at home. Go to http://www.puyallup.wsu.edu/soilmgmt/Videos/Video_SoilTexture.htm for the “feel” method and to http://www.finegardening.com/how-to/articles/hows-your-soil-texture.aspx for the “jar” method.

Jar test @45% sand, 54% silt and 1% clay - a silty loam

So why can’t you just add what you need to your soil to turn it into a loam? Think about it. Let’s say you have a loamy sand at about 80% sand, 19% silt and 1% clay (not atypical where I live in the Puget Sound area of Washington). To get to a loam I would need to have about 50% sand, 40% silt and 10% clay.

Now what is coming is not exact, it’s just to give you an idea of how unreasonable it is to think you can change a soil’s texture.

Let’s start with a 1000 lbs of soil, that would be 800 lbs of sand, 190 lbs of silt and 10 lbs of clay. So you go find a source for pure silt (that’s convenient and reasonably priced, ha ha ha) and get about 500 lbs of it. Then you go find a source for clay (again, ha ha ha) and add about 140 lbs.

Now you’re at a total of about 1640 lbs of soil (in a space that formerly held 1000 lbs) that is approximately 49% sand, 42% silt and 9% clay. Okay, that works. Now mix it in so everything is evenly distributed throughout the soil.

Of course 1640 lbs of soil (assuming about 80 lbs/sq ft) only comes to about 3/4 of a yard. (A yard is a cube 3′H x 3′W x 3′L.) That would cover a bed that is only 4′ x 5′ to a depth of 1′. How big is your yard?

It’s just not practical, and may not even be possible, to change a soil’s texture. So how do you “improve” your soil?

Next post. It won’t be 8 months, I promise.

Low maintenance planting

IPM was developed for agriculture, where people’s livelihoods rest on the yields and appearance of what they produce.  Consequently, preventing and controlling pests, diseases and weeds that can impact the bottom line is essential.  To protect that bottom line in the least toxic, invasive and costly way possibly is how IPM decisions are made on farms.

The purpose of a home garden is different. Be it a place to play (lawn darts, soccer), relax, eat, grow food, welcome wildlife or merely to look good, our income is not dependent on what is happening in our yard. So the primary reason to control pests, diseases and weeds is aesthetics.  Clearly, if the ag people don’t need to totally obliterate whatever their problem is, neither do we.

So why all the pesticides and herbicides for sale everywhere?

I think there are two main reasons.

1. People are disenchanted with their gardens because they are too much work and don’t look all that good.  We hope that a bottle or bag will be a quick and magical cure-all when really the garden needs an overhaul and/or we need to learn a few low maintenance tips.
2. Bugs and lawn weeds have gotten a bad rap and we have succumbed to big businesses ads.

So the next time you think of reaching for a bottle of pest death, stop. Remember Canada, “pesticides should only be used when and where there is a need.” (See the 4/26/2010 post.) Then, make a list of everything that makes you unhappy in your yard and assess the causes.  Are the bugs etc. at the top of the list? Probably not.

One approach would be to ignore the bugs, etc. and deal with the higher priority issues and by the time you’re done, your pest/disease problem may be gone. If not, you will hopefully be so busy enjoying your new, improved, lower maintenance yard that you don’t care anymore.  If that doesn’t work for you, stay tuned.

I guess you could call this one IPM method #2 – re-thinking what is a problem.

They sure aren't letting this lawn go dormant!

The key to having a green lawn with less water is to pay attention and do a little digging.

• Make sure you’re giving your grass only the water it needs to stay green and healthy – no more. You’ll need to know your grass type and its typical water needs, and your soil type (sandy soils dry out more quickly than clay ones).
• Check the soil before you water – dig down through the root depth of the grass – have things dried out?
• Only water to a little bit below the root depth of the existing roots – again digging is the best way to find this out.
• Know how long it takes your sprinkler (irrigation system) to lay down 1″ of water.
• Realize that water loss (and therefore its replacement needs) varies throughout the season so you can’t just say, “I’ll add 1″ a week from June-September.” Sometimes that 1″ will be too much, others too little. A good tool to use to figure out how to adjust your watering is to look at the evapotranspiration rate in your area.

Evapotranspiration is the amount of water that evaporates from the soil and is transpired by plants – the water loss from the soil in other words. Of course these rates vary from place to place even within a small area. Is the soil mulched? What kinds of plants are growing and how densely? For example,” an acre of corn gives off about 3,000-4,000 gallons (11,400-15,100 liters) of water each day, and a large oak tree can transpire 40,000 gallons (151,000 liters) per year.”*

Nothing beats knowing your own yard but if you’re not willing to dig around in your lawn, using the evapotranspiration rate and the effective rainfall (if you can get that number, the table below has it as about 1/3 of total rainfall) will allow you to estimate pretty well how much you should water.

(Information in table from the Irrigation Water Management Project and the Saving Water Partnership. See http://www.iwms.org/seattle_area.asp)

Note the huge difference in actual rainfall (what ends up in the rain gauge) and the effective rainfall (what your plants can use) and compare that to the water loss (the ET rate). Cumulatively, from April to September, water loss in alost 20″ and what falls naturally and is available to plants is only 3″ and change. The rest you need to make up. Mulching will help retard evaporation in garden beds but you can’t really mulch the lawn so you need to replace that loss.

