Sunday, February 28, 2010

Mediterranean climate

Believe it or not, the Seattle area is considered to have a “Mediter-ranean” climate.  Well, it depends on whom you ask. Factors such as amount of winter rainfall and specifics about latitude result in disagreements. According to the Koeppen climate classification, we fall within a cool, dry-summer subtropical zone (Csb), resulting in Mediterranean characteristics.  Some diplomatic experts call it “modified Mediterranean.” Whatever.  I decided to try to understand the classification and how it affects our gardening.

Over 50% of the regions that boast this climate are located around the Mediterranean Sea, hence the name. The defining characteristic is the wet winter/dry summer seasonal changes in precipitation. Mediterranean zones are situated in either hemisphere on the western side of continents, between latitudes of 30° and 60°.

During the summer, this climate is dominated by subtropical high pressure cells making rainfall unlikely. During winter, prevailing winds from the west blow from the sea bringing rain and stormy weather. In addition, most areas with this climate, such as Seattle, are backed by coastal mountains. The warm moist air from the ocean rises up the mountains, expanding and cooling. At the dew point, the moisture condenses and precipitates on the mountain's windward side. The climatic and geographic effects combine to result in high seasonal rainfall totals.

In fact, areas with this climate receive almost all of their rainfall  for the year during the winter season, and some may go 4 to 6 months in the summer without having any significant precipitation. Our summers are shorter because as you move north along the American west coast the winters become more intensely wet and the dry seasons shorter. Interesting!

All regions with this climate type abut large bodies of water, moderating the temperature. Comparatively, there is a small range of temperatures between the winter low and summer high. The mildness varies with altitude, elevation, and distance from the ocean.

Mediterranean climate regions support some of the highest diversity of species in the world.  While these regions cover only 2% of the planet, they contain 20% of the world’s plant species. It is a gardeners’ paradise! I’ve lived in Texas and New Mexico and I can tell you by comparison, we can grow A LOT of different kinds of plants here. Our diversity is quite remarkable. How does all of this affect the way we garden?

Smart gardening takes more into consideration than “what we CAN grow.” Our job becomes substantially easier and more practical if we select plants that thrive without coddling. Despite the prodigious number of days we receive rainfall, our summers are DRY. It makes sense to accommodate that reality. As you contemplate acquiring new plants, put some thought into how much watering they are going to require. If you can’t live without those water craving prima donnas, plant them all together not spread out through the garden.

Check out the drought tolerant (xeric) planting areas of local public gardens. For my area, that includes the Bellevue Botanical Garden and the Center for Urban Horticulture Mediterranean(CUH) in Seattle. The Miller Garden in Seattle has a lovely Mediterranean hillside  facing west. Peruse the planned borders featured at High Country Gardens and see how beautiful xeric can be!  The Elisabeth Miller Library has resources including a list of books. Educate yourself now and enjoy the results this summer!

Friday, February 26, 2010

About that compost...

So, um….yeah, you know the rash promise I made? That I was through talking about compost for now? Well, my intentions were honorable, but how can I ignore the plea of a reader? After reading my previous posts, the question remained, “Okay, compost is good, I get it. What the heck is it?”
Compost is a soil amendment or a medium for growi10-11-07_1705ng plants that is created by decomposition of organic debris.  Composting is a natural process; it starts when vegetation falls to the ground.  As it slowly decays it provides nutrients needed for microorganisms, plants, and animals.  If you have walked through the forest, you have seen compost on the ground-lovely humus that is dark brown or black and has a soil-like, earthy smell.

