If you were lucky enough to start from scratch on a new site or even if you are digging in a few vines in your backyard, this page will help you figure out what you need to do.
Soil in the Puget Sound AVA
In the Puget Sound region, there isn’t a lot of variation in soil types. That’s because most of the lowlands in the Puget Sound AVA were under a massive glacier 10,000 years ago. This glacier extended out of Canada and terminated in the Chehalis region. The ice sheet was almost a mile thick in many areas. The glacier scoured almost anything in it’s way and ground it up into sand and flattened any prominent surface features. When things warmed up the glacier retreated and upon melting it dropped massive amounts of sand and rocks in long hills of debris.
As anyone knows that has a garden here in the Puget Sound lowlands, we are constantly digging up potato sized rocks. They are everywhere and that is good for growing grapes. That helps keep the soil free draining and loose. The typical soil of the Puget Sound AVA, mainly on the hills, is called the Alderwood series. Alderwood soils are typified by good surface drainage and are made up of a rather course texture from gravelly to sandy loam, which grapes really like. The problem is that there is usually a hardpan layer below the topsoil and subsoil that was created when the glaciers sat on top of the ground, compacting the lower soils into a hard concrete like material. When it rains that water can pool on top of the hardpan creating areas underground that store water or create springs that seem to pop up in the middle of nowhere.
The other issue is that grapevine roots can have trouble penetrating the hardpan. The topsoil are usually 2-3 feet thick before you hit the hardpan. Generally, I have not experienced any problems with a hardpan in my vineyard, but if you dig some pilot holes around your location you can see how deep your topsoil is. On larger locations, you can hire a bulldozer with a ripping tool to rip up the hardpan allowing better drainage. On a hobby level, digging a deep hole into the hard pan with a post hole digger can help give room for the roots. Also, rootstocks generally have a shallow root structure than own rooted vinifera grapes and are perfectly happy to grow in shallow soils.
There are, of course, other soils from sandy to heavy clay but ideally you will want to avoid those for a vineyard. If you can’t escape them because it’s the only land you have available, there are ways to fix them that I will not cover here. Please reference a good gardening book that can tell you how to fix your soils, but on a large scale (acres of land) it may not be something you want to tackle.
There is one other issue that you might have to address in your vineyard here in the Puget Sound AVA in the Alderwood series and that is the lack of boron. The glaciers stripped out the boron and it is an essential mineral for pollination. It is simple to fix by applying Boron to the soil or to spray directly on your vines when they have leaves on them. If you test you soil and it’s boron deficient then this will be a must do or you will have weak fruit set.
Also, the soils in the Puget Sound tend to have a large amount of Nitrogen (N). The soils tend to be vigorous and grape vines grow profusely in these soils given enough light and water. There are ways to mitigate the growth of the vines, as we will discuss later.
The first thing you want to do is get your soils tested at a lab. It’s not that expensive and easy to do. Even though the soils are pretty similar all over our region, it’s still a good idea to get them tested. Most people I know have used one lab and it http://www.al-labs-west.com/ in California. They have instructions on exactly what to do and will even send you sample bags. Make sure you ask to have the results show you what amendments you will need for grapes. They will tell you exactly how much of what minerals you need to add per acre. After you have an established vineyard a petiole test is a better indicator. We will discuss that later.
Generally what you will find is that you need to add lime and lots of it. I think my soil test said 4 tons an acre since our acid levels are pretty high. I ordered 4 tons of dolomitic lime and laid it down with a drop spreader. About 100lbs per row. I also put about a 1/2 cup of Cal-Mag fertilizer around each vine. I spray boron on my vines each year so I didn’t put it in the soil.
Site Preparation
After you have your soil tested, it’s time to start getting things ready. I’ll cover grape selection after this, but ideally you will order your grapes in the Fall before you are ready to plant. About the same time you can start getting the ground and structures taken care of. It’s best to work the ground when it has been raining recently and the soil is moist but not soaking wet. Puget Sound soils can kick up a lot of dust and make it really hard to work when it is the middle of the summer. It’s best to try and work the soils after a couple of good rains. Before you plant your vines, you need to remove as much of the grass and weeds growing on your future vineyards as possible. Rototilling is the prefered method to do this. You might have to do it several times to remove all the old grass. If you had blackberries or trees, it might take a year or two to get rid of everything. You might have to use a bulldozer to do this. Keep that in mind when planning. If it’s just your backyard, just make sure the area around vines is going to be free of grass and weeds by at least a foot on all sides. Do not use plastic mulch or landscape fabric. Voles, mice and rats will use this as a way to get around and can cause all kinds of issues.
