Keep it Green, by Michael Womack
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Saturday, October 13, 2001

Repot plants to allow new root growth

Before you take in your potted plants for cold weather, consider repotting your tropical plants. A bigger container will give your favorite tropicals a chance to expand their root system during the winter months. It also will help you to monitor their moisture level better.
   If a plant is rootbound, it will often dry out faster than plants with plenty of room in the pot for root expansion. Since the pot is full of roots, there is little soil material left in the pot to hold water and nutrients until the plant needs them.
   Room to grow
   If the roots are circling inside the pot when you remove it, you need to score the roots. Cut the root ball about 1 to 2 inches deep in three or four places from the top to the bottom. This encourages new roots to grow normally. If you don't break the circular root growing pattern, the roots will continue to grow in a combined circle.
   When choosing a bigger pot, give small plants about one inch of extra pot space in all directions. For example, repot from a 4-inch container to a 6-inch one. A 10-inch potted plant will typically be replanted in a 14-inch pot.
   Whether you select a plastic, fiberglass or clay pot is a matter of preference and style. Clay pots allow more "breathability" but may become too heavy as pot sizes increase. That added weight may be advantageous to plants that stay in windy patio situations most of the year. Plastic, fiberglass and foam pots provide attractive, lightweight alternatives. The trick is to weigh the advantages and disadvantages of each type according to your needs.
   Whatever you select, the pot should have a hole in the bottom for drainage. A plant without a drainage hole will usually develop root rot. To prevent soil from washing out the drainage hole, place a broken piece of clay pot over the hole.
   Make sure you use a good, well-drained potting mix. Purchase potting mix and not potting soil. A potting mix contains organic matter such as peat or finely composted bark mulch along with perlite and/or vermiculite for drainage. Potting soil will usually contain a heavy clay soil or some sand. If you are unsure of the contents of a soil mix, read the bag.
   And spend a little extra. If you buy a 40 quart bag for 99 cents, chances are you are getting a large amount of clay and other cheap soil in the bag. The bag will typically be very heavy even when dry because clay doesn't have very large air spaces. Organic matter that typically has good aeration or air spaces between soil particles will be considerably lighter than clay when dry. That allows more air and good drainage, two keys to strong root growth.
   Let them breathe
   Plant roots must have good aeration to thrive. Research has shown that roots that remain underwater will begin dying in as little as 24 hours. Don't allow plants to stand in water for periods longer than 30 minutes. More plants die when gardeners stand them in a saucer of water with the good intention that the plant will absorb it later in the week.
   Peat is the best organic material in potting mixes and is also the most expensive. It effectively holds water and nutrients for plant growth. Some manufacturers also use composted pine bark, kanaff and even rice hulls to make an inexpensive, but light, potting mix.
   If peat dries out, it must be watered at least two to three times within a few hours. Once water starts to penetrate the peat, the potting mix holds more water with each subsequent watering. You can also leave the plant in a saucer of water for about 30 to 45 minutes to allow more water to be absorbed; however, extended periods of standing water will again reduce aeration and promote root rot.
   Take time to evaluate your plant needs this fall, and repot those rootbound plants. It will make your wintertime care easier and will result in fuller, healthier plants next spring.
  
  

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Michael Womack is a horticulturist with the Texas Agricultural Extension Service. Got a question? Michael Womack will answer landscape and gardening questions. Call 886-4648, category 3025 to record your question. Write Keep It Green, Corpus Christi Caller-Times, P.O. Box 9136, Corpus Christi, TX 78469 or email wm-womack@tamu.edu

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