March is the beginning of our outdoor gardening season. If you started cool weather crops indoors in February, you can begin transplanting into the outdoor garden in the middle of March. Alternatively, garden centers will begin selling transplants of cabbage family crops and lettuces to be planted on the same schedule. Lots of plants can be direct seeded into the ground as well.
Fruit growers should aim to get pruning done early in the month before serious new growth starts. It is also time to fertilize and plant bramble fruits and blueberries.
Let’s review some tips for getting things going.
Manage Your Soil for Best Growing Results
If you haven’t had a soil test for three years or more, consider a new test. They are a valuable tool for maintaining optimum soil fertility and pH levels. Soil sampling kits and instructions are available at your local Virginia Cooperative Extension office. In Charlottesville/Albemarle, test kits are available in marked plastic bins at the Albemarle County Extension Office off 5th Street Extended or at the Stagecoach Road building entrance. Be sure to take boxes and the appropriate instruction sheet for home gardeners versus commercial growers. Samples should be mailed with payment directly to the Virginia Tech lab, and results will be issued directly to the sender. Call the Extension office at 434-872-4580 with questions. For additional information on soil testing, check out VCE publication 452-129: Soil Sampling for the Home Garden.
Regardless of your soil‘s condition, adding organic matter to your soil will improve it, and fully-decomposed compost is a great addition. It improves soil structure and water infiltration, while absorbing and holding moisture longer, a real benefit during our hot, dry summers. Compost can be purchased but can also be made at home using yard and organic kitchen wastes. Instructions for home composting can be found in the VCE publication Making Compost from Yard Waste. If you start a compost batch now, it can be ready for planting in 4 to 6 months depending on content and care.
If you have a heavy clay soil in your garden and you aren’t sure how to best manage it, take a look at the Garden Shed article Gardening in Clay. Surprise: the secret is adding decomposed organic matter!
When adding compost to beds, spread a couple of inches on the surface. For new beds to be planted this spring, it can be tilled in. For established beds, we recommend scratching it into the soil surface and letting soil organisms carry it deeper.
Rather than tilling to loosen soil, insert a broadfork or digging fork as deeply into the bed as possible and rock it back and forth to loosen and aerate the soil without destroying the soil structure. Work your way across the beds, advancing several inches with each fork insertion. It is also an effective way to integrate compost below the soil surface without upsetting soil structure.
Weed Management
Best practices for preparing soil for planting now emphasize minimum tilling. Tilling breaks up soil structure and the aeration increases carbon dioxide emissions. Pulverizing soil aggregates leads to increased compaction over the course of the growing season. The biggest issue no-till raises is probably how to manage weeds. Hopefully, most home gardeners are not using glyphosate products to kill garden weeds. Old time mechanical methods of weed hoeing and pulling are great but a lot of work. Organic practices that work are called occultation or solarization. Occultation involves covering beds for 4 weeks or longer with a black tarp, secured around its edges. Occultation denies light, smothering weeds and speeding decomposition of trimmed cover crop remains. Solarization via a clear plastic sheet allows light but gets hotter than occultation which also kills weed roots. Growers report season-long weed-stifling benefits. When the tarp is removed, residue can be left as mulch or composted. The post Black Covers Can Put Weeds to Bed . . . for Good from the Maryland Extension provides occultation explanation and guidance. Solarization guidelines are presented in the article Using the Sun to Kill Weeds and Prepare Garden Plots from the University of Minnesota Extension.
Cover Crop Removal
If you have a cover crop growing, the best time to remove it is after plants flower but before they go to seed. Use a string trimmer to cut it as close to the ground as possible. While residue and plant crowns can be removed and composted, a more common practice, when practical, is to leave the residue on the ground to act as a mulch and organic matter addition. Aerate the soil with a broadfork to reduce compaction and smooth the bed with a rake if needed for seed bed preparation.
It’s Time to Plant
As noted in articles from the last couple of months, the USDA has changed Hardiness Zones boundaries based on climate change-driven warming temperatures. For our local area of Charlottesville and Albemarle County Virginia, our zone changes from 7a to 7b. The net effect is that our average last frost changes from April 15-25th to April 5-15th. This moves suggested early planting times about 10 days earlier in spring (and 10 days later in fall). Virginia’s Home Garden Vegetable Planting Guide from the VA Cooperative Extension hasn’t changed its map yet, but there is a recommended planting/harvesting chart for Hardiness Zone 7b that USDA suggests. The new guidelines make late February to early March the times for outdoor seeding of cool weather vegetables, including beets, carrots, kale, collards, mustard greens, lettuces, peas, radishes, spinach, and turnips. Home-started or purchased transplants that can be planted in the garden this month include broccoli, cabbage, cauliflower, leeks, onion sets, and new asparagus plantings.
