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Let's Grow a Garden! Part 1: Temperature, a key factor for growing our food

Author: Noelymar Gonzalez


Winter is almost over and that means we can start preparing to grow our own food in our garden! Growing our food is a great opportunity for learning and having fun, and also for developing food sovereignty and security for ourselves, our loved ones and the community. However, have you wondered why we have to wait until the spring or summer to grow our food? Why do we need to wait until it is warmer to grow plants? What effects do temperature have in our crops? Let’s find out!


Photo by Jarosław Kwoczała on Unsplash

Temperature is an important factor that impacts plant’s growth. Plants, especially the ones that we grow in a garden like vegetables, fruits and herbs, generally prefer to grow in temperatures starting from 40 to 85 F. In extreme temperatures like in freezing weather in the winter or extreme heat in the summer, most of our garden plants become affected to the level that we can observe significant changes. Here, we’ll discuss in general terms what happens to plants when the temperatures are not favorable for their development.



What happens when it’s too cold?


1. Dormancy


Have you noticed that some plants resist the winter, while others don’t? Have you seen that the plants that resist the cold climate, perennials, often drop all their leaves when it starts getting cold in the fall? These things happen because some plants, and seeds as well, can enter a stage of dormancy when the weather gets too cold. In fact, there are two types of dormancy: 1) eco- and 2) endo- dormancy.

Photo by Courtney Read on Unsplash

Endo-dormancy is a deeper stage of dormancy at the cell level and this is triggered by plant hormones when the plant senses climatic changes like decreased light and temperatures. In response to these signals, plants slow and/or stop their growth and their metabolic activity, like photosynthesis, and drop their leaves. When the plants are too cold and pass endo-dormancy, they can go under eco-dormancy. Eco-dormancy happens when the plant is ready to grow or become active again, but the environmental conditions do not allow for the plant to grow. The same can happen to seeds, but seeds can go into dormancy due to cold weather and also due to lack of water even if the temperature is favorable.


Here is a very general illustration on how plant hormones influence growth and development in perennial plants and seeds during different stages:



2. Low Temperature Plant Sensitivity


Cold weather, especially freezing weather, can harm many non-resistant plants like some annual vegetables or fruits. This happens because very cold weather can form small ice particles that harm or break plant’s cell membranes, provoking cell death and consequentially, plant death. In addition to cell breakage due to ice, plant cells can accumulate too many salts which eventually causes plant dehydration.



3. What happens when the winter is over?


Photo by Markus Spiske on Unsplash

When the winter is over, plants can wake up from dormancy, thanks to hormones like gibberellin, auxin and cytokinins messaging and continue their activity. In the case of seeds, they’ll be able to germinate well in warmer weather with the help of water. Different crops require specific ranges of temperatures to germinate and/or grow.


4. What happens when it's too hot?


When the weather is too hot, many plants can also face damage. For instance, some plants can experience decreased growth, water stress, and dehydration when there is also lack of sufficient water or there is too much water evaporation due to heat. These problems happen because intense heat can cause significant decreases in plant photosynthesis rates and transpiration efficiency. When plants don’t do sufficient photosynthesis, this can decrease the plant cells enzymes production (like Rubisco) and also synthesis of ATP (adenosine triphosphate) production. The ATP is needed to produce energy and carry out activities in the cell (plants need this to live). Intense heat can therefore also impact crop productivity, decreasing yields and fruit or vegetable size and quality.





Now, let’s start planning and preparing our garden!


Now that the Winter is almost over and we’ll get appropriate temperatures for growing plants, let’s plan our garden and start some preparations.


1. Think about what kind of vegetables, fruits and/or herbs you would like to eat but that you are also able to maintain. Gardens take time, work and resources. Some plants require more care than others. For instance, tomatoes are more delicate and require more work than a herb like oregano. Also, think about what resources you have available. For instance, do you have good lighting? Do you have the required space for the types of plants you want to grow? Do you have easy access to water, pest control tools, or fertilizers?



2. Search for a local gardening guide that contains all the details on what and when crops grow best in the region. This will help you plan when to start germinating and transplanting. Cooperative Extension websites are a great source to find this type of information.

Here’s an example of a gardening guide:

Here's the link: http://sacmg.ucanr.edu/files/117117.pdf

3. Following your local gardening guide recommendations, start seed germination of your selected plants indoors until the climate gets warmer. Most annual plants prefer temperatures above 40 F to grow healthy. In the meanwhile, you can keep your plants and seedlings warm in a place inside. Seeds only need water and favorable temperature to germinate. Sow your seeds in a depth around 1.2 cm or 0.5 inches in the soil, cover them slightly if preferred, and gently add water. Some seeds take longer to germinate than others. Be careful to not over water the seeds, this might promote fungal diseases. The soil should be moist but not completely saturated.


Photo by Markus Spiske on Unsplash

4. After your seeds sprout, make sure to provide sufficient light. This light can be artificial (grow lights) or natural. Also, make sure to provide sufficient but not excess water. Using a spray bottle is a safe way for adding moisture to seedlings during the week. Like we mentioned before, make sure the soil is humid but not completely saturated.

Photo by Cathy VanHeest on Unsplash


To learn more, stay tuned for more upcoming gardening content this year! Let us know if you have any questions you'd like us to discuss.



Resources:


Irmak, S. (2019, July 22). Impacts of extreme heat stress and increased soil temperature on plant growth and development. Retrieved February 21, 2021, from https://cropwatch.unl.edu/2016/impacts-extreme-heat-stress-and-increased-soil-temperature-plant-growth-and-development


Longstroth, M., & Michigan State University Extension. (2018, October 02). Winter dormancy and chilling in woody plants. Retrieved February 21, 2021, from https://www.canr.msu.edu/news/winter_dormancy_and_chilling_in_woody_plants

Rohde, A., & Bhalerao, R. (2007, April 09). Plant dormancy in the perennial context. Retrieved February 21, 2021, from https://www.sciencedirect.com/science/article/pii/S1360138507000830

Seth Nagy. N.C. Cooperative Extension. (2015, February 17). Freezing weather and why it Harms Plants. Retrieved February 21, 2021, from https://caldwell.ces.ncsu.edu/2015/02/freezing-weather-and-why-it-harms-plants/

UNH Cooperative Extension. (n.d.). Dormancy: A key to winter survival. Retrieved February 21, 2021, from https://extension.unh.edu/blog/dormancy-key-winter-survival

University of California, Agriculture and Natural Resources. Cooperative Extension Sacramento County. Sacramento Vegetable Planting Schedule. http://sacmg.ucanr.edu/files/117117.pdf







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