Growing Onions in South Texas

Growing Onions in South Texas

Onions are a very low maintenance crop for your garden. I usually plant mine in an out-of the-way spot for two reasons: It is a long-season crop, and it is almost a set-and-forget type of crop. However, there are some things  you need to be aware of when growing onions in order to get the best crop.

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Types of Onions

There are several onion varieties for Zone 9. The main criteria for onions in this climate is that they be a ‘short day’ variety. Paradoxically, this means they get 10-12 hours of sun per day, which to me is a pretty long day. When the day hits this number of sunlight hours per day, the onion will start to form a bulb.

A ‘long-day’ onion gets 12-14 hours of sun a day before they begin bulbing. These onion varieties are best suited for northern climates. So, the difference between short and long day varieties is a matter of relative percent of sunlight. You need a lot of time for the onion plant to put out leaves before it hits the sunlight threshold and begins to form a bulb. The more leaves, the bigger the onion.

So, Zone 9 varieties are:

  • 1015Y Texas Super Sweet–a yellow, sweet, open pollinated onion, that takes 105-110 days to mature and keeps 2-3 months. You can get this variety in the grocery store.
  • Red Creole–a dark red onion that takes 100-110 days to mature, and keeps 6-7 months.
  • Southern Belle Red–a red, sweet onion, that takes 105-110 days to mature and keeps 2-4 months.
  • Texas Early White–a white onion, with 110 days to mature and keeps 2-3 months.
  • Texas Legend–a yellow, sweet, open pollinated onion variety, 100-105 days to mature that keeps 3-4 months.
  • White Bermuda–a white onion that takes 85-95 days to mature and keeps 2 months.
  • Yellow Granex, AKA Vidalia–the yellow onion you often see in the grocery stores. It takes 100 days to mature, and keeps 1-2 months.

You can see that the type of onion you grow depends on what you are going to do with it, or how long you expect to store it.


Onions require full sun, good drainage and loose soil. The looseness of the soil determines how big your onions will get. Hard, clay soils will yield small onions.

You can plant onion seeds or bulbs. Plant them 4-6 weeks before last spring freeze date.

At planting, fertilize with a high Phosphorous fertilizer. On your fertilizer label, phosphorus is the middle number, for example, 5-10-5). Put the fertilizer in a 4″ deep trench. Cover it with 2″ of soil. Then, plant your onions on either side of the trench, 6″ away, not on top of the fertilizer. Put bulbs 1″ deep. If you want mature onions, plant them 4″ apart; if you want immature onions, plant them 2″ apart, then pull the immature ones to let the others grow to maturity.

Growing Onions

Water your growing onions regularly. Onions have shallow root systems that can easily dry out. Fertilize every two to three weeks after planting with a high nitrogen fertilizer (the first number on the label, for example 10-10-10) in the center trench. Weed to prevent competition for nutrients. Mulch after the onions begin growing to assist in suppressing the weeds.

When the ground begins to crack around the onion, bulbing has begun. Stop fertilizing at this point.

Onion leaves predict the size of the bulb
Onion leaves predict the size of the bulb

Onion sizes are determined by how many leaves the plant has. Each leaf equals an onion ring. Larger onions below ground have more leaves above ground.


The onions are ready for harvest when the tops begin to turn brown and fall over. At this stage, the onion leaves have stopped growing, and the onion is ready for storage. Dig the onions in the early morning, and lay them on the ground, or in a dry protected spot, to dry for two days. Then cure for an additional 10-14 days in a warm and dry spot; if it is going to rain, dry them indoors. Keep the tops and roots on the onions until they are dry to prevent rot. Also shade or cover the drying onions to prevent sun scalding.

Saving Seeds

Flowering onion plant
Flowering onion plant

Onion plants have seeds in the second year of growth. Most garden supply stores will sell either bulbs or seeds, and most gardeners buy the bulbs. If you want to save onion seeds, leave a onion plant to grow into the second year. It will produce flowers and seeds in the late summer of the second season. When the flowers dry, and the seeds begin to fall, cut the flower heads, let them dry, and gather up the black seeds. Store the seeds in a cool dark place, and use them the next growing season.


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Comment below to share your experiences with growing onions!

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