Sunlight: The Key to Great Vegetables

By Steve Reiners, Professor and Chair, Horticulture Section, Cornell University, Cornell AgriTech. This is part of a series of columns that he wrote about vegetable gardening during the pandemic that ran Spring-Summer 2020. Read more articles from 2020Read later articles in this series.

April 3, 2020

As in real estate, the three most important factors to success in vegetable gardening are location, location, and location. You want a location with abundant sunshine, good drainage, away from shrubs and trees and their competing roots, and close to an irrigation source. The most important factor is the amount of sun. No vegetables will grow in a shady spot. Without enough sun you’re guaranteed to be disappointed, with tomato plants eight feet high with only a few small tomatoes.

3 - 4 hours of sun

  • This is the minimum! If that’s all you get you will only be growing leafy crops like lettuce, spinach, Swiss chard, collards, and endive.

5 - 6 hours of sun

  • Think about root crops like carrots, radishes, beets, onions and potatoes, in addition to the leafy crops. 

7 - 8 hours of sun

  • You can grow  fruiting crops like tomatoes, peppers, squash, cucumbers, and beans. 

If your yard does not have any direct sun, you cannot grow vegetables, no matter how rich and healthy your soil is. But unlike a lack of light, there are things you can do to improve a poor soil.  No vegetables grow well with wet feet.  If the only sunny spot in your yard has standing water, you’ll need to take steps to improve it.  If the drainage problem is due to high clay in your soil, working in sand and bulky organic matter like compost will help.  Or you can create raised beds 4 to 6 inches high.  Frame the beds with lumber and fill with topsoil or compost.  Make the beds no more than 3 feet wide so you can reach them from both sides without having to step on them.

Trees and shrubs can have surprisingly long roots that can easily find their way to the garden.  And who can blame them as their roots are searching for a source of nutrients and water and what better place to go than a well-maintained garden.  Try to locate the garden away from competitive roots.  Also, one word of caution when it comes to roots.  The roots of black walnut trees release a toxic compound that can kill some plants.  Tomatoes, along with peppers, eggplant and potatoes are very susceptible to this compound and plants will wilt and die in the presence of black walnut roots.

Finally, at some point in the summer, your vegetable garden is going to need water.  Tomatoes grown in dry soil are guaranteed to come down with blossom-end rot, and drought stress will result in a  decline in yield and plant health for any crop.  That’s why it is so important to be near a water source.  You’ll be much more likely to water the garden if it’s easy to do.  Later this year, we’ll talk about easy ways to irrigate but for right now, plan so irrigation is easy.

In the garden this week

Spring officially began two weeks ago, but soils are still pretty wet and cold.  Still, it is not too early to make your first planting if you have a patch of ground that is not too wet and can be lightly worked.  Spinach and peas can be planted the last week of March here in upstate New York.  Unlike most seeds that rot in a cool, wet soil, these crops will germinate and thrive even when the soils are still cool.  You can speed germination by placing a  sheet of clear plastic on the soil over the row.  Put some rocks or dirt on the plastic to keep it from blowing away.  When you see the first seedlings poke through the ground, remove the plastic.

Next week we’ll talk about developing a garden plan that allows you to maximize even a limited garden space.

Eating lots of fruits and vegetables is important to keep our immune systems strong. There is a lot of bad if not dangerous info out there about washing fresh produce to avoid COVID-19.  Rather than believe your friend’s cousin’s Facebook page, I went to an expert, my colleague at Cornell, Dr. Betsy Bihn, Director of the Produce Safety Alliance.  Here’s what she recommends. “The best thing to do with produce before eating it is to run it under cool running water to remove any residual soil or dirt. If it has a tough skin, you can use a clean vegetable brush to gently scrub the surface.  Some people worry they need to do more due to COVID-19 concerns, but they do not.  There is currently no evidence that that the coronavirus that causes COVID-19 is foodborne. Washing produce with soap or dilute bleach can be dangerous and lead to other health issues, so please do not do that.”