If your lawn is irrigated via an automatic timer, you need to change the settings over the course of the watering season or you will water too much (or not enough).

Angelica sylvestris (taiwanese) ‘Vicar’s Mead’ is one of those plants. With its mahogany foliage and airy flowerheads, it can get lost in a mixed border but put it up against a wall and its dusky, sculptural beauty becomes art.

This angelica is mostly a biennial [I had one come back for a 3rd year].  It self sows, heavily close to the plant for me, but it hasn’t wandered off into the yard and become a nuisance, at least not yet. It comes true from seed. Sun-shade, reasonably drought tolerant in shade here in the Pacific NW. Simply lovely.

Is this not the most pitiful August basil you've ever seen?

Okay, it’s a bad year for basil here in Seattle – We seem to be skipping summer altogether. An article in the paper said that we have had more low clouds this summer than any other on record (since 1951) – oh joy.

One well-grown basil plant that I had kept inside from mid-May to mid-July stopped growing (essentially) and ran to flower when placed outside. All the others either stopped growing or stopped growing and went to flower.  Sigh.

Running to flower is called bolting (running to flower, bolting, why does this action imply movement?) and some plants are more prone to it than others. Bolting is a plant’s attempt to make sure it sets seed before it dies. Lettuces bolt when things get too hot. Clearly that’s not the  problem with my basil.

Nope, my basil clearly thinks the cold of winter is on the way and it better stop all this frivolous leaf growth and put its energy into making the next generation. It is generally held that once a basil starts to flower, taste degenerates. That is certainly true for bolting lettuce. I haven’t noticed it with the basil, perhaps this is one instance in which having less-than-discerning taste buds is a plus.

I’ll post if the basils do anything unexpected in the next month (like grow) but I believe this marks the end of my experiment. Next year, I’ll make sure I keep one basil indoors and only let the rest out if we’re having a “good” summer – or I put in a cold frame. In the meantime, I’ll enjoy the leaves from my puny, bolting basils, until even my taste buds rebel.

Missoula, MT - brown hill, green trees - it's summer!

I went to graduate school in Montana. Before that, I’d never been west of Georgia where the grass grows green all summer. I still vividly remember how perplexed I was, upon arriving in Missoula in August,  to see that the grass on the hill behind the campus was brown.

“Aha,” I thought, “they recently had a fire, that must be it.”  Coming from the land of summertime rains, brown grass occurring naturally in the summertime was incomprehensible to me. But over the years, I’ve learned that brown grass is what you will have all over the west, even in the “rainy” Pacific NW, unless you irrigate.

Lawns are out of favor among many in the gardening world – too much maintenance, pesticides and water called for to keep them looking good but I think having a little bit of healthy, green lawn is nice. It sets off other plants. It’s pleasant to walk and play on and you don’t have to use pesticides and herbicides to keep it looking green and lush. You do, however, need to give almost all kinds of lawn grass supplemental summer water.

Given that the typical amount of water recommended for lawns is 1″/week (of course this varies with grass type, evapotranspiration rate that week, etc. but that’s another post) what’s a westerner to do? Be economical and environmentally friendly and let their lawns go dormant or water for that lovely lush green look?

I say water. Summer is when you are out using the yard, lying in the grass, playing ball, having picnics. No one wants to do that on scratchy brown sticks, but keep it as small as is feasible.

Why small? Check out the math below.

To water 1 acre of lawn with one inch of water:

1 acre = 43560 ft²

1 inch = 1/12 foot

43560 ft² x 1/12 ft = 3630 ft³

At 7.48 gallons/cubic foot (ft³) you need

27,152 gallons PER WEEK to cover one acre in 1 inch of water.

(I keep looking at that gargantuan number and trying to figure out how I did the math wrong – dont’ see it.)

Now 1 acre is a huge area but even for a 1/4 acre, a not unreasonable size for some suburban lawns, you’re looking at 6788 gallons/week. I don’t know what water costs where you are but there’s now way I’d be laying on that kind of money.  So what can you do to cut down on water costs if you have a lot of grass?

• Identify the part of the lawn you actually use (and perhaps see the most of) and water only that – let the rest go dormant.
• Decide if you really want to keep that much of the yard in lawn. If not, start thinking re-design. Plants aren’t you’re only option. Don’t forget about hardscaping (the ultimate in low maintenance, no water needs, an excellent place to have a meal or set up some chairs to soak up the sun – or rest in the shade).
• Do the above and consider some different kinds of lawn grass that require less water. Check out High Country Gardens and Nichols Garden Nursery for options.

More on plants and water in the next post.

The memory of those tomatoes lives with me, so every year I continue my haphazard quest for tasty tomatoes, with varied success, because growing tomatoes successfully in Seattle is not the slam-dunk it is in Atlanta.

Some summers are better than others but the problem is that in the hot (relatively speaking) summers one needs to water more often. I am at best a slapdash waterer – and that may be a primary cause behind my general lack of success with tomatoes even during the summers where the weather is favorable.

