March Gardening Tips from CSU Extension

March is the start of many gardeners' seasons, particularly if you’re starting a new garden, improving it, starting seeds, or even planting early season crops. Regardless of how involved you are in the garden; March is a great time to make plans for the season coming up.

If you’ve had a soil test and your nutrients and/or organic levels are below 3-5% it may be prudent to amend with compost. The type of compost will influence your choice for amendment type. A manure-based compost will be higher in nutrients such as nitrogen, phosphorous, potassium etc. These, in excess in a soil, are also called salts. Plant-based compost will be lower in salts. You can amend more of the plant-based composts than the manure-based, levels will depend on need. See the chart below for approximate amendment values, reduce if your soil test shows higher salts or organic material. Incorporate compost into at least the top 6-8” of the soil, or crack into the soil with a broadfork if practicing limited tilling in your garden. If your organic material levels are over 5% it’s ok and even encouraged to take a year (or more!) off from amending your beds. More gardens are likely over-amended than under-amended. 

March is the ideal month to get your seed starting setup put together. Seed starting can be very basic (seed starting soil, water, container) or more elaborate for a better guarantee of success. To ensure the best start for your seeds you should seek out: sterile seed starting soil, good quality seeds, a heat mat, supplemental light, and containers that can help increase ambient humidity. Most seeds that can be started early will tell you how early to start. For example, tomatoes need to be started 6-8 weeks before you plan to transplant in the soil. Be aware not to start too early as larger seedlings can be harder to transplant. 

Sterile media – important to eliminate seedling death from damping off, a common fungal pathogen present in soil 

Quality seeds – caa photo of a seed starter trayn be saved from good local sources (your local seed library) or purchased from commercial retailers. Be aware that there are currently no GMO products available to home sales, so don’t worry about sourcing GMO free seed, they all are. 

Heat mat – many seeds germinate OK at room temperature, but much better with an extra nudge. Peppers, for example, can take up to 4 weeks to germinate at low temperatures but may be as few as 2 weeks at 75-80 degrees F. 

cats on a heat matSupplemental light – LED lights reign supreme now for successful supplemental light, but if a new light is beyond your budget you can combine a cool and warm ballast in a traditional shop light. Just be sure to keep the light close to your young plants. 

Seed starting containers – can be repurposed or purchased. Low and flat containers are often the most ideal, especially those that have a lid or top. Repurposed salad bins can be a great way to go, or seed starting flats. Be sure to have some way to check moisture at the bottom or encourage drainage (see the algal growth that can happen with a little too much moisture below!). 

Timer – timers can ensure that you have good amounts of light (14-16 hours is great!) without having to remember to turn lights on/off. Heat mats should stay on 24 hours.

Check out seed starting on Grow & Give for a more in-depth discussion:  https://growgive.extension.colostate.edu/grow/general-gardening-info/ 

If you have specific questions be sure to reach out to your local county Extension office. 

Happy Gardening!