My husband bought a huge bag 40 lbs. of gypsum (calcium sulfate) for $6.99 at the feed store. The ingredients are: 21% calcium and 16% sulfur. My alkaline clay is tested deficient in sulfur, and barely adequate in calcium: my roses have yellowish young leaves and stunt growth.

Sulfur deficiency results from either too alkaline, or too acidic soil. It's often leached out of heavy-rain soil. The largest international nursery BALL that sells annual plants/flowers put gypsum in their potting soil. BALL potting soil is highest-rated in the Container-Forum.

My neighbor works for Ball, and bought for me their potting soil. The ingredients are: composted pine fines, peat moss, vermiculite, perlite, lime and gypsum. It's far superior to MiracleGro potting soils (don't have gypsum). Gypsum is added to potting to maximize water and nutrient-uptakes, and to de-salt the salt used in chemical-fertilizers.

See link below on sulfur deficiency (gypsum is 21% calcium, and 16% sulfur). Below is Paul Neyron rose (notorious for fungal diseases). It's very healthy in Ball potting soil with gypsum:

Here is a link that might be useful: Sulfur Deficiency and North Carolina State University

This post was edited by Strawberryhill on Mon, Aug 26, 13 at 9:18

To play the devil's advocate, would the sulfur lower the ph such that you might run into problems from a lowered ph ? Or, is the application rate to small to impact your ph ? Would you happen to know the ph of the soil for Paul Neyron before and after the use of gypsum ? I enjoy your posts, you look at plant nutrition and health in more diverse ways than what I am used to.
Don

Hi Don: I love your thoughtful questions, much appreciated. Months ago I asked the same questions, and spent hours researching on that. My B.S. is in Computer Science, minor in Chemistry, so I always double-check on accuracy.

My tap water pH is 8, so it counteract the sulfur part of the gypsum. However, I used a metal-scoop to scoop the soluble powder from Kelp4Less, and that got rusty from the sulfur.

I did not test the pH of Paul Neyron's pot, but I tested the pH of MiracleGro potting soil (green-bag), it's pinkish, or acidic, at 6.5 as others posted. After months of watering with my alkaline tap water, I tested that pot again, and it's slightly blue in red-cabbage juice, or alkaline .. so my pH 8 tap water increased the soil's pH.

I checked many sites on gypsum whether or not it lowers soil pH. Some sites says "yes", some sites say "no". So I tested it: I put more gypsum (calcium suifate) on some rose bushes before our week-long rain.

The dark-green ones that like alkaline soil: Golden Celebration, French Romanticas & Meilland DIDN'T LIKE the excess gypsum: leaves became thinner, and droopy. It's very much like the time I put too much sulfur on Sweet Promise ... leaves became thinner, more droopy.

Roses with musk or multiflora parentage that prefer acidic soil, LIKE gypsum. Excellenz von Schubert, a hybrid musk, does well with added gypsum, so does Annie L. McDowell. Austin Mary Magdalene likes gypsum, its bloom lasts 4 days in the vase, compared to 2 days in the vase from last year.

In my pH of 7.7 clay, most Austins bloom better with added acid, except for Godlen Celebration, Pat Austin, and Evelyn which are healthier in alkaline soil.

University of California Extension chart in the below link listed 1 ton of gypsum as equivalent to 5.38 ton of sulfur. It also listed 1.09 ton of Ferric Sulfate as equivalent to 5.85 ton of sulfur. I already tested Ferric Sulfate on my azaleas and rhododendrons in my soil pH of 7.7. It's a DISASTER, leaves get brown burnt from the acid and high iron.

The below table of University of CA is also useful if you have acidic soil, it lists what type of liming materials used, and how much to raise to neutral pH.

Here is a link that might be useful: Changing pH in soil by University of CA

My soil pH is 7.7 .. I was concerned that the lime added by the stable to their horse manure might make my soil even more alkaline. I asked the chemist in the soil forum if lime is mobile, he said, "No, lime stays put where applied."

I did more research and found hydrated lime added to tap water is unstable, and quickly raise soil pH. Lime exists in many forms, and the mobility varies. Here's the info. on lime, slow or fast means the rate of pH increase:

Equivalent Calcium Carbonate pH change

Dolomitic Limestone 70-95 Slow 50 Also a source of magnesium

Ground limestone 70-95 Slow 50

Hydrated Lime 140 Fast 20 Hazardous, difficult to apply

Pelletized Limestone 70-95 Fast 50 Easy to apply, more expensive

Hydrated Lime in tap water is the killer. It binds with potassium, phosphorus, iron, making nutrients less available. When I water roses with pH 8 tap water, roses are pale, and don't bloom. I have to fix my water by adding gypsum (calcium sulfate) which neutralizes the bicarbonates in tap water, and releases nutrients.