This is also a good time to rip the soil if you think you have a drainage issue. Renting a bulldozer with a subsoiler to rip into the hardpan might be a good idea. This helps break up the hardpan so the vines roots can access more water in the middle of a dry summer.
Basically, there are two ways to accomplish the task of removing ground cover and that is by using herbicides and/or a rototiller. If your vineyard is small enough, a shovel might work but when it gets to be more than a handful of vines, a good rototiller is much more efficient.
The reason you want bare soil is so the vines grow without competition from weeds and grass. They need abundant water and other resources to grow into large vines in a short time. You want at least a foot around each vine to be bare soil. You need to keep it this way for the first 2-3 years. Also, weeds and grass can grow pretty tall around the Puget Sound and can interfere in training the vines and grow up into the trellis, causing problems with the fruit and vines.
Trellis and Irrigation
It’s a good idea is to install your trellis posts and wires before you plant. Again, I am not going to go into a lot of detail here because that is covered in other books or online resources, but I wanted to discuss the unique features of trellis design in the Puget Sound AVA.
Because of the nature of the climate in the Puget Sound region and the grapes that we grow, we mainly use what is called a Vertical Shoot Positioning (VSP) system. This differs from Eastern Washington and California where it’s much hotter. Cooler climates seem to benefit more from a VSP system. Probably because it allows for a larger canopy of leaves and also allows for exposing the fruit to more sunshine, which is not a problem in the Yakima valley.
This picture shows basically how the vines are trained and what kind of wires you need. Generally, we plant vines 4’-6″ (depending on variety in the row. We want the rows to be 6’ or more apart. 6.5’ or 7’ are better when there is a full canopy growing and it makes it easier to drive a tractor down the rows. The first wire height is generally about 24″.
Designing the trellis system, we need to have end posts, middle posts, wire and tensioners. Depending on how long your rows are, will decide on how big your end posts are and if you need support for them so they don’t fall over when you have a full canopy on the vines. Generally, end posts that are around 4” thick are good unless you go with steel posts. Actually, there are 7 wires. A single wire at the bottom called the fruiting wire and then three sets of “catch” wires that are moveable. The reason they are moveable is so that you can pull them apart to train the new shoots to grow between them. The bottom wire is attached to the trellis with a wire tensioner to keep it tight. The bottom wire is usually made out of 12.5 gauge high tensile galvanized wire which is hard to work with and you will need a spinning jenny to install the wires. Modern trellis systems are mostly made out of steel posts now. They work much better on a large scale and are very good on the environment compared to pressure treated lumber.
After you have your trellis, you should put in an irrigation system, even if it’s temporary. Most people don’t realize that the first 2-3 years of the vines life, it’s going to need a lot of water. The Puget Sound region typically goes into drought every summer and if the young vines don’t get enough water they will die. The good news is that most of us have access to plentiful water all summer long.
Depending on how many vines you have will dictate how big of a watering system you’ll need. If you just have a handful of vines a soaker hose or hand water will be fine. For a full sized vineyard, putting in a temporary irrigation system is the most efficient way to water many vines at once. I’m not going to go over irrigation systems here, but I bought all my equipment at Home Depot for a nominal cost. The most expensive parts are the drip emitters. Most vines will need at least a gallon of water a week or more during the hottest parts of the summer. Once the vines are established, after a minimum of 2 years, you can pull up the drip lines and use again on a new vineyard. If you are in a really dry area, like the San Juan Islands, or on very sandy soil a permanent drip irrigation system might be a permanent fixture in your vineyard. In most locations around the Puget Sound, the irrigation system will not be needed after the 3rd year as the roots will be deep enough to tap into the ground water.
If you are a commercial grower, fine tuning irrigation might help you have a more quality crop. Like I said, there are whole books on irrigation. The book “Oregon Viticulture” is closer to our needs in Western Washington then some of the publications out of WSU (Washington State University).
After that, you are ready to plant the vineyard!