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The Sciences

Want to Start a Vegetable Garden? Here’s How, According to Science

You don’t need a proven green thumb to give it a shot. Expert horticulturalists share their top tips for planting sprouts at home.

By Leslie NemoMay 29, 2020 9:30 PM
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(Credit: ABO PHOTOGRAPHY/Shutterstock)

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With many of us stuck at home, it’s easy to feel the pull from your yard or apartment balcony. Maybe the produce aisle has been out of tomatoes one time too many. Maybe it’s pure boredom. But the fact is: People are gardening — and many for the first time.

Growing vegetable gardens takes a lot of work, but don’t put too much pressure on yourself for making mistakes, or having a rough time getting started. Barb Neal, a horticulturalist at the Cornell Cooperative Extension in New York, says even she and her partner, who is also a horticulturalist, don’t always manage perfect garden protocol. They didn’t get around to cleaning up their home garden and pulling weeds before the first snowfall last year, for example. “And, boy, did we pay for it,” she says, with lots of weeding and fertilizer additions this spring.

Even the pros make mistakes sometimes. “We know what we’re supposed to do,” Neal says, “and then sometimes we don’t do it.” So if you don’t have a tried-and-true green thumb, that shouldn't stop you from giving home gardening a shot. Here are some steps you can take to make it a success — and the science explaining how it all works.

Get Your Soil in Good Shape

Healthy soil is teeming with microorganisms, filtering water and exchanging particles with the air above it, Neal says. It’s a thriving little community, and taking care that it is fit to grow your produce will reward you in the long run.

The soil just outside your home might be healthy enough to host your garden, particularly if you live in rural or less densely populated areas. In urban settings, conditions could look different, says Sam Wortman, a horticulturalist at the University of Nebraska-Lincoln. Construction and foot traffic compact soil, and if it’s too dense, roots struggle to spread and water doesn’t filter properly. Urban soil can also host higher levels of contaminants, like lead. The element naturally occurs in the ground, but city soil has a history of more exposure to leaded gasoline and house paint, and tends to hold more of the material.

If this is a concern, it’s worth trying raised beds — essentially, wooden boxes that sit aboveground, filled with healthy soil and compost. These setups let gardeners bypass any soil issues they have in their yard and put together the ideal growing scenario. In some of Wortman’s research, he and his team found that raised beds in urban areas grew at least twice as many veggies, like cilantro and kale, than traditional in-the-ground planting.

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Raised garden beds can be a good alternative to in-ground planting in settings where naturally occurring soil is unavailable or devoid of nutrients. (Credit: Alison Hancock/Shutterstock)

Once you’re confident the soil is healthy, it’s important to make sure all the essential nutrients a plant might need are actually accessible to the growing roots and shoots. Depending on the soil’s pH levels, or how acidic or basic it is, some nutrients may be bound to other molecules in the ground, and therefore not available for your plants, Neal says. Acidic soil holds onto macronutrients like nitrogen and calcium very tightly, and basic soil monopolizes micronutrients like copper and zinc. 

Vegetables like a mix of both macro and micronutrients. The best compromise between the availability of the two sits at a soil pH of about 6 to 7, Neal says. To figure out your soil pH, try a do-it-yourself pH test kit or see if the agriculture extension office in your state has a mail-in soil testing option. The results might tell you to make your soil more acidic by adding sulfur, or more basic by adding pulverized limestone, for example.

Don’t Go Crazy With The Seeds

As tempting as it is to pack your plot with all the peppers, tomatoes and zucchini you can, Neal says to follow the directions on your seed packet to determine how far apart to plant each seed. If the soil is too crowded, foliage from leafy plants will merge as the sprouts grow, creating a canopy that cuts off airflow among the plants. This can lead to humidity buildup, and humidity welcomes mold and fungus. 

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Be sure to spread seeds out when planting so the soil doesn’t get too crowded. (Credit: lovelyday12/Shutterstock)

To counteract humidity, you can pluck some of the lower-sprouting leaves on your plants. This helps with veggie growth, too. Tomatoes, for example, sprout tiny leaves called suckers that sit at the junction between the plant stem and branch. The plant invests resources in growing suckers because that’s part of its natural life cycle, but the leaves aren’t crucial to the plant’s survival. Pulling some leaves off directs the plant to funnel more of its nutrients into the big red fruit you’d like to harvest for yourself. 

When Watering, Be Precise

The mold and fungus that can grow from crowded leaves might get worse when you water the greenery, too. Try to aim the water so that it goes right to the base of the plant. This technique has the added bonus of keeping as much water away from weeds as possible. Even if the top of your soil looks a little dry, that’s OK, Neal says.If you stick your finger in, you’ll feel that it’s moist where the roots are. That’s kind of an ideal situation.”

If you’ve opted for the wooden box approach, large proportions of compost can make the soil porous and unable to hold onto water for longer periods of time. Veggies in these conditions might need watering more frequently. Wortman recommends setting up timed irrigators that drip water in the right spots on a regular basis to make sure these handcrafted soil mixes are moist enough.

Tackle Weeds Early

In most cases, weeds are somewhat inevitable. Their seeds live in all kinds of soil, and are so perpetually present that horticulturalists refer to this seemingly endless source of annoyance as the “weed seed bank.” With the right conditions, the seeds will sprout along with your vegetable plants.

One way to counteract weed growth is to starve them of the resources they need. Neal’s watering recommendations are one way to keep them from getting hydrated — Wortman adds that wood chips, plastic barriers, straw, cardboard or other kinds of mulch also keep weeds from growing. These materials, dispersed on the soil in between plants, cool the soil and block out light.

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Tackle weeds early to avoid unwanted growth and competition for resources in your garden. (Credit: David Prahl/Shutterstock)

Research shows that when using organic materials, and not plastic sheeting, for this task, the layer needs to be about 3 inches deep to have these effects, Wortman says. If you opt for wood chips or straw, note that they can suck up nitrogen and keep it from your vegetables. You can counteract that deprivation by applying fertilizer directly to your seedlings so the only plants thirsting for nitrogen are weeds.

You can also try to start your planting with as few weed seeds in the soil as possible. Remember how the wooden box plots, filled with your own soil and compost, are handy for dodging any nutrient problems in your own backyard? Well, that logic applies to avoiding weed seeds, too, especially if you buy certified compost. 

As plants and manure degrade into compost, the bacteria responsible for the transformation produce a lot of heat, Wortman says — so much heat that the internal temperature of the compost kills seeds. Professional composting services churn the material so that every bit of the former food scraps and plant parts reaches that temperature. Technically, at-home composters could do this too, but those piles typically aren’t managed as well as or as intensively as those by professional services, and might not generate enough heat. Wortman recommends buying compost if your goal is to avoid weed seeds.

Ask For Help

There are all kinds of online resources from departments like Neal’s. But if you want to talk to someone directly, reach out to an agriculture extension office, she says. They are all over the country, and full of experts who know how to help plants grow in your region.

And if you’re lucky enough to live next to someone like Neal or Wortman, maybe you can ask them for advice, too. When neighbors come to Wortman for advice, “most of the questions people have are ‘what plant is this?’” he says. “I don’t do much of that — I work more with crops, and it’s not hard to memorize all the crops I grow.”

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