Below is Samaritan floribunda rose, picture taken during our 2 weeks of dry and hot temp. above 85 degrees. It's dark-green and blooms well if I fix my tap water with calcium sulfate (gypsum):

This post was edited by Strawberryhill on Mon, Sep 16, 13 at 11:54

Cactus Joe in PNW posted the most deep, vibrant pictures of Austin Roses: Deep yellow Jude the Obsucure, deep pink Eglantyne rose. He put all the info. on how he did that in his Gardenweb member page. Thank you, Catus_Joe, for sharing your experience, much appreciated!

Here's an excerpt from Cactus Joe on how he grew his roses in container.

1. POTTING UP CONTAINERS
Growing media: I use Sunshine #4 soilless potting mix.

To this I add water absorbent polymer crystals (according to instructions), 3 fistfuls of bone meal to every 15 gallons, Osmocote (according to instructions), and 1 part in 3 of composted bark mulch.

Feeding: I provide this with soluble fertilizer (Miracle Gro) at least once a week later in the season - usually starting from July (the Osmocote I use has an average release time span of 4 months)).

The containers are mulched. My experience is that a single lapse in allowing the growing media to dry out could set the plant back as much as a months growth!

Keep Cool In The Heat

Excessively high temperatures in the growing media likely impedes growth. I get better results by taking the effort to shield the containers from being heated by the sun in the middle of summer. (I have measured temperatures as high as 50-60 degrees celcius in containers exposed to direct mid-day sun in the summer!)

Good drainage is also vital - excessive water retained in the bottoms of the containers has caused problems for me with containers 3 gallons or larger. For containers of these sizes, I put some rocks, bits of bricks, whatever I can get my hands on over the drainage holes, and use a piece of landscape fabric over the rocks.

My aim is to get the plants from little whips in 3 inch pots at the start of the season to root balls that will fill out 3 gallon containers by the end of the season." Cactus_Joe

*** From Strawberryhill: I agree with what Cactus_Joe wrote. Last year I had 24 pots on my patio, this year I'm down to 16 pots, which I planted in the ground before winter hits. Same goal: to grow roses from band-size into 3-gallon solid root-ball for the ground.

His putting bone meal makes sense, since bone meal provides calcium essential for root-growth. I agree with Cactus_Joe in putting rocks at the bottom of the pot for heavy rain areas like mine and his PNW. This step is not important for dry CA.

My best result with pots was when I used Jungle Juice Organic Potting soil, with composted pine bark for best drainage, it also has slow-released fertilizer. Then I mixed 1/2 cup of Jobes Organic Fertilizer for tomatoes NPK 2-7-4 (with bone meal), plus beneficial microbes.

Then I put a tiny-bit of granular gypsum (calcium sulfate), plus sulfate of potash on top. I don't put chemicals inside the pot, since the young roots can be damaged if in direct contact with chemicals.

I was too lazy to soluble-fertilize, just my tap water at pH 8. Below is a 7-months old rose grown from seed, a Yves Piaget child with the above technique:

Here is a link that might be useful: Cactus_Joe's member page of Gardenweb

This post was edited by Strawberryhill on Sun, Nov 17, 13 at 19:08

I checked on many sites as to what to put in the planting hole. "For starters, rule number one is no fertilizer or compost around roots. This is the biggest problem causing losses of bare rooted roses. It keeps too much water around roots and the roots don’t spread. "

My garden of heavy clay differs vastly from Columbus Park of Roses in Ohio, with sandy soil. Peat moss glues up with my alkaline clay soil, but it's GREAT for sandy soil. The Columbus Park of Roses in Ohio with 11,000 rose bushes stated how they fixed their soil "The entire area of 13 acres had sandy loam topsoil to a depth of 11 ­ 15 inches ... All beds were excavated to a depth of 24 inches. The existing soil was removed and mixed with imported peat moss and commercial fertilizer."

University of Colorado is right about fixing clay with fibrous & woody materials, and fix SANDY soil with fine particles like peatmoss & compost & water-retentive additives (turface, Napa, kitty-litter, etc.). Thus "Hugel gardening" with tree branches at bottom, then wood chips & soil, and smallest particle like manure on top works well with clay soil.

Here is a link that might be useful: Epsoma Tomatoe-Tone NPK 3-4-6

This post was edited by Strawberryhill on Fri, Jun 13, 14 at 18:24