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Posts Tagged ‘soil temperature’

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.

Homeplace Earth

 

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williams pride in full bloom 2013 - closeup-BLOG

Williams Pride apple blossoms

What you see in the photo is blossoms on a Williams Pride apple tree. The data stored automatically from my digital camera says that photo was taken on April 16, 2013. What a handy thing that is for the camera to record that information! I surely didn’t at the time. What difference does it make that I know when that happened? Knowing when the bushes and trees in your yard bloom, drop petals, and whatever else they do, helps you to know when the time is right for planting your vegetable crops without looking at the calendar. The study of recurring plant and animal life cycles and their relationship to weather is called phenology. By studying these things, we can learn how our climate is changing from year to year and, more specifically, we can know how things are doing this year. Are things blooming later than usual? In that case you wouldn’t want to be too anxious and plant your vegetable crops earlier than normal. My friends, Pam Dawling and Ira Wallace, keep phenology records of what is happening at their farms in Louisa County, Virginia. In her book, Sustainable Market Farming, Pam says that falling apple blossoms are said to be a phenological sign that conditions are good for transplanting celery and celeriac. She goes on to say that the time to plant is after the last frost and the weather has settled. For planning purposes, I use April 26 as the date for my last expected frost. I imagine those petals would have been dropping by then. You can read more about what Pam has to say about phenology and even see the chart she keeps for the gardens at Twin Oaks Community at http://sustainablemarketfarming.com/tag/phenology/. Ira mentions phenological signs in her book Vegetable Gardening in the Southeast. In this era of climate change, the date on the calendar of when to plant things will gradually shift, but nature will already be on top of it.

The temperature of the soil is also an indicator of when to plant. In fact, soil temperature has a lot to do with the phenological signs I just mentioned. Just because the air temperature has warmed up, doesn’t mean the soil is ready for seeds and plants. Over the years I’ve noticed that we have a warm week in the first half of April. The temperature might even soar into the 80’s. I’ve also noticed that in the next couple weeks after that, April will deliver cold temperatures before the weather settles. I taught at a community college and no matter how much I talked about expected last frost dates (and that it wasn’t until late in April in our area), some of my students would plant warm weather crops during those early warm days. A new farmer once asked me when I planted summer squash and snap beans. When I replied after April 26, he said he got that same answer from a neighbor. It was that warm spell in early April and he had just planted his warm weather crops. He thought I was being too cautious. I advised him to only plant early what he was prepared to lose and to plant his main crop when the soil was warmer.  Of course, many farmers have high tunnels and use row covers now to get a head start on planting. They are warming the soil to prepare the right conditions for the seeds and transplants.

compost thermometer in kale bed

compost thermometer in kale bed

You can check the soil temperature by putting the probe of a thermometer a few inches into the soil. I use a compost thermometer for that. It has a long stem that serves two purposes. I can read it without bending down so far and I can find it when I need it. I often leave it in a garden bed or a coldframe so I know where it is. I can readily know the temperature in that spot and pick it up to move it to a new location. I have a thermometer I keep in my kitchen that I bought from a cheesemaking supplier. I use it when I make yogurt, but it would do to check my soil. You can buy an inexpensive (about $7) thermometer at the grocery store. Those thermometers even come with a plastic sleeve to protect the stem. That would do fine to check your soil temperature. As long as you are keeping records of phenological signs, you might record the soil temperature at the same time. Keep in mind that it will vary if you are checking it at different times of the day or in different locations, so be consistent. Nancy Bubel’s book The New Seed Starters Handbook contains helpful charts on Soil Temperature Conditions for Vegetable Seed Germination, the Number of Days for Vegetable Seeds to Emerge at Different Temperatures, and the Percentage of Normal Vegetable Seedlings Produced at Different Temperatures.

ladybug on cowpea plant

ladybug on cowpea plant

Knowing what the insects and birds are doing should be part of your phenological records. If you haven’t gotten your record keeping set up before things start blooming and insects and birds start appearing, take photos and let your camera record the date for you, if your camera does that. If insects are on a plant, by taking the photo, you will have a visual record of the insect and of plants they like, whether they are beneficial insects or harmful ones. This photo shows a ladybug on a cowpea plant. I’ve found other beneficials attracted to the cowpeas. As I write this, we are in the grip of weather colder than normal, even for winter here. Before it hit, someone told me she knew a weather event was coming because she saw bluebirds at her bird feeder. Since bluebirds eat insects, they were usually not visitors to her feeder.

At the very least, even if you never record any of these things, start to notice them. Keep your eyes and ears open and you will become more in tune to where you are and what is going on around you. There is a whole other world available to you, right in your garden. All you have to do is take the time to noticeHomeplace Earth

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