News from the Edible Demo Garden

Blueberries are the focus of the newest demo garden project. Blueberries grow on long-lived and attractive shrubs and are both delicious and nutritious. They can be an ideal addition to an edible garden or to a home landscape if their growing conditions are met. Whether these conditions could be met in the edible demo garden is the question driving the project. While strawberries and raspberries have grown successfully in the demo garden, blueberries can struggle in hot dry summers.

 

Growing Conditions for Blueberries

Blueberries are in the Ericaceae family and are related to rhododendrons and azaleas and thrive under similar conditions. They need:

• Full sun with some shade protection in hot weather
• Acid soil (pH 4.5 to 5.5)
• Ample water
• Good drainage

Much of our Marin garden soil is not sufficiently acidic for blueberries so it’s necessary to create it using pH lowering organic amendments such as peat moss or elemental sulfur. A layer of organic mulch will help keep the soil cool and moist and will protect the shallow roots. Regular feeding with acid-forming complete fertilizers will provide nutrients and help maintain the low pH.

 

Selecting the Best Varieties

Blueberries native to the northeastern US require too many annual chill hours (hours with temperatures between 32 to 45 degrees), to grow well in Marin. Fortunately, there are many cultivars with low chilling requirements available. Ripening time is another consideration. There are early season, midseason, and late season varieties. Planting at least two different varieties improves pollination and increases production, so choosing kinds that ripen at different times increases harvest length. Two hybrid “varieties were chosen for the edible demo garden:

• ‘Misty’. Classified as southern highbush variety, it produces very early, large, good-flavored fruit. It has a 150 to 300 chill hour requirement and tolerates a higher than usual soil pH.
• ‘Blueray’. It is a southern highbush midseason variety with a chill requirement around 500 hours. It produces large, flavorful berries and is more tolerant of summer heat than some other varieties.

 

Promoting Production

The best fruit production requires patience and careful pruning. Removing blossoms the first year or two allows the plant to focus its energy on vigorous growth. Initially pruning all branches back to about 30% also promotes new growth. In following years, older branches or weak shoots can be removed, but fruit is produced on 1-year old wood so excessive pruning will reduce yield.

For more information, see our grow sheets on blueberries! 

If the edible demo garden blueberry project is a success, the next problem will be keeping the birds from devouring the crop.

November and December are clean up times in the garden, as well as assessing the state of our garden after growing all of those heavy feeder summer vegetables.  We have recently removed our straw bales and like last year, we wanted to use the composted straw as a fertilizer.  Last year, a simple home test told us that our composted straw was very high in nitrogen.  In our horseradish bed, we set up a side-by-side comparison of the use of this decomposed straw as fertilizer versus the regular compost that the farm purchases.  On the composted straw side, the horseradish leaves sprouted way before the ones on the farm’s  compost side did.  The leaves were fully-grown when the other side was half as high.  By the summer though, the farm’s compost side had caught up and there was no difference between them.  We wanted to use this super fertilizer again but first we had to test the nitrogen level. 

 

Soil Testing for the Home Gardener

Every Master Gardener in our training class learns how to use a do-it-yourself soil testing kit that will give you a pH reading and the level of Nitrogen (N), Phosphorous (P), and Potassium (K) in your soil.  The kits we use are inexpensive (under $20).  The process involves dissolving pills in distilled water with a soil sample and after the soil settles, comparing the color of the water against a key that tells you the level of a particular nutrient.  Are these tests totally accurate?  Probably not, but they can give you a rough estimate of your soil fertility for the primary nutrients that are required in larger amounts than other soil nutrients. One piece of advice, do this with a buddy because the directions are complicated and it helps to have one person read them while the other one actually does the testing.  It is more fun that way too.

If you don’t feel like being a chemist, there are also nutrient testing kits you can purchase that just require you to send a soil sample to a lab for testing.  You get a list of the results and also some recommendations for amending any deficiencies.   These test kits are also under $20 but you have to pay the postage for shipping to the lab. 

Choose which method suits you best.  For Master Gardeners, getting your hands dirty and experiencing science up close and personal can feel quite rewarding. 