Compost that is purposefully created is ready sooner than at nature’s measured pace and usually produces temperatures high enough to destroy pathogens and weed seeds that natural decomposition does not destroy. Ready to use compost is available in bags at nurseries and home improvement stores or in bulk from compost producers where you can pick it up or have it delivered.
Compost makes terrific mulch, but not all mulch is compost!! Some mulches, such as bark or wood chips are organic materials, but they have not been composted. The larger the pieces, the longer it takes to decompose. During the years you are waiting, all the available nitrogen in the soil beneath these mulches is utilized by the microbes doing the work, leaving none available for your plants. It kind of defeats the purpose of mulch!  Other mulches, like gravel, are inorganic and will never biodegrade. These have their own specific uses, but it is not to make the soil more fertile.
Not all compost is created equal. Be sure your compost is 100% vegetative materials or, if you prefer, contains a small amount of horse, chicken or cow manure.  I was once talked into buying compost that contained “biosolids”-perfectly safe, completely sanitized, ecologically friendly, right? While spreading the mulch, I encountered band-aids and other debris that had me ready to put my house up for sale.
Don’t go there; I don’t care what they tell you.  In a Biosolids Fact Sheet presented by the EPA, I found that “Limitations of biosolids composting may include:
• Survival and presence of primary pathogens in the product.
• Dispersion of secondary pathogens such as Aspergillus fumigatus, particulate matter, other airborne allergens.
• Lack of consistency in product quality with reference to metals, stability, and maturity.”
I don’t know what the heck Aspergillus fumigatus is, but I know for certain I don’t want it.
If you are shopping for compost, you will also run into soil and blends. One thing at which compost does not excel is filling raised beds-for this you need topsoil. There are many compositions which are sold as “topsoil”; a common “3 way mix” contains soil, sand and compost. Sometimes sawdust is included, sometimes manure. In my opinion, these do not serve well as mulch.  However, if you try to use straight compost to fill your beds, you will battle the forces of decomposition for a long, long time. The compost will continue to decompose and compact over time, your bed will sink and you will end up having to dig up all your plants and redo it. If this sounds like the voice of experience, that is because it is.
You can also make your own compost. All composting requires three basic ingredients:
1.       Carbon (Brown): dead leaves, dry grass, straw
2.       Nitrogen (Green): grass clippings and other vegetative waste
3.       Water
The water is necessary to help breakdown the organic matter. Having the right amount of greens, browns, and water is important for compost development.  The preferred ratio of brown to green materials should be about 3 to 1.  If you have too much brown, you’ll still get compost, it’ll just take a little longer. If you have too much green, you’ll likely have a smelly pile of rotting vegetation. The smaller the pieces are, the faster it will break down, so chip or shred what you can. At its most basic: make a pile with the shredded greens and browns; moisten with water. It should be the dampness of a squeezed sponge. Add a little soil or finished compost to provide some microbes. Turn with a pitchfork every week or two and in one to four months you’ll have your own compost.
The EPA has a terrific website about composting with all kinds of information, including composting facilities by state and helpful publications.  If you are interested in this topic, there is more info on the web than you could possibly assimilate. From expensive tumbling manufactured composters to composting fall leaves in plastic bags; from what NOT to compost to the chemical analysis of carbon to nitrogen ratio of various materials. Whatever you want to know, it’s out there. So, Google it!

Thursday, February 25, 2010

What's blooming now?

So far I've been pretty pleased with the show. Beginning in January I had Galanthus, which may be my favorite early bloom. Their delicate white and green blooms would be lost in the biomass of any other season. But in winter they bravely push their heads up, sometimes through the snow, while there are no other flowers to be seen. They are extremely hardy and will slowly colonize if happy. They are a little finicky in that they like to be planted “in the green.” So, don’t waste your money on bulbs, but find a nursery or a gracious friend with snowdrops to spare and plant them while they are up and growing. Galanthophiles are not uncommon-check out this article from a British newspaper. You may have one right next door!

A new favorite January-February bloomer is Hacquetia epipactis; this dainty plant sports what appear to be five petalled flowers with yellow stamens. In fact, the five green “petals” are bracts and the “stamens” are the actual acid yellow flowers, extremely tiny and profuse. This plant may be classified as a ground cover, but in my garden it spreads very s l o w l y. It does seed itself, but only in the gravel of the path, not in the rich and loamy soil of the bed. I had three seedlings last year.

Eranthis, Iris reticulata, the spare but fragrant Viburnum bodnantense, and faithful  Hellebores all bloom in January and into February. Then the early bulbs spring up, crocus along with miniature narcissus and deep blue Scilla. Pink Chionodoxa burst open, looking like pale pink shooting stars against the dark mulch; the more common blue Chionodoxa is still hiding.  Corylopsis pauciflora is blooming, the pale yellow blossoms lovely against the evergreen background. Ipheion, pulmonaria and primroses are starting to flower. But as March rolls around, most of the earliest to bloom are done and the big spring show hasn't started. I'm on the hunt for more plants that bloom in March and April.

I do have two interesting rhododendrons that have early blossoms.  Rhododendron mucronulatum, or Korean rhododendron,  usually blooms in early March on bare wood. This year it bloomed in February, for about 3 weeks.  Once it matures, it will make a statement at this season, but right now it is quite small.

