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Archive for the ‘soil temperature’ Category

bean-seedlings-blogIf you are new to vegetable gardening, or even if you are an experienced gardener who has moved to a new climate, it may be hard to decide when to plant. It is easy to make a list of what you want in your garden, but when to put the seeds or transplants in the ground is the conundrum. There are many things to consider, but the most important is to know the average first and last frost dates for the area you are considering. If you have been keeping temperature records, that’s great! However, not many are that diligent. Not to worry, others have that information available for you. I am sure you could find it through the weather service or your local Cooperative Extension Service, but I’ve found that a quick way to get temperature and precipitation information is through plantmaps.com. The amount of annual rainfall is important, also.

Seed catalogs are a great help when deciding plant dates. At the beginning of each crop section in the catalog there is generally an information box that will guide you on planting. It might indicate that you should wait until after the last spring frost to plant a particular crop, but start the seeds about six weeks before you expect to put the transplants in the ground. So, count back six weeks from the date you have chosen to indicate your last expected frost and you know when to start the seeds in your house or in your coldframe. At the resource page of my website you can download a free Plant / Harvest Schedule to help you with your planning. You fill in your own crops and dates. p-h-sample-garden-w-cover-crops-blog

More confusing is when the planting information directs you to plant as soon as the soil can be worked. In that case I would look to what the soil temperature should be and the seed catalogs will indicate that.  FYI, the soil temperature is generally about 60° around the date of your last expected frost in the spring. Find more information at my post How Important is Soil Temperature. You can use a compost thermometer or a household kitchen thermometer to take the temperature of your soil several inches deep.

2017-catalogs-blogThe catalogs I have are Southern Exposure Seed Exchange (Virginia and local to me), Sow True Seed (North Carolina), Fedco (Maine), Johnny’s (Maine), High Mowing (Vermont), Seed Savers Exchange (Iowa), Territorial (Oregon), and Bountiful Gardens (California). I like to source my seeds as close to home as possible, but sometimes there are items or varieties that are available further away that I seek out.

It is good to have an overall reference book in your home library that you can consult for growing information for specific crops. In my early gardening days I was given a copy of How to Grow Vegetables and Fruits by the Organic Method edited by J.I. Rodale and the staff at Rodale Books. I still look to that when I have questions about a crop. In fact, I wore the binding out on my first copy and now use a copy I found in good condition at a used book store. A more recent book that is a terrific reference and one I turn to, also, is Pam Dawling’s Sustainable Market Farming. Pam is growing in the mid-Atlantic region but much of her information is applicable to a wider geographical area. You can find books specific to your region. Ira Wallace, of Southern Exposure Seed Exchange, authored The Timber Press Guide to Vegetable Gardening in the Southeast. Timber Press has published growing guides for seven regions of the U.S.

Here in Virginia, some crops, such as kale, can be planted in both the early spring and in the fall. It is too hot for these crops in mid-summer. My main crop of kale is planted in late summer for a fall and winter harvest. About March, as the days begin to warm up, overwintered kale will bolt, meaning it will send up a seed stalk that will flower and, if left alone, will produce seeds. Generally you would clear out those plants to make room for spring and summer crops, unless you plan on saving seeds. Seeds for my spring crop of kale will go into the coldframe sometime in late February, to be planted out in the garden when the seedlings are big enough—late March or early April.

A friend recently asked about growing in North Dakota, specifically at the Standing Rock Indian Reservation. She will be visiting there in late July and wanted gardening information. According to plantmaps.com, the last spring frost there is the first week of May and the first fall frost is late September.  I consulted The Old Farmer’s Almanac gardening calendar at http://www.almanac.com/gardening/planting-dates/states and found that when she gets there it will be time to plant lettuce, radish, spinach, and Swiss chard for a fall harvest.

In Zone 7 we can harvest lettuce until about Christmas and kale and collards all winter under a single layer row cover. The temperature rarely dips into the single digits, and then not for long. According to plantmaps.com, at Standing Rock in Zone 4b the temperature could go as low as minus 25°. Only the most cold hardy of greens could survive, and then with multiple layers of cover. It is important to research what varieties would do best under those conditions. For extended fall planting and harvesting times under rowcovers, consult Table 16 pages 205-207, in Eliot Coleman’s Four Season Harvest, 2nd edition. It helps you determine your planting times according to your first expected fall frost and, also, if you have one or more covers over your crops.

The summer nights are cooler in Standing Rock than they are here in Virginia. Besides warm nights, we have high humidity here. Our rainfall, about 44” annually, occurs fairly evenly throughout the year. Standing Rock gets only about 14.5” per year, mostly from April through October. Other places might get the bulk of their rainfall in the winter. More plays into your success in your garden than just knowing the frost dates, but that is a good place to begin to know your climate and when to plant. If you want to start keeping temperature and precipitation records for your garden, I have worksheets for that on the CD that comes with my DVD, Develop a Sustainable Vegetable Garden Plan. There is also a download code for these record sheets in my book, Grow a Sustainable Diet. Getting better acquainted with your garden this way will help you understand what Mother Nature is saying to you when you are there. Listen carefully.
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FEBRUARY 3, 1017 UPDATE: I was alerted that the map that appears on plantmaps.com is the USDA Hardiness map for 1990. The USDA updated their maps in 2012. Scroll to the bottom of that map and you will find a link to the 2012 map. There is also a link to the updated map in the right sidebar. Plantmaps.com has maps for countries other than the U.S., which should be helpful to many of my readers around the world.

