Even the Dusty Miller is purple!
Thanks~
Sandy
What's causing the purple foilage in my container plants?
Could be downy mildew. Do you have pictures? Downy is tough stuff, much harder to get rid of than the powdery kind.
Good bet it was a Phosphorous (P) deficiency brought on by cool soil temps (this can occur even when normally sufficient P is present in soils). A common symptom of P deficiency is an accumulation of anthocyanins - purple leaves. This happens because P is required to make a compound that is needed to convert sugars to starch or to load sugar into phloem for transport to other plant parts. Low soil temperature reduces root growth, roots absorb less P, free sugars accumulate, and leaves turn purple. As soon as soil temperature warms enough to stimulate root growth, free sugar concentration will usually drop, anthocyanins are broken down and leaves return to a normal color, unless soil truly is deficient in P.
However, P deficiency is not the only cause of purple leaves. Nearly any cultural condition that limits growth (the use of photosynthate - sugars), but does not limit photosynthesis (sugar production) can cause anthocyanin build up. Purple leaves will most often occur with periods of cool, but sunny days.
Al
Hi Al...thanks for your wisdom! I don't know if its the soil temps...we've had above normal temps (90's) for several days, lots of sunshine, but probably less than two inches of rain since April. I have fertilized with Miracle Gro, Fish Emuslsion and watered daily when needed....
For an example (believe it or not!) the Thunbergia vine started from seed in March is flowering, but still only two to three inches tall. In addition to the foilage discoloration, many of the plants are not growing. I purchased and planted Blue Salvia (annual) from a greenhouse in May. It is still three inches tall. The plants that should be vining just aren't.
Could it be something in the growing medium I purchased from Big Lots? I am just getting SO frustrated since these containers (19 of them) are for my employers property and I wanted them to look good. I can't explain how poor some of them look....
Thanks for your help~
Sandy
Absolutely - soil can cause purple tinting on leaves. Note above: "Nearly any cultural condition that limits growth (the use of photosynthate - sugars), but does not limit photosynthesis (sugar production) can cause anthocyanin build up."
I bet your soil is poorly drained & remains wet for extended periods? This affects root function, which effects plant development. Since photosynthesis continues, but translocation of photosynthate lags because of poor root function, anthocyanin builds up & leaves turn purple.
Soils are the foundation on which all good container plantings are built. Drainage is the bottom and most important block in the foundation. Protect drainage & aeration at all costs & the rest is easy.
Though you can't improve aeration (practically speaking) once a soil is built, you may be able to improve drainage in soil that remains wet too long. Insert a length of absorbent material into the drain hole to act as a wick. The wick can rest on soil that will allow water to soak in, or on a deck or railing where water will flow away from the container. The key is not to allow the wick to sit in a puddle of water or its effectiveness is greatly diminished.
I will offer a post on container soils & drainage issues when next I have time to put it together. You may find it of some interest.
I wish you well.
Al
Excellent post, Al. Very interesting. My understanding of what goes on in plants is enhanced greatly. I will look forward to your future post on container soils.
Thanks again Al...you are SO informative! Still, I don't believe the drainage is an issue. The pots drain freely....if I water in the morning I sometimes have to water again later in the day because they dry out so quickly. The growing medium tends to pull away from the sides of the containers when it gets too dry, so I do aerate the soil while I'm watering as to prevent the water from running totally down the inside walls of the pots.
Thanks!
Sandy
Perhaps it is simply a bonafied P deficiency then - same symptoms - different cause. Thank you for the kind words.
Al