The other interesting rhodie is the evergreen Rhododendron racemosum 'Rock Rose.' This one is an early, fragrant bloomer whose red stems add winter interest and is happy in full sun here in the Pacific Northwest. The species is quite variable in size; the smaller forms may top out at 1 foot and the largest may be a rangy 12 feet. There is a medium sized specimen in one of the display gardens at Emery’s Garden nursery in Lynnwood, WA. I find that the new stems have the brightest color, so I keep mine dense and colorful with selective pruning every year right after it finishes blooming.

Don’t settle for a flowerless winter while you are waiting for spring to arrive! Check out the naturalizing bulbs and early blooming woodies that can brighten your garden. They provide a lot of pleasure in small packages.

Tuesday, February 23, 2010

Don’t tread on me

Whenever soil structure is discussed, compaction is addressed. You might wonder, “What is soil compaction and why does it matter?” Soil compaction is something you want to minimize to keep your soil structure and ecosystem in top condition.

At its most basic, soil compaction is structural alteration of the soil as a result of outside pressure.  If you have ever attempted breaking through hardpan while digging in the garden, you are well acquainted with severely compacted soil. Just so, it is also difficult for soil dwelling organisms, such as worms and even microbes, to tunnel and forage through compacted soil. They cannot get the air, space and nutrients that they need to survive. Talk about your huddled masses yearning to breathe free-give them some space!

Soil structure determines the ability of soil to hold and conduct the water, nutrients, and air necessary for plant root activity. A typical cultivated loam soil is approximately 50% solid material, 30% water and 20% air. Water and air move through pores in the soil between the solid particles. Soil compaction reduces total pore space, interfering with drainage. Resulting low soil oxygen levels are the primary factor limiting plant growth in landscape soils.

So, we see that soil compaction is detrimental because increased soil density limits root growth, drainage and a healthy soil ecosystem. Compaction in home gardens typically occurs during construction and later as a result of foot traffic, especially when the soil is wet. I garden in the Pacific NW, for goodness sake. The soil is always wet. Except when it is really dry. What can be done to alleviate this situation?

If you are planning a garden, you can cultivate compost into the top 8-10” of soil. Depending on the type of soil the compost should make up 25-50% of the top 8-10” when you are done. Clay soil will require the heavier application of compost. If your garden is already planted, consider a 3-4” layer of compost mulch every year to gradually create the ideal home for earthworms and beneficial micro-organisms as you improve the structure and drainage.

Restrict traffic through the planted area. I was taught that moist soil can reach 75% maximum compaction the first timeBeckypictures2 011 it is stepped on, and 90% by the fourth time it is stepped on. Mom was right; you shouldn’t play in the mud-or plant in it, either. Raised beds are one solution. Paths may be needed to divide the bed  into manageable sections to eliminate compaction in the growing area. Ideally, you should be able to reach all parts of the bed from either outside of it or from a pathway through it.  Good luck with that. I’m just sayin’.

Once you have begun to create good soil structure, avoid excessive cultivation. Soil cultivation is any activity that redistributes the soil. Farmers cultivate using a plow or disc to break up the soil's surface. In the landscape, this is usually done by hand with a shovel or fork. Even so, use moderation. There is some punditry that cultivation disrupts the soil’s natural structure. Some experts eschew mechanical cultivation, stating that it can pulverize the soil's structure and destroy earthworm populations, ultimately creating more compaction rather than less. For your entertainment, here is a forum where the subject is debated-sometimes heatedly! Apparently, there is no agreement between actual gardeners on cultivation, or any other topic, generally!

Actually, all gardeners can agree on certain basics. Good soil is crucial to healthy plants. Good soil is determined by its structure and by the health of its ecosystem. Organic amendments, such as compost, contribute to both. And that's all I have to say about that-for now, anyway!

