When it comes to growing healthy, tasty tomatoes and other summer vegetables, success begins with the fundamentals.

“Basically, all plants need the same kinds of nutrients, although the proportions may vary some,” said Pat Patterson, an Oregon State University Master Gardener volunteer for more than 40 years. “There is the NPK—nitrogen, phosphorus and potassium—and then there are calcium, magnesium and sulfur, and the 16 other micro elements.”

This may seem like a lot to rustle up for your vegetables. “Not really,” said Pat, who teaches OSU extension service classes in soils and vegetables. “Ninety-five percent of what plants need is nothing that you can buy in a bag,” she said. And that 95 percent? “Carbon dioxide and water,” she explained. That, along with sunlight, is what plants require for photosynthesis, which is how plants make their own food from soil elements.

But how do you know if you’ve got enough of the other five percent to grow healthy vegetables?

Feeding Your Soil

“You really need to have the soil tested by a soil testing laboratory. Those little test kits that you can get are worthless,” she said. “Frequently, your local extension office can do it, or, there are some very good labs out there.”

Basic soil tests cost around $20 but you’ll get more than just a bunch of numbers. “They’ll give you the test results and then interpret them for you,” she said. And if you want to get gardening without waiting for the results, take a good look at your garden spot. “If it’s growing a good crop of weeds, the soil is probably pretty good.”

Still, your soil test may show some deficiencies that you can correct. But, just throwing a handful of fertilizer into the dirt won’t necessarily produce fabulous plants.

“Quick-release fertilizer feeds the plant and then it’s gone,” she said. “You need to keep nutrients in the soil available to the plant. You’re feeding the soil, not the plants.”

Soil temperature and a balance of nutrients are critical for allowing the plants to take up the nutrients. The reason: “Plants aren’t able to take up nutrients if the soil is too cold. They don’t do much below 50 degrees F.”

Avoid Rookie Errors

“If people are beginning organic gardeners, they tend to under-fertilize and if they’re not organic gardeners, they often over-fertilize,” she said. Or, she added, some gardeners believe that they merely need to add compost to the garden, “and then wait to see what happens.”

Compost, which becomes humus when soil micro-organisms break down plant material, is a great addition to soil but it takes time to establish an optimum ecosystem.

“If you use compost year after year, you build up a reservoir of nutrients and life in the soil,” Pat said. “It’s the process of creating a new soil. You can’t change the soil texture, but you can change the soil structure.” She explained why the right soil structure is absolutely necessary for healthy plants. “If you have heavy, clay soil, the roots have to fight to get the nutrients off the clay. If you have really clayey soil, I’d recommend building a nice raised bed.”

Some clay in soil is good as it helps hold nutrients, while a completely sandy soil holds few nutrients. The best soil is a sandy loam with between 10 and 30 percent clay. “What we do is add organic materials, which hold even more nutrients. You’re looking for soil with good nutrient-holding capacity. The key is the soil life and the organic matter,” she emphasized.

Sustainable Fixes

It’s not an absolute necessity to add animal manures to boost soil nutrition and some gardeners opt to purchase products to make up for any deficits. Pat is skeptical of this quick fix. “I feel that if people are buying things that came from, say China, when we have the materials here, then that’s not terribly sustainable. Or if we’re robbing bat caves for the guano, that’s not sustainable either. Everything has its ripple effect.”

However, she added, “there may be times when you need a liquid form of fertilizer to get things going. I’m fond of liquid fish emulsion and kelp.”

Also, gardeners should rotate the type of fertilizers they use. “You don’t want to use the same fertilizer for years and years. You may have something missing in the nutrition that plays out slowly over the years.” Which means that over time, your garden grows less productive.

Watering & Fertilizing

Newly-emerged vegetable seedlings’ first fertilizer should be applied as an easy-to-absorb liquid type when it forms its first true leaves, Pat recommends. That’s because seedlings don’t have a mature enough root system to readily absorb other fertilizers.

When transplanting a young plant to the garden, you can add fertilizer around the root zone of the plant. That’s probably going to be enough for the season.

Too much fertilizer is not a good thing because it “can burn the roots,” she explained. “And if the fertilizer proportion is out of balance, it may leach out readily and can mess up the availability of other nutrients such as calcium.” For tomatoes, in particular, that means the plant won’t have enough structural integrity as it grows.

Summer vegetables can be thirsty, especially when temperatures are at their peak. “If you don’t use enough water, there will be a lack of sugars and they will be dry,” she said. “Tomatoes need to have water right up to when they actually begin to ripen fruit. As they get a bigger root system, they can go longer between waterings but if they get shorted with water, it could kick off blossom end rot.” That’s because the plant will rob moisture from its fruit to sustain itself.

Other vegetables, such as corn, are especially thirsty. “You have to water corn and leafy greens like mad. I think it is hard to overwater them. They also take a lot of nitrogen.”

Cantaloupes, on the other hand, produce watery fruit if irrigated too frequently. For vegetables such as onion and garlic, you need to stop watering once they are mature to prepare them for harvest.

In water-scarce areas, wise gardeners have learned that building up a soil’s water holding capacity to 10 to 15 percent, then mulching heavily, will allow them to seriously cut the amount of additional water their plants will require, she added.

Harvest Your Vegetables

Summer vegetables are annuals and while you can’t really speed up the harvest, you can extend it. “With annuals, the whole business is to make fruit and seeds,” said Pat. By keeping the veggies picked as they’re ready to harvest, the plants will keep flowering and fruiting, giving you more produce to eat fresh and put by.

This article is from a previous issue of The New Pioneer. Grab your copy at

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