 

Soil Testing Results

We tested the pH and the nitrogen level in our straw compost and found out that the pH was perfect for growing vegetables. The Nitrogen level, however, was between low and very low.  So what was the difference between last year and this year?  In October, we had substantial rain:  17 inches for the reservoirs in Southern Marin and 7.6 inches for Stafford Lake in North Marin.  We left our bales in place during October because we were still harvesting winter squash and the rains came down hard on them. 

 

At the end of the growing season, the leftover nitrogen is mostly dissolved in water held in the pore space between the soil particles.  It is very mobile and probably was depleted by the onslaught of heavy rains as it was washed into the soil below.  So what we hoped would fertilize our soil will now be used as mulch which will improve the soil structure but not fertilize our plants. 

 

Compost to Increase Fertility for your Spring Garden

As a result of our testing, we will now go back to the tried and true use of compost to solve our garden fertility problems.  Even though our straw compost was a faster way to start our horseradish growing again, by the spring, the farm’s compost had proven to be just as effective even with the slower start. 

The nitrogen in compost is in a form that is not available to plant roots.  But it is slowly converted over time to a form that can be used by the plant.  Now is the time to apply compost to your winter garden plants and the also the parts of the garden that will be left fallow.  Also, adding a mulch like straw, for example, on top of the compost will help to conserve soil moisture just like it does in the summer. 

Let’s hope that we get more storms this winter but with the compost’s slow process of converting organic nitrogen to a usable nutrient, your garden will be all ready to go come spring.  As we Master Gardeners love to say, "compost, compost, compost"!

At the Edible Demonstration Garden this month, we have been following best practices for seeding our winter garden plants in the greenhouse. These practices were outlined in last month’s article.  This month, we will begin moving some of these seedlings into the garden.  Right now they are in the greenhouse with temperature controls and fans that keep the air moving.  Home gardeners do not usually have the benefit of a greenhouse. Even so, if seedlings are started in your home, it is still a much kinder environment than exists outside.   So what is the best procedure for moving delicate seedlings into your garden?

When is a seedling ready to move?

The most common problem with transplanting is timing.  Many gardeners, including our team, make the mistake of waiting too long. A good rule of thumb is that the seedling should have at least three to four true leaves in addition to the seed leaves that appear first. The height of the seedling is not as important as the number of leaves it has.  An ideal seedling would be as wide as it is tall.  So how do we toughen up that soft, succulent type of growth into a firmer, harder type?  This process is called ‘hardening off’.

Take the Time for Hardening Off

Your seedlings need a transition time to the harsher outside conditions.  If you do not provide this, a severe, long-term check in growth can occur.  The hardening process will take at the very least seven days or up to two weeks, so this requires patience.  Remember that you’re looking for the plant to lose those soft stems and harden up.  So observe your plants closely. 

Hardening Off Process

As you transition your seedlings to the outside, keep in mind the two elements that will have the most impact on them:  wind and sun.  A hot, windy day would not be the day to start the move.  For the first excursion, pick a temperate day with no wind and even then, put your plants in a protected area in the shade.  You might leave them out for only a few hours.  After that, increase the exposure time each day, moving eventually to dappled morning sunlight, and then gradually to full morning sunlight.  Placing plants in full afternoon sun will be done toward the end of this process, as well as leaving them out overnight, but only when temperatures do not fall below 50°F.  Reducing water frequency to slow growth during hardening is advised.     

 

Transplanting Seedlings into the Garden

Like ‘hardening off’, choose your day and time carefully.  An ideal time would be the late afternoon or evening of an overcast day with little or no wind.  The worst day would be during a lengthy heat spell with lots of wind. 

Water your seedlings well before transplanting.  Then, dig a hole with the same depth at which the seedling is growing and a bit wider.  (Tomatoes, broccoli, cabbage, and cauliflower should be set deeper than they are growing.)  Mix in compost or a starter fertilizer at the bottom of the hole.  When removing the seedling from its container, treat the roots gently, trying not to tear them.  Also, if possible, handle the plant by its leaves rather than the stem.  After firming the soil around the plants, water gently including the leaves.  If there is concern about the effect of intense afternoon sun, you can choose to shade your seedlings by placing a board or piece of cardboard on the southwest side of the plants for a couple of days. 