Monday, February 22, 2010

It’s a jungle out there

My previous post initiated some pondering on the amazing properties of dirt. The preferred term used by horticulturalists and biologists is "soil." The complexity of this material is astounding. To help explain why it matters whether you mulch with compost, you have to look at the microscopic level. Healthy soil supports a vast number of organisms that enhance the soil structure, recycle nutrients, and even help to control disease by processing food through their systems. These include macro-organisms such as beetles and worms, but the majority of the work is done by the tiny guys.
The ecosystem in your soil is made up of an astonishing diversity of microbes that play an important role in forming the crumbly, aerated soil structure that plants need to thrive. Fungi and bacteria produce substances that bind soil particles together. Beetles and earthworms consume soil and excrete castings that increase soil's arability. These macro-organisms also create nutrient-lined tunnels for roots, water and oxygen.
Most soil organisms get their energy from breaking down organic compounds, but there are some that get their energy from light, some from inorganic sources such as carbon dioxide, and a small but valuable group that gets energy from oxidizing inorganic compounds.
Plants need simple inorganic (non-carbon) forms of nutrients. Soil microbes create the nutrients plants need out of the raw materials available: organic and inorganic. They do this in several ways. Microbes speed up the decomposition process, during which acids are produced that chemically combine to form stabilized organic matter. Other microbes convert organic matter into plant friendly, inorganic nutrients. This is called mineralizing and nematodes, for example, can produce hundreds of pounds of ammonium per acre per day. Wow!
Bacteria also transform inorganic material into different inorganic compounds. Probably the most familiar example is nitrogen fixing bacteria that convert a type of nitrogen from the atmosphere into forms that plants can use. The roots of legumes host these beneficial bacteria as do the alder trees of the PNW. Alder trees were early colonizers after the Mt. St. Helen's eruption and the reforestation of that area has taken place faster than anyone could have predicted. A similar beneficial microbe is mycorrhizal fungi which invade a plant's roots or feed on carbon compounds exuded by roots, but repay the favor by fixing atmospheric nitrogen into a plant friendly nutrient.
Soil organisms control disease by generating substances toxic to the disease causing organism. Some beneficial predators, such as nematodes and protozoa control population levels of the harmful organisms. Some microbes simply compete with them for location or food source and win. Hurray for our side!
So, how do you encourage a jungle of diverse soil volunteers to make your garden thrive? Most soil organisms rely on organic matter for food. Compost is a readily available, ecologically friendly way to inoculate the soil with a wide diversity of organisms and provide them with a high quality food source. In addition, you can protect your volunteers by minimizing compaction, restricting pesticides and improving water drainage. So, go get your compost and start spreading!

Sunday, February 21, 2010

Spring-Are we there yet?

So, it is mid February in the Pacific NW. Today it was breathtakingly sunny, almost 60 degrees, no wind. It feels like May. Some of you unfamiliar with our beautiful home may be watching the Olympics in Vancouver BC and thinking, "we gotta move there." I have bad news. This is highly unusual. Our winters are normally very wet; in 2006, for example, we almost broke our own record with 27 straight days of rain. Yes, I mean every day. My relatives who live in Texas think it is hilarious when our weatherman announces on the TV that he predicts we will have sun-breaks. I think when they say the chance of rain is 20%, they mean chances are, it is going to be raining for 20% of the day. Check out our local station's website; an article posted during that rainy streak makes the breathless pronouncement: "Sun makes brief appearance." I am amused, the photo with that caption shows no sun.
Surprisingly, we have what is considered a Mediterranean climate which, at its most basic, means mild and very wet in the winter and sunny and dry in the summer. This type of climate is extremely rare-to see how rare, check out the map on Wikipedia. Our sunny, dry summer is usually July-August. We used to joke that if summer came on a weekend, we were going to have a picnic. So, what do we do with a misplaced summer week in the middle of February? We shovel poo! Call Mike Rowe! 
Not really, it is actually some very nice compost we ordered from Bailey's Compost in Snohomish. It is about 10% well aged cow manure and the rest is shredded yard waste. There is no odor at all-which is probably because it has been "aging" all winter-and it makes a beautiful mulch. However, we got 10 yards and I've been moving it since Tuesday, so it is starting to lose its appeal. There is no question, though: compost is absolutely the best mulch you can use. An old adage says if you have $10 to spend on your garden, spend $1 on plants and $9 on dirt. That seems crazy, but soil is the key to beautiful plants. Good soil makes healthy plants; the best plants money can buy will still decline in poor soil.
Soil holds water, nutrients and organic matter that are required by plants. Soil is made up of particles; “loam” is a mixture of the two most common particles. Sand has the largest particles, so it drains the fastest and has limited ability to retain moisture and nutrients. Clay has the smallest particles, so it drains very slowly-if at all! Compost improves every kind of soil. Compost helps sandy soil to hold moisture and it breaks up clay, allowing moisture to drain. In all kinds of soil it provides air pockets and micro-organisms which are vital to the health and arability of your soil.
So, if you are starting a garden, be sure to work in plenty of compost before you plant. If you already have a garden, try spreading a 3-4" layer of compost mulch. It will keep down weeds, hold in moisture in the summer, prevent frost heave in the winter, look great and improve your soil. And you won't need to go to the gym for the week you are shoveling.