What is the advantage of keeping the bottom of the cuttings warm? As I wrote in Part 1: The bottom of the stems should be kept warm because roots tend to develop quicker.
68 to 70 F is a safe range to shoot for.
Higher rooting medium temperature can be beneficial, but because the sun will raise the mediums temperature anyway, shoot for the 68 to 70 F range and you will be less likely to cook the cuttings.
If you try for a higher medium temperature and the sun warms the soil even higher, the cuttings will surely suffer.
So how do we go about keeping the bottoms of the cuttings warm? There are a few ways to accomplish this, but the easiest and less expensive way is to use soil warming cables.
Soil warming cables do exactly that; they warm up the rooting medium to help the cuttings form roots.
Cables can be purchased in various lengths to accommodate different misting bed configurations.
The better soil warming cables will tell you how many square feet the cable will cover.
Using a misting bed dimension of 4 foot wide by 10 feet long (4' x 10'=40'), you would need a soil warming cable capable of warming 40 square feet.
Which type of soil warming cable should you use? There are basically two types of soil warming cables:
The built in thermostat is designed to activate at a preset temperature, usually around 74° F.
If the soil temperature falls below the 74° set point, the cable will activate and begin to warm the soil.
The cable with the separate thermostat can be set for a particular temperature usually between 40° and 100° F.
This gives you more control over the temperature of your soil.
Because every plant differs in terms of rooting requirements, the biggest benefit of the adjustable thermostat is the ability to "dial in" the optimal temperature for the plant you are rooting.
For instance, Forsythia tend to root better with soil temperatures around 86° F, where other plants root well with lower temperatures.
Being able to increase or decrease the soil temperature to suit a specific plant can greatly increase your success.
How do you install the cable? It is actually quite simple, but first you need to prepare the misting bed for the soil warming cables and thermostat.
The rigid foam insulation comes in 4'x8' sheets and can be cut to size using a knife or handsaw.
Attach the pieces to the inside of the bed with a few screws.
Once the bed is filled, the rooting media will help hold it against the sides of the bed.
If you decide to use the insulation, be sure to install it before the layer of vermiculite, cable, wire, and remaining rooting media.
Install the thermostat in a location that has an outlet available and where the end the the soil warming cable will reach it once the cable is installed in the bed.
Some thermostats are designed to be used outdoors with no protection and others are not designed for wet locations and may need protection from the elements.
Be sure to choose the correct one for your location.
It is also advisable and in some cases required by law to use a Ground Fault Interrupting circuit for all outside electrical outlets.
Check with your local code office or an electrician for clarification.
That's it! Simple now wasn't it? HINT: Until you get a good feel as to which plants like really warm soil, a good temperature to start with is 68-70° F.
68 to 70 F is a safe range to shoot for.
Higher rooting medium temperature can be beneficial, but because the sun will raise the mediums temperature anyway, shoot for the 68 to 70 F range and you will be less likely to cook the cuttings.
If you try for a higher medium temperature and the sun warms the soil even higher, the cuttings will surely suffer.
So how do we go about keeping the bottoms of the cuttings warm? There are a few ways to accomplish this, but the easiest and less expensive way is to use soil warming cables.
Soil warming cables do exactly that; they warm up the rooting medium to help the cuttings form roots.
Cables can be purchased in various lengths to accommodate different misting bed configurations.
The better soil warming cables will tell you how many square feet the cable will cover.
Using a misting bed dimension of 4 foot wide by 10 feet long (4' x 10'=40'), you would need a soil warming cable capable of warming 40 square feet.
Which type of soil warming cable should you use? There are basically two types of soil warming cables:
- One that utilizes a built in thermostat
- One that requires a separate thermostat to be purchased
The built in thermostat is designed to activate at a preset temperature, usually around 74° F.
If the soil temperature falls below the 74° set point, the cable will activate and begin to warm the soil.
The cable with the separate thermostat can be set for a particular temperature usually between 40° and 100° F.
This gives you more control over the temperature of your soil.
Because every plant differs in terms of rooting requirements, the biggest benefit of the adjustable thermostat is the ability to "dial in" the optimal temperature for the plant you are rooting.
For instance, Forsythia tend to root better with soil temperatures around 86° F, where other plants root well with lower temperatures.
Being able to increase or decrease the soil temperature to suit a specific plant can greatly increase your success.
How do you install the cable? It is actually quite simple, but first you need to prepare the misting bed for the soil warming cables and thermostat.
- Before you add your rooting media (sand, peat/perlite, etc), place a layer of vermiculite at least 2" deep at the very bottom of the bed and level it out.
The vermiculite will insulate the bottom of the bed and help retain the heat and funnel it upward to the bottom of the cuttings. - Lay your cable on top of this layer, being sure that the end that will plug in, will be above the surface of the rooting media.
Be sure to not let the cable touch itself at any point or it may overheat and burn out. - Next, add a 1" layer of your rooting media, ie; sand or peat/perlite.
On top of this layer of rooting media, place a piece of wire mesh to ensure you do not mistakenly dig into the cable when digging out your cuttings. - Now fill the remaining space in the bed with your rooting media.
The rigid foam insulation comes in 4'x8' sheets and can be cut to size using a knife or handsaw.
Attach the pieces to the inside of the bed with a few screws.
Once the bed is filled, the rooting media will help hold it against the sides of the bed.
If you decide to use the insulation, be sure to install it before the layer of vermiculite, cable, wire, and remaining rooting media.
Install the thermostat in a location that has an outlet available and where the end the the soil warming cable will reach it once the cable is installed in the bed.
Some thermostats are designed to be used outdoors with no protection and others are not designed for wet locations and may need protection from the elements.
Be sure to choose the correct one for your location.
It is also advisable and in some cases required by law to use a Ground Fault Interrupting circuit for all outside electrical outlets.
Check with your local code office or an electrician for clarification.
That's it! Simple now wasn't it? HINT: Until you get a good feel as to which plants like really warm soil, a good temperature to start with is 68-70° F.