Winter edition, RHA Newsletter

The main symposium topic for the Winter edition of the Newsletter is Potting Media. I chose this topic because I thought it would be timely for those of you who will soon be potting seedlings from 2007’s crosses. So far, you have not sent me any articles on the subject.

I need your thoughts and your experiences to make the Newsletter worthwhile for us all. If you want to think of this topic as writing a review or consumer’s report on one or more media, that may be a good way to go about it.

Not everyone starts seedlings under fluorescent lights, but I do, and I know that the faster I can get the seedlings to the blooming stage, the faster I can decide what to keep and what to get rid of. A seedling that under good conditions (good medium, good lighting, etc) might bloom in 5-8 weeks (depending on petal count and height) may take 10-12 weeks to bloom with a poor medium–and may not bloom until it goes outdoors in the spring–so it really is important to know what works best, just so I can make the most efficient use of space and energy. And if you are lucky enough to have a greenhouse, chances are that your space there is not unlimited–and in most parts of the country greenhouses cost money to heat at this time of the year.

Some of you may have some horror stories about potting media which looked good but didn’t give good results. Fine. Tell us what happened. Sometimes we need to know what to avoid–and why to avoid it.

If there is a mix that works well for you all the time, maybe it will work well for others who have the same or similar conditions. Your success can contribute to the success of others, and we’ll get better roses for all of us.

Not all commercial potting media are available in all regions, but if you use a good regionally available mix and can tell us what is in it, we might be able to find a similarly good medium elsewhere. By sharing our successes and failures, we can help each other.

I recall an RHA Newsletter article (1970’s, I think) in which Joe Winchel described how to make what he called “super soil.” I didn’t have the conditions to make that mix, but I saw his roses, and I know it worked well–VERY well. Tell us about your “super soil” if you make your own mix.

I myself have tried a number of different brands of commercial mixes, not always with good results, and I will write something about my experiences. I hope you will do the same.

Please send me your newsletter contributions as soon as possible. I hope to get enough articles by January 15 to get the Newsletter together. If you have questions about what might be appropriate, just drop me a note and I’ll respond promptly.

As usual, I’ll be happy to have articles on any subject you find interesting, so if you have an article about potting media and an article about something else, I’ll be doubly happy to hear from you.


Here is just one paragraph from one of my articles.

For beginners I suggest to read the whole article !

“Making Miniature Cuttings from Cuttings, from Cuttings…”

(The Primitive Way)

(first published in the Rose Hybridizer’s Association newsletter in summer 1995)

  1. I am now using a special, ready made, commercial planting mix which comes in bales like peat moss. I believe this mix has made the difference in getting 100 % rooted cuttings. It is called " Sunshine Mix Aggregate Plus #4 ". It’s major components are Canadian Sphagnum Peat Moss, Perlite, Dolomite Limestone (pH adjuster) and a wetting agent. In Canada it is made by “Fisons Horticulture Inc.” and in the US by “Sun Gro Horticulture Inc.” [Web site:]. My damp-off losses are way, way down to only 2-3 %, some varieties 0 %, since I now use only this mix for all my seed germination and for potting up my seedlings.

George Mander


Also go to my Rose Gallery page and click on :

Own Root Cuttings Setup Gallery with detailed comments and info for each of the 30 images.


Correction about my article:

“Making Miniature Cuttings from Cuttings, from Cuttings…”

I just got the NEW RHA disc a week ago and checked for the article.

It’s not in the Summer edition, but in the Spring 1995 one.


Hi Peter,

I have been hybridizing for about 15 years and I’ve gone through several mixes for seedlings but for me in the Pacific Northwest this works best:

1/3 Peat Moss, 1/3 Vermiculite, 1/3 Coarse Sand.

This mixture I plant the seeds directly into after stratification from the fridge. I plant outdoors, in direct sun around Valentines Day. I plant into a standard seed tray and place the tray on two- one gallon zip lock bags, next to each other filled with coarse sand, these fit perfectly under the tray. I place under the sand bags a heating pad covered in a large garbage or leaf bag set on LOW. This keeps the pad dry. I spray the tray daily with a watering system to keep everything very wet, even if its raining. I get about a 30% germination rate and transplant seedlings as soon as they are standing straight up…usually two days old. It is vital that you do not touch the root in any way, shape or form, this I learned the hard way. After transplanting into a nice potting mix I cover well with a vented plastic bag or place in the hot house (if you have one) and fertilize with 1/4 liquid rose food DAILY. By 6 to 8 weeks the plants will bloom. Regular care should be given after that.

After re-reading my posting it should read 1/4 strength liquid rose food DAILY.

Hope this helps some people.


Thanks to George and Jack for their suggestions. If you have something you want to send to me, you may use the link here by my name and put your suggestions/article in the email you send