Finally, the plants will likely experience little or no growth for up to several weeks, but do not get discouraged.  After that, the seedlings will have made themselves at home with roots that can support growth and your plants will begin to thrive. 

Congratulate yourself on the careful fostering of your little seedlings, and celebrate when they give back to you the abundance of their fruiting. 

May found our team tucking summer harvest seedlings into our beds and anxiously monitoring them to make sure they have everything they need to thrive.  Fertile soil is a must and the primary nutrients needed are N, (Nitrogen) P (Phosphorous), and K (Potassium).  All fertilizers sold are labeled with the content of these three nutrients as a percentage of the total nutrients supplied. 

NPK?

Nitrogen -  Of the three primary nutrients, California soil is most likely to be deficient in nitrogen.  This deficiency is increased with the rainy season when nitrogen can be leached from the soil.  Nitrogen is very important for photosynthesis; the most prominent symptom of nitrogen deficiency is chlorosis or yellowing of older leaves.

Phosphorus.  California soils usually contain phosphorous naturally, although highly-weathered soils can be deficient.  The symptoms of a phosphorous deficiency include stunted growth, purplish tint on leaves, and/or poor fruit or seed development. 

Potassium.  Additional potassium is usually not needed in California soils.  However, if deficient, plants can experience slow growth, browning with dieback of leaf edges and tips, weak stalks, and small fruit.    

 

NPK Testing

Prior to planting, a quick test of the NPK in your soil can alert you to the need for fertilizer.  At most nurseries, you will find simple testing kits for NPK that also test pH.  You will feel like a chemist as you shake water and tablets in test tubes and look at color charts to determine nutrient levels in your soil.  This process can be intimidating for some.  Many gardeners just watch their plants carefully and based on plant symptoms, they get a sense for what is needed.  So what choices do you have when you determine a nutrient is needed?

 

Fertilizer Types

Inorganic:  These fertilizers are composed of minerals and synthetic chemicals.  They are fast acting and low in cost.  But they contain salts and can leach and burn crops if applied incorrectly.  They do not have the ability to improve the soil.

Organic:  These are derived from plant or animal products.  They are bulkier and more costly than inorganic fertilizers and can have odors.  They are also slower to act. But besides adding nutrients, they work more naturally, improving the soil by decreasing density, which increases water filtration and the soil’s ability to hold nutrients. 

Manures:  These contain animal excrement, plant remains, or both.  They are a good organic fertilizer and they improve soil structure.  Many gardeners raise chickens and they get the benefit of chicken manure, the most concentrated NPK source of any type of manure. 

Fertilizer Use on a Certified Organic Farm

Because we are located on a certified organic farm, the Edibles Demonstration Garden (EDG) can only use organic fertilizers that in most cases are labeled OMRI Certified.  OMRI stands for the Organic Materials Review Institute and is a nonprofit organization that maintains lists of products that are FDA approved for use on certified organic farms. 

The EDG most often uses compost to improve our soil.  But compost alone does not provide the amount of NPK needed for heavy summer feeders like tomatoes.  We also use worm castings from our worm bins.  The approximate NPK percentages for worm castings are 5-5-3, which is much higher than compost.    

In the past few months, we have used fish emulsion (4-1-1) as a nitrogen boost for our artichoke plants and worm compost ‘tea’ for our seedlings that had yellowing older leaves.  We added blood meal (12-0-0) to our raspberries and a balanced fertilizer (7.5-5-7.5) to our fruit trees.  Artichokes, raspberries, and fruit trees are perennials.  Edible perennials often have specific fertilizer requirements especially in the spring so pay attention to their fertilizer needs also. 

As you tend to your garden this summer, look for symptoms of nutrient deficiencies.  Try to choose fertilizers that mimic the way nature provides nutrition for plants. The nutrient boost may take longer for you to see the benefits, but natural fertilizers pay off in the longer term.