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Monthly Planting Guidelines

March

This calendar’s monthly planting guidelines are based on USDA zone 9, but they are adaptable to most zones. To find your zone, go to the National Gardening Association’s website. If your zone is 7, 8, or 9, you can safely use this guide. If your zone is 4, 5, or 6, then add a month before beginning your spring tasks and start your fall tasks a month earlier. If your zone is 10 or 11, subtract a month to your spring tasks. Your fall and winter tasks should remain the same as the original guide if you are in zones 10 or 11. These are all general guidelines. Your specific microclimate, which depends on distance to a large body of water (like gigantic lakes or oceans) and elevation, will make your zone fluctuate. Consult your local county extension office to get more detailed zone and planting guide information.

Tasks for March:

  • Amend planting area
  • Install drip irrigation or check on existing irrigation health
  • Add plastic to top of beds
  • Pot up seedlings

Amend planting areas:+

March is the major gearing-up time for your summer garden. Now is the time to amend your soil in preparation for planting. There are as many ways to amend your soil as there are gardeners in the world. This “recipe,” however, is good for a 50-square-foot surface area of growing space.
First, remove rocks, weeds, and any large pieces of wood mulch or twigs. Spread the following mixture evenly on top of the 50-square-foot area:

  • 1 pound mustard meal
  • 1 quart all-purpose dry organic fertilizer (something like 4-6-3 or 4-4-4)
  • 1 quart 100 percent worm castings
  • 1 full wheelbarrow of homemade compost or one two-cubic-foot bag of compost

Let’s talk about each of these ingredients:

Mustard meal

As many of you may know, tomatoes are prone to disease. Agricultural scientists are constantly doing research on various things to increase tomatoes’ health, including fertilizers, fumigants, hybridization, pesticides, inoculants, sprays, etc. So when something is proven to be beneficial to tomatoes, it’s time to listen up.

Mustard meal is a dried and pelleted version of Pacific Gold Mustard, a crop often used in cover crop mixes. Both the cover crop and the pelleted version have been shown to help reduce harmful populations of nematodes in the soil. These nematodes make breaks and galls in tomato roots, creating entrances for soil-borne diseases, such as Verticillium wilt, to more easily infiltrate the tomato. It’s smart to not only use a winter cover crop of the Pacific Gold Mustard but also to dig the pelleted mustard meal into your garden beds as well.

Use one pound per 50 square feet of garden space. It MUST go into the bed at least two weeks before planting so it has a chance to dissipate, do its work, and become less “hot and spicy” for your seedlings. So amend your beds in March for an April or May planting date. If you aren’t planting until May, then you can do this chore in April.

All-purpose organic fertilizer

Add four cups (or one quart) of all-purpose organic dry fertilizer to every 50 square feet of growing space. The term “all-purpose” means that all three macronutrients—nitrogen, phosphorus, and potassium—are represented in somewhat equal amounts. When the phosphorus number is a bit higher than the other two numbers, though, additional blossoms can occur. And more blossoms mean more fruit, usually (can’t get a fruit without a flower first). All good nurseries will sell an all-purpose dry organic fertilizer.

Worm castings

Worm castings are organic, high-quality, high-potency fertilizer for your garden vegetables. If you’re lucky and get to create your own or source it from a reliable, local outfit, it should still have worm eggs in it. These are beneficial worms, usually red worms, that will dig through your soil, devouring organic matter and excreting fantastic poo, or “castings.” Making a liquid elixir of it and spraying it on your tomato plants every week works very well. That subject is more thoroughly covered in the June calendar guide.

Add four cups or one quart of 100 percent worm castings for every 50 square feet of growing space. Pure worm castings tend to be pricey and come in small packages. If you see a large bag (like a huge soil bag) for less than $15, double-check the ingredient list—you’ll find most of that bag to be filler.

Compost

The best compost should be your own homemade compost. However, if you don’t have enough (and really, who does?), you’ll need to purchase some.

