Growing Vegetables From Seed
When planning a home garden you want to have fresh vegetables for as long as possible. You certainly don’t want everything to be ready at the same time but you also don’t want to have to wait for months before seeing any fresh organic vegetables on the table. So a large part of growing vegetables is to know when a particular vegetable will be ready to pick. So how can we tell?
This is actually not such an easy thing to do. There are two main guides that you can use; the simplest is Days to Harvest and the second is Growing Degree Days.
Days to Harvest Growing Vegetables
This is the simplest indicator. Look at these Blue Lake 274 Heirloom Bush Beans and you will see ‘58 days’ at the beginning of the description. Almost all seeds will list this. For vegetable seeds you start inside, or in a seed bed, and then transplant, these days begin when you do the transplanting. For seeds that are sown directly – Cosmic Purple carrots for example – the days begin when the seedlings emerge from the ground.
However you shouldn’t write ‘bush beans dinner party’ on your calendar just yet! These days are an approximation based on an average growing season in an average growing area. If your home garden is in a warm zone, the time will be shorter. If there is an unusually cold growing season, the time will be longer.
Growing Degree Days
For greater accuracy, the concept of Growing Degree Days was developed. They are also sometimes called Heat Units.
Growth of crops is mostly controlled by temperature. You can fertilize and water, but if the weather is cold plants just won’t grow. So every warm day plants grow a little. On very warm days they grow more than on cooler days.
So meteorologists look at the temperatures each day and they do this:
Growing Degree Days = (maximum temperature for the day + minimum temperature for the day) divided by two, minus a base temperature.
Or as an equation: GDD = (Tmax +Tmin)/2 – Tbase
The base temperature varies a little for different crops, but for corn it is 50oF, which is usually taken as a general figure when growing vegetables.
As an example, take a day where it goes up to 80o and then down to 65o at night. There would be 22.5 GDD for that day. For a more detailed discussion you can go here.
GDD is also used for insect control, to determine when a particular pest might appear, since insects grow faster or slower depending on daily temperatures. This site will link you to various resources for insect control using this method. This is especially useful for organic gardening.
The easiest way to keep track in your home garden is to download an app that will give you real-time data for the exact location of your home garden. You can also get a prediction for your zip code area between any two dates that will show the average GDD forecast and help you plan your planting times.
At this time, GDD amounts are available mostly for farm crops, but with the growth of organic farming figures for growing vegetables are becoming more available. The best plan is to keep your own records for your crops, so that each year you will get better at predicting exactly when you home garden will give you organic, GMO-free produce for the kitchen.