Will Yellow Sorrel Kill The Other Plants In My Garden?

Yellow wood sorrel is easy to confuse with clover because of the shape of the leaves. [UF/IFAS]

Oxalis, the kind with the tiny yellow flowers, is taking over my beds, borders and yard. I'm ready to take drastic measures to get rid of it, at least in my borders. Can I use RoundUp on it in the winter?

Of the over 800 different species of oxalis, the plant you describe is sometimes called Yellow wood sorrel (Oxalis stricta) and is the bane of many gardeners' best efforts. Year after year this perennial terror returns, always seeming worse than it was before you spent hours hand-pulling.

Yellow wood sorrel is often confused with clover because of the similar leaf structure. The wood sorrel has a three-petal leaf with heart-shaped lobes. They grow year-round in north Florida, in full sun to part shade; in moist soil or dry. A single plant producing as many as 5,000 seeds. Hand pulling is often ineffective because if any of the plant's complex bulbous rhizomes is left behind in the soil, a new plant will develop.

Both pre- and postemergence herbicides are available to control yellow wood sorrel. The effective herbicides are listed in the UF publication, "Yellow Woodsorrel (Oxalis) Biology and Management in Turf," found at https://edis.ifas.ufl.edu/ep385.

Though glyphosate, the active ingredient in RoundUp and many other contact herbicides, is not listed as a recommended product for oxalis control, oxalis is nonetheless listed on the RoundUp label as a weed for which the product is effective. One concern about glyphosate is it is a non-selective herbicide that will damage or kill other plants or grasses with which it comes in contact. Therefore, avoid using it on windy days. And always read label instructions carefully and use these chemicals as directed.

According to the manufacturer of RoundUp, the ideal temperature for applying this particular product is between 53 and 77 degrees Fahrenheit, making this a good time for its use. Postemergence herbicides are most effective when the weeds are actively growing.

Many gardeners are looking for organic or homemade preparations as alternatives to commercially produced herbicides. There are several ways in which these alternatives differ from products from the nursery center.

• These herbicides act by burning back the tops of perennial weeds, but perennial weeds will recover quickly and require reapplication.

• The quality and strength of the homemade products will differ from batch to batch.

• Just as manufactured chemicals can be harmful to people and pets, chemicals from the pantry can also cause injury. Plus there is no label to help you make decisions regarding safe applications.

For those gardeners looking to fight their weeds with vinegar, the University of Maryland Extension's publication "Vinegar: An Alternative to Glyphosate" (https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/Vinegar-AnAlternativeToGlyphosate-UMD-Smith-Fiola-and-Gill.pdf) includes an extensive list of pros and cons so you can make informed decisions for your garden.

Mention of a commercial or herbicide brand name or chemical does not constitute a recommendation or warranty of the product by the authors or the University of Florida, Institute of Food and Agricultural Sciences, nor does it imply its approval to the exclusion of other products that may also be suitable.

My grocery store orchid has lost its blooms and is sitting idle on the kitchen window sill. Because I've never been able to urge these orchids to rebloom, and I've been told that plants need sun to flower, I thought I'd put it in a sunnier location. Now the silly thing is growing purple leaves! This can't be normal. What's causing this?

Those "grocery store" orchids are usually Phalaenopsis, also called the moth orchid. That's a good guess because this species makes up over 75 percent of all orchids sold. They are very adaptable to the typical home environment and their long arching sprays of colorful flowers remain fresh for several months, from winter or early spring.

To the question of reblooming, the amount of light the plant receives is probably the key factor to getting the plant to re-flower. If the light level is too low, the plant may remain healthy but not produce blooms.

But how to know what light level is right? The plant's leaves will tell you.

A healthy Phal in proper light has large leathery light-medium green leaves.

Too little light produces leaves that are dull, dark emerald green, and very stiff. In that case, find a bright window that provides diffused light, like the environment this epiphyte would receive in its native Southeast Asia environment.

If the leaves are turning red or purple along the edges (a.k.a, the margins) the plant is getting more light than it wants.

If the upper leaves are pale or yellowish but still plump and firm, the plant is most likely receiving too much light. Phalaenopsis leaves will burn if exposed to direct light.

It can be a bit of a trial and error to find exactly the right spot, but your plant will reward you for it.

Along with finding the right light, most orchids, including the Phalaenopsis, need a significant temperature difference between day and night to set buds. In the fall, let your plant spend the evenings in an area 15-20 degrees lower than the daytime temperatures. Bring them indoors when the evenings dip into the 50s.

One of the biggest challenges to raising healthy Phalaenopsis orchids is proper watering. Most authorities on orchid growing, including the University of Florida, will instruct you to thoroughly drench the plant no more than once a week, allow it the completely drain and to become partially dry between watering.

However, many home growers and some commercial ones are advocates of using ice cubes on a weekly basis to irrigate plants. The practice is so popular that The Ohio State University conducted a series of experiments this past summer that measured the efficacy of this method. Their conclusion? "Yes!... ice cubes are a practical way to water Phalaenopsis orchids grown in bark media." To read the details of their study and findings, go to http://u.osu.edu/greenhouse/2018/07/12/watering-phalaenopsis-orchids-with-ice-cubes/.

As always, you can find more information on growing orchids at the University of Florida/IFAS site. Start with "Orchids" at http://gardeningsolutions.ifas.ufl.edu/plants/ornamentals/orchids.html, and follow the links to specific topics and articles.

Paula Weatherby is a Master Gardener with the Duval County Extension Service and the University of Florida/IFAS. For gardening questions, call the Duval County Extension Office at (904) 255-7450 from 9 a.m. to noon and 12:30 to 3:30 p.m. and ask for a Master Gardener.