Compost varies greatly in quality. If a bag at your nursery says “soil conditioner,” it’s probably not compost. Similarly, don’t buy pure manures, such as steer or chicken manure. These tend to be too “hot” (not fully decomposed) and too high in nitrogen for use in your vegetable garden.

Good compost should be made up of as many different ingredients as possible—that’s why homemade is best. However, store-bought can be good too, as long as it smells good when you open the bag, doesn’t attract gnats or flies, and isn’t hot to the touch when you insert your hand into it. Beware of “free” compost, as it can also not be decomposed enough or it may contain harmful additions. Any compost using redwood, walnut, pressure-treated lumber, invasive tree species, herbicide-sprayed materials, and pernicious weeds will harm your garden, so it’s best to know your source and their ingredients.

Evenly spread a full, large wheelbarrow of homemade compost or one large two-cubic-foot bags of good, organic store-bought compost over the bed.

Once you’ve got the four ingredients sprinkled somewhat evenly over the surface of the bed, dig them in as deeply as you can using a spade fork or a shovel, breaking up large chunks of subsoil as you go. Try to get the new additives at least a foot under the existing soil. The deeper, the better. Remove any rocks, large pieces of roots leftover from last season, twigs, and other large debris. Now is also a good time to add additional soil if you have raised beds and your beds have compressed over time. For example, for lumber-sided raised beds, top them off, giving maximum root space.

After you’ve thoroughly mixed the amendments in with your existing soil, rake the surface smooth. You can place your irrigation lines down on the bed if you have them and water the soil well if it’s dry. The mustard meal needs to be wet to begin its assimilation into the soil. If you don’t have irrigation lines, then hand-water the newly amended areas until the soil is saturated to the depth that you were able to amend. Keep checking the soil with a trowel (a small hand shovel) to ensure you’ve watered it enough. If significant rain is in the immediate forecast, then no need to water. Note that you’ll need at least an inch of rain to saturate the soil properly to get the mustard meal going.

If you live in a drier climate or aren’t experiencing much rainfall, then ensure the beds remain moist during the weeks leading up to your planting date. Earthworms tend to leave areas of excessive dryness and excessive wetness, so keep a good moisture content in your beds. How often to water will depend on your soil tilth (clay, loam, or sand) and the supplemental moisture your climate naturally brings. You don’t want the beds constantly soaked, but you don’t want them too dry, either.

Install or upgrade drip irrigation

March is also a good time to install a new drip irrigation or troubleshoot and repair your existing irrigation system. It’s easy to install from a nearby spigot. Professional-grade systems purchased from a local sprinkler and pipe store will last longer and offer more versatility than homeowner-grade systems. Also, be sure to install a shut-off valve for each bed.

Schedules and timers for your garden aren’t always recommended because of the many variables that alter watering needs: plant type, soil tilth, climate, mulch, age of plant, daily temperature, etc. If you want to use a timer, use a “countdown” timer, similar to an egg timer in the kitchen: You manually turn the water on using the timer and set it for a number of minutes, such as 30 minutes, and the timer automatically shuts off the water. It’s best practice to check your garden daily and see what needs watering. Then turn on the countdown timer for each area that needs watering.

If you already have irrigation installed, March is a good month to troubleshoot it. Turn it on and see if it’s functioning properly. If not, you may need to order replacement parts or visit your local sprinkler store to ensure you’ve got the proper parts to fix it.

Add plastic to the tops of beds

Tomatoes (and many other veggies) benefit greatly from being grown on top of plastic. March is a great month to do this because it aids in keeping weeds down and warms the soil before planting. You can purchase clear, greenhouse-grade (UV-resistant) plastic online by the foot. After planting, plastic-covered beds help in myriad ways: They keep soil warmer, virtually eliminate weeds, reduce fruit rot by preventing the fruit from touching the soil, and reduce water usage.