Soil temperature is an important factor in successful outdoor seed germination. Soil thermometers are readily available at prices starting at about $15. Consider stem length if you purchase one. For soil, home gardeners only need a short stem; even 4 inches will suffice for seed germination. However, if you get one with a stem of 12 inches or more it can also be useful to monitor compost temperature, where batches are typically 3 or 4 feet deep and the thermometer needs to probe deeply to get a good reading.
Cool weather crops like spinach and lettuce will germinate at temperatures in the 45-50° range, tomatoes need 60-65° soil, and squash and melons need about 70°. A complete guide is available in the Oregon State Extension publication Soil Temperature Conditions for Vegetable Seed Germination.
If you started seeds indoors in February and are moving them to the garden in March, remember to harden them off by putting them outside during the day for progressively longer periods over one to two weeks, once daytime temperatures are above 50°F.
As you move early transplants outside, replace them with warm weather crops that should be transplanted after our last frost. For example, tomato seeds planted indoors in early to mid-March should be ready to transplant outside in about 6 weeks, from mid-April to May 1st. This matches up with our average last frost in Zone 7b of April 5-15. But remember that we had a frost in 2020 on May 9, so pay attention to current weather forecasts and be ready to cover crops overnight if a late frost comes our way.
You can find lots of good advice for seed starting and transplanting in the VCE publication Plant Propagation from Seed and The Garden Shed article How to Start Your Garden Seeds.
Fruit Growing
If you are a fruit grower, fertilize fruit trees 3-4 weeks before active growth begins. Scatter fertilizer evenly under the tree, starting about 2 feet from the trunk and extending just beyond the drip line or end of the furthest branches. A soil test should be performed prior to applying fertilizer. For additional information on fruit trees, visit VCE Publication 426-841, “Tree Fruit in the Home Garden.”
Fruit trees are pruned before growth starts in late winter or early spring to remove dead and diseased branches, remove vertical shoots, open the structure for light penetration, and to shape the tree. Further pruning can be done in summer to “dwarf” a tree, if desirable. Pruning allows the tree to direct nutrients to branches that will bear high quality fruit. The article Pruning Fruit Trees from the University of Nebraska Extension is a helpful resource. For more detail on the effects of pruning try VCE Publication 422-025, “Physiology of Pruning Fruit Trees.”
Bramble fruits such as raspberries and blackberries may be planted in early-to-late March. Plant in moist, well-drained soil containing large amounts of humus or organic matter. For weed control, mulch around newly-planted brambles with an organic mulch. For additional information on how to grow bramble fruit, review VCE Publication “Small Fruit in the Home Garden”.
Now is the time to plant blueberry bushes. Different varieties of blueberries have different requirements for “chilling hours” — i.e., the number of days with temperatures between 35° and 45°F. They also require very acidic soil for best growth. It makes sense to make careful choices when acquiring plants. The Garden Shed article Blueberry Cultivation in the Home Garden explains further.
If you have established blueberry plantings, the publication Pruning Blueberries from the Maryland Extension offers excellent pruning advice with illustrations.
I hope this information provides guidance and motivation to help you get things going. It’s great to be out in the garden again. I hope to see you again next month at The Garden Shed.
Resources:
Featured Photo: Backyard garden in March. Photo: R Morini
“Virginia’s Home Garden Vegetable Planting Guide and Recommended Planting Dates,” Va. Coop. Ext. Publication 426-331, http://pubs.ext.vt.edu/426/426-331/426-331.html
“Tree Fruit in the Home Garden,” VA Coop. Ext, Publication 426-841, https://www.pubs.ext.vt.edu/content/dam/pubs_ext_vt_edu/426/426-841/426-841_pdf.pdf
“Soil Temperature for Vegetable Seed Germination,” Oregon State Extension, Soil Temperature Conditions for Vegetable Seed Germination | OSU Extension Service (oregonstate.edu)
