Green Thumb – Ask a Master Gardener about Vegetables

Posted: June 18, 2020

“Life expectancy would grow by leaps and bounds if green
vegetables smelled as good as bacon.”
  Doug Larson

This year, many people are showing an interest in growing their own vegetables. For some, there is comfort in having some control over their food source. For others it has been a search for something to do while forced to stay at home.

In this time of social distancing the DeKalb County Master Gardener Horticulture Help Desk is not open for questions by phone. However, you can send us an email at When leaving your question, be sure to give detailed information about what you are looking for. Feel free to include pictures and anything else that might help with research. Include your phone number and mailing address.

Here are some questions about vegetable gardening you might have been wondering about.

Q:  Can I use left over seeds?

A: Seeds last longer when stored in a cool, dry place. Some seeds like cabbage last four years or more, while parsley last a year or two. You can test the viability of your old seed by placing 10 seeds on a slightly damp paper towel. Roll or fold it up, place it in a closed plastic bag and place it in a warm place (above 70 degrees).  Seed packets list the average germination time, but if you don’t know, check them in 7-10 days.  If the germination rate is less than 70%, it’s better to buy new seeds. Between 70-90%, just sow them thicker than normal.

Q:  What vegetables can I grow in the shade?

A: Most vegetables need at least six hours of sunlight per day and won’t grow well in complete shade. Leafy vegetables such as lettuce, spinach and parsley tolerate more shade compared to the root vegetables. Most herbs perform well in partial shade or full sun.

Q:  What can I plant after the leaf lettuce has been picked?

A: Succession planting can make good use of your garden space. After lettuce and spinach, plant warm weather crops like beans, if in full sun. Then in late summer replace the beans with radishes, lettuce, spinach, beets and turnips. These vegetables will mature in the cooler fall weather.

Q:  How can there be so many blossoms on pumpkin plants but few or no fruit developing at the onset of flowering?

A: In cucurbits (pumpkins, squash, zucchini and cucumbers) the male flowers start to open first and start attracting bees. Then, when female flowers appear, good pollination is ready to take place. Female flowers have a bulge in the stem just under the flower. 

Q: What causes bitterness in homegrown cucumbers?

A: Cucumbers naturally produce a bitter tasting chemical called cucurbitacin. If a plant is under stress from lack of water, extreme heat, or especially cold, the cucurbitacin can spread from the roots, stems, and leaves into the fruit. It’s more concentrated in the stem-end and the peel. Less is found in the interior of the fruit.

Q:  Can I spray a broadleaf herbicide on my asparagus
to get rid of weeds?

A: No. It can injure asparagus. Only spray before asparagus spears emerge in the early spring. When you cut back the dead asparagus foliage in late fall, pull any visible weeds so they don’t overwinter. A mulch will block weed growth and protect the asparagus through the winter.

Q:  What does a Tomato Hornworm turn into?

A: The size of the mature caterpillar can strike fear and loathing, especially if you find your first one by touch. They are harmless to humans, but should be removed or they will devour a plant in record time. It is the larva of the Five-Spotted Hawk Moth. They have a stout body and a wingspan up to five inches. They fly around at night depositing their eggs. This should give you pause if you ever think about tinting your hair tomato-leaf green.

Janice M. Weber – University of Illinois Extension, DeKalb County Master Gardener