Think about a tomato plant, a good indeterminant plant might grow 8′ in a few months and produce pounds of fruit – a lot of resources go into making all that.

I just read that consistent watering is needed for tasty vegetable production in a new book I got – Incredible Vegetables from Self-Watering Containers.

Clearly most vegetables need plenty of water, but what exactly happens if they get a little too dry now and then, is it really so bad, does it actually affect the flavor? I’ll do some research and let you know.

Photo 1 - Basil from cloche - See it hiding down there?

Oh those poor little basils that I sent out into the cold last month, how they’ve suffered. Summer only started here in Seattle on 7/6 going from coat weather to 90° heat in the space of a day. I’m not kidding about the coat weather; the kids came home from watching fireworks on the 4th wearing heavy coats with the hoods on and that is what the poor tropical basils had been out in.

Photo 2 - Basil left out in the cold

I’ve been watching them over the last month not growing an inch, becoming steadily more holey and eventually being engulfed by plants that WERE growing. The basil in the milk carton cloche (photo 1) held up slightly better than the one just out in the cold (photo 2).  Aren’t they just pitiful?

The one I kept in the house grew modestly (about 2″ on what was about a 6″ plant) and appears to be in good health (photo 3). I planted it out 2 days ago after a couple of days of 90 degree heat and balmy nights (for Seattle that is in the 60s).

Photo 3 - Basil grown indoors

We’re having another run of chill so the night temps are going to be a bit concerning. Perhaps I’ll put one of my newly planted basils (there are 3 who weren’t part of the original experiment) in a cloche and see what happens with it.

The moral of the story is obvious – DO NOT plant your basils too early – wait, wait, wait.

This assertion is supported by the folks at Cornell University.  Each day a convergent lady beetle larvae may eat its weight in aphids while an adult can take out 50.  Since this is the kind of beetle typically sold for biological control,  it sounds like our aphid problem can be solved for an investment of  $13.95 (give or take) plus shipping. Right?

Wrong. Well probably not. Here’s why.

Many of the convergent lady beetles sold for bio control are collected in the Sierra Nevada Mountains of California where they overwinter. In nature, when spring arrives and the lady beetles awake from hibernation they fly off to look for food – which the collected ladybeetles do once they are released in your yard. It’s just what these ladybugs do when they come out of hibernation, even if food is available.

One website said some people’s solution to this problem was to glue shut the wings with a mixture of pop and water so the ladybugs can’t leave the garden. (Can you imagine trying to glue a few dozen ladybug wings down? – not to mention that it’s  just plain wrong.)

Gardens Alive believe they have a solution to immediate ladybug flight that doesn’t involve glue. They sell Sta-Home™ Lady Beetles which they say won’t fly away because – “Upon receiving lady beetles from the West Coast area, our insect rearing laboratory feeds the beetles a special conditioning diet for 2 weeks. The process of feeding and holding the lady beetles ensures that they are ready to attack your pests without the need for a “migratory flight”. They will remain in your garden as long as a food source is available.” I liked this quote because it gave me visions of rows of ladybugs lined up on lab tables doing calisthenics after  a well-balanced meal.

If Garden’s Alive ladybugs really do stay put and you do the math it seems like a total excess of ladybugs. There are about 900 ladybeetles per package, enough, apparently, to cover 1000 sq. ft. of garden. At 50 aphids/ladybug/day that’s 45,000 aphids/day. Even with a really high attrition rate, a lot of aphids will be required to keep those ladybugs fat, sassy and reproducing in your yard. Or so it would seem.

Ladybeetle larvae - always referred to as "alligator-like"

According to one research study 900 ladybugs may not be enough! Now there has been little research on just how many and how often you have to supply ladybugs to control aphids in home gardens. One study found that 1000 ladybugs were required PER SHRUB, released every one to two weeks to control aphids on roses. If so, and if using Garden’s Alive Sta-Home™  ladybugs that’s one package per rose plant every 1-2 weeks at $13.95/package – which is way more than I’m willing to pay to deal with the aphids on my roses. Maybe the people in the research study didn’t use Sta-Home™ lady beetles so you wouldn’t need so many? Who knows.

Regardless of whether 900 ladybugs is too many or too few, I’m going to take the easier route and spend my money on yet more plants which will be much more satisfying. Since I have a wide variety of plants and avoid pesticides my garden should be a haven for insects, birds, bats and other beasties that will control aphids without any input from me.

If I have some plants that are known aphid magnets (nasturtiums) where the aphids may get out of hand, I will attempt to watch them carefully and wash off the aphids before they undergo a population explosion. If I miss the early stages as I often do, I can keep washing, or remove the offending plant (my typical response). Maybe this year I’ll wait and see if the ladybugs follow the scent of honeydew (truly they do) to the aphid smorgasbord awaiting them.

Sources:

Garden’s Alive website (There are many sources for bought ladybugs. I just picked this one because it is a company I’m familiar with having received their catalogs for years.

Cornell University website

Grissell, Eric, Insects and Garden, 2001

Dreistadt, Steve etal., Pests of Landscape Trees and Shrubs, 2^nd edition, 2004