After bed amending and troubleshooting or installing new irrigation, cover the soil with the plastic so it’s in direct contact with it, making sure to cover the irrigation lines as well. If you have lumber-sided beds, you can staple (using a heavy-duty stapler) the perimeter of the plastic on top of the lumber. Turn the plastic several times on top of itself along the top edge of the wood before stapling; this will make it less likely to pull away from the staples. Ensuring that your beds are full to the top of the lumber is also an important part of being able to staple down the plastic flat on top of the bed.

The only downside to using plastic is that, at some point, when the weather turns consistently hot (July 1, give or take), the plastic will super-cook the roots. At that point, adding a thick layer of straw or mulch on top of the plastic will cool down the surface, with the plastic still doing its part to prevent weeds and recycle water evaporation.

Plastic-covered beds need about half the watering that non-covered beds require. Faster growth seems to occur in the early part of the season because the plastic is warming the soil, something young tomato plants are looking for in April and May.

Potting up seedlings

If you’re growing your own seedlings and you started three or four weeks previously, then you’re probably on track to pot them up. Ensure you have larger containers on hand, something like a three- or four-inch round or square pot, good organic potting soil, and more labels.

March Newsletter

Gently remove the seedlings from their sowing tray, separate by the roots into individuals, and pot them up one to a new pot. They need their own growing space at this point. Sink them deeper into the new soil about halfway up their stem or even deeper. Tomatoes love to be planted deeper and deeper every time you pot them up or transplant them out to the garden. This is because the tiny little hairs on the tomato stem will turn into roots when contacting the soil. These new roots create a stronger, more robust tomato that will grow faster into the summer months.

Your tomato seedlings should be getting fresh air and direct outdoor sun every day and be brought into a heated structure at night. The exception is if your outdoor temperature is less than 45 degrees Fahrenheit during the day or if it’s raining hard. If the latter two situations exist, bring them in for the day and put them right up against a south-facing window. Even if it’s overcast, there should be some UV coming through the window. This is not a good environment for them for more than a day or two, however, due to low light and restricted airflow.

If you live in Zones 1–5 and are experiencing a cold March (where daytime temps are consistently below 45 degrees), you can build an indoor grow room of sorts using four-foot-long fluorescent shop lights hung from lightweight chains on an industrial rack. Place your seedling trays under the lights such that only an inch of space exists between the top of the leaves and the tube lighting. If you use one warm bulb and one cool bulb, you’ll be mimicking more natural light. This indoor racking system requires a small fan blowing on the tomatoes at least eight hours every 24 hours, or else you’ll experience damping off and weak plants.

If you’re growing in warmer climates—Zones 6 and above—then you’ll be putting your tomato babies outdoors in direct sunlight every day (light rain is okay, as is an overcast sky) and then bringing them inside a structure each night. This natural daylight and air movement will go a long way toward growing healthy and happy tomatoes. You also will not need to harden them off (see April’s to-do list) before planting.

Don’t forget to fertilize your tomato seedlings. Fresh, new potting soil has fertilizers added to it. However, this fertilizer is generally only going to feed for about three or four weeks until the fertilizers get taken up by the plants or drained by watering. At the three- or four-week mark, after potting up or direct sowing into their initial trays, fertilize your seedlings once every few days with a half-strength solution of an all-purpose, organic liquid fertilizer. Try worm casting tea: The recipe is two handfuls of pure castings to a five-gallon bucket of water. Let it sit for two days to “steep,” stirring every so often. Then strain the mixture using cheesecloth or floating row cover, and you’ll have some very good fertilizer (this can be used in full strength) for your tomato babies and anything else currently growing in your garden. This solution is only going to last a few days, so if you don’t have a lot to fertilize, mix up a smaller batch. If you find yourself with extra worm casting tea, simply put it on some houseplants, outdoor perennials, annuals, or any plant material—they all love it.

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