 

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20" long compost thermometer with a 1 3/4" face

20″ long compost thermometer with a 1 3/4″ face

Spring is here and I know you are anxious to be in the garden. As soon as the temperatures begin to climb it is really tempting to get seeds in the ground. Before you take that step, however, I encourage you to make sure the ground is ready for your seeds. Of course, you will loosen the soil and add compost and, if necessary, organic fertilizers, but did you take the temperature of the soil?

Seeds are naturally programmed to germinate and grow within a certain range of temperatures. Within that range they will grow faster or slower, depending on their comfort zone. It has been my experience that just because it is the right time to plant on the calendar, it may not be the right time to plant according to the soil. The temperature of the soil is more important than the date on the calendar. When I was a market gardener I would be anxious to get sugar snap peas in the ground in early March. I would put in another planting two weeks later. If the weather had been too cool, the first planting may not come into production until the second planting did. I learned to pull back the leaf mulch that covered the bed over the winter and put down a sheet of plastic two weeks before planting the sugar snaps to warm the soil. If the weather has been too cool and wet there is the danger that the seeds will rot and not germinate at all. Peas, beans, and corn are most susceptible to this, which is why you might find those seeds for sale coated with fungicide. Steer clear of fungicide coated seeds and plant at the right time. Beans and corn like the soil to be 60° F (15.6 °C) and cowpeas would like it if you wait to plant until it warms to 65° F (18.3°C).

If you have mulch covering some of your garden beds, go out and stick your hand in the soil under the mulch and then put your hand in the soil in a bed without mulch. You will feel a noticeable difference in the temperature. During the winter an organic mulch such as leaves or straw does a good job of protecting the soil and providing habitat for the earthworms. However, when things begin to warm up in the spring the mulch will insulate the soil from the sun’s rays. Removing the mulch two weeks ahead of planting will help to warm the soil. I am not so much in a hurry these days, so I don’t use plastic to further warm the soil, but it is an option. With my system of cover cropping, when the cover crop is finished, it is naturally time to plant the next crop.

thermometer with a 5" stem and 1 1/4" face

thermometer with a 5″ stem and 1 1/4″ face

You can monitor the temperature of the soil with a thermometer or by sticking your hand in the ground. Even better, go barefoot. There’s nothing like the whole body experience. You might want to use a thermometer until you can gauge the temperature by touch. I use either a 20” long compost thermometer with a 1¾” face (top photo) or a thermometer with a 5” stem and 1¼” face that I bought at the grocery store. I keep the long thermometer stuck in the soil somewhere so I don’t lose it. Usually it is in my coldframe, where it is right now. The nice thing about the compost thermometer is that it is easy to read without bending over too much. The small thermometer has so many uses. It comes with a plastic sleeve that has a pocket clip –handy if you are going to be carrying it around. The one you see in the photo is the one I use to monitor the temperature in my solar food dryer. It sticks through a hole drilled for that purpose with just the gauge showing on the outside of the dryer. A small thermometer such as this can be used in the kitchen, which is why you will find it in the grocery store.

You can find a chart showing a list of crops and the minimum, optimum, optimum range, and maximum soil temperature conditions for each in How to Grow More Vegetables by John Jeavons. A chart I find interesting is Days to Appearance of Seedlings at Various Soil Temperatures from Seed Planted at ½” Depth, compiled by J.F. Harrington. You can find it with an Internet search. It shows the number of days it takes for each crop to germinate at different temperatures. For example, peas will take 36 days to germinate at a soil temperature of 41°F (5°C), 13 days at 50°F (10°C) and 9 days at 59°F (15°C). You can see how warming up the soil will contribute to an earlier crop.

tomato,pepper, and zinnia seedlings in the coldframe???????????????????????????????

coldframe seedlings–tomatoes, peppers, and zinnias

Peppers, on the other hand, are shown to take 25 days to germinate at 59°F, 12 days at 68°F (20°C) and 9 days at 77° F (25° C). If you plant pepper and tomato seeds at the same time, the tomatoes will germinate first—in 14 days at 59°F, 8 days at 68°, and 6 days at 77°. I start my seeds in my coldframes, which provide cooler temperatures than starting them in the house. I put tomato, pepper, and other seeds of warm weather crops in my coldframe during the last week of March. Since I save much of my own seeds, I am developing strains of each crop that will germinate in cooler soil. The healthy plants that I take out of the coldframe are the ones that have germinated and thrived in the cooler conditions. The peppers that I have been most successful with in the coldframe are Corno di Toro and Ruffled Hungarian.

By saving your own seeds, you can develop strains of your crops that will germinate and grow under the conditions that you want to work with. Experiment with planting times and conditions in your garden. I would advise, however, to only take chances with what you can afford to lose. If you go into it with that attitude, you won’t be disappointed.

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