The Modern Victory Garden

There are many of us who have limited space availability for food production gardening and yet still manage to produce a tremendous amount of our own food supply.   This post is part of a blog series devoted to exploring the many techniques available to optimize food production gardening. There are quite a few topics that relate to this pursuit - including (among others):

• Crop Selection
• Intensive Planting Practices
• Season Extension
• Soil Management & Fertility

Focusing on Crop Selection kicked off the blog series, which was then followed by a four-part exploration of Intensive Planting Practices - including the topics of Raised Beds, Closely Spaced Planting, Intercropping & Succession Planting, and Vertical Growing.   This week let’s talk about Season Extension.

Season extending is essentially the practice of using various tools and techniques to allow for a much earlier start and a much later ending to the growing season.   There are three primary reasons to go to the trouble and effort of extending the garden season:

1. It allows you to grow crops that require more growing days than your area would naturally provide;
2. It provides enough additional growing days that you can plant crops in succession that otherwise would not have sufficient time for the second crop to mature; and
3. It lets you harvest fresh greens and vegetables for much longer than the traditional growing season would allow – throughout the entire year for really cold hardy crops.

My own experience with season extending is that it is most efficient and effective if I work with nature rather than against her.   In addition, I think that you have to be able to accept that there will be losses periodically.   A wise gentleman once told me that if you are not occasionally losing some crops in the early spring and late fall – you are probably not living close enough to the edge on your season extending practices to be getting full value from it.      

Season extension generally uses various forms of protective covers or structures to increase soil and air temperature, protect plants from wind and frost, and reduce moisture loss.   Of these benefits, I believe the greatest value comes from the warming of the soil.   The Rodale Research Center has conducted experiments that show temperatures at the plant’s root zone is more important to growth than air temperature surrounding the leaves.   The ability to provide a warmer environment and soil comes from passive solar heating that is then (in some part) captured by a heat sink (dark soil surface or dark plastic mulch) that absorbs the solar heat more than a light or reflective surface would.   Some folks move beyond passive solar options and actually use a hot bed or greenhouse that has an energy consuming heat source.   While this certainly will yield good results, it is also fuel intensive and can be quite expensive.   For the purposes of getting optimal production and value out of our home vegetable and fruit gardens, I think it is impractical to consider regularly using anything but passive solar options.                                     

The real trick to using unheated season extension is to capture and hold as much solar heat as possible and to grow crops that are by nature already very tolerant of cold conditions.   Cold hardy crops like spinach, kale, corn salad (mache), root crops (beets, parsnips, carrots), brussel sprouts, green onions, leeks, certain cold hardy cabbages, and a variety of less common greens are all really good candidates to be grown late in the season or overwintered with protection.   Similarly in very early spring, you can use protective covers to thaw and warm up garden soil long before the last average frost for your area - so that you can get an extremely early start for hardy vegetables such as peas, onions, Chinese cabbage, lettuce, spinach and kale.   These vegetables will germinate and grow in relatively cool soil temperatures (at least 40 degrees or greater) and often have planting instructions to “sow as soon as you can work the soil”.   I mentioned in another recent blog post that I think there are two simple tools most gardeners should have in their garden shed – one is a PH meter, and the other was a good soil thermometer.  

During the early spring if you are going to push the start of the growing season you really need to be able to monitor the soil temperature to know when it is ready for planting up.   As noted before, the soil temperature is much more important to pay attention to than the ambient air temperature.   Soil temperature should be measured 1 to 3 inches below the surface of the soil and the best time to take the measurement is between noon and 3 pm.   Remember to shake the thermometer back down before you use it again.   If you place a season extending cover over a growing area it will take a while for the soil to warm (days), and it is important to measure the progress with your thermometer periodically so you know when you it is ready for planting up.    

There are many season extending protective covers that can be used ranging from a cloche, cold frame, grow tunnels (also known as portable hoop houses), full size hoop houses, or greenhouses.   Each of these examples of season extending protections provides the benefits previously described - with varying degrees of success.   In general (assuming an equivalent sunlight exposure), the larger the volume of air in the protected area and the more dark surface area available and/or insulating materials used – the greater the warmth will be for the growing area protected.         

I generally use three types of season protecting covers. The first is a simple plastic sheeting cover raised just enough off of the surface of the soil to provide solar heating of the soil for the purposes of warming up a seedbed for a very early planting.   The cover can be left in place after the germination has occurred until the plants get tall enough to push up close to it. Usually by that point the weather has continued to improve enough that they are safe anyway and ready to grow on without the protection of the cover.               

You may recognize my tomato ladders in the preceding picture being used as the support structure for the plastic cover - just laid on their side over the bed edging boards.                       

The second type of protective covers I regularly use are grow tunnels.   I use 10 foot sticks of electrician’s PVC conduit (connector end cut off) inserted into brackets placed on the edge my beds or directly pushed into the soil (inside of the bed edging) to create support hoops.   Over the support hoops I place clear plastic (4 or 6 mil) that you can purchase at any hardware store (usually in the painting supplies area).   I use inexpensive “A” or spring clamps to hold the plastic securely to the hoops.   They last an incredibly long time and make quick removal and access to the growing beds possible.   These same hoop tunnels can also be used during the summer growing season to hold protective bird netting over the grow beds.  This is useful to keep birds and other creatures out of the garden (like bunnies, cats, and dogs).   I use netting regularly to protect my beds from my dog who seems to walk through every newly seeded bed that exists unless protected in this manner!     

I generally use grow tunnels to either protect an overwintered crop (such as a large bed of spinach), protect newly planted seedlings during the early months of the growing season when weather is unstable and the plants are very young and tender, and to warm up large areas of growing bed for early crop starting.                

The third protective cover I regularly use is my unheated green house. During the late fall and winter months, I use it to grow cold hardy crops in large containers.   I generally grow mostly greens in the greenhouse because the larger air volume and greater surface area captures solar energy better and increases the odds of semi-hardy crops like swiss chard, Chinese cabbages, and lettuces of surviving.           

In the spring, I use the unheated greenhouse to grow on the semi-hardy crops that I started under the grow lights very early in the year.   This allows me to move them out of the seed starting area - making room for the next big round of seed starting (usually the summer crops of tomatoes and peppers etc) but protects them from the erratic and unpredictable very early spring weather conditions.             

Using season extension techniques can increase your garden’s production but as much as 25% just by adding 1 to 2 months of growing time at each end of the growing season.   Do you use season extending tools in your garden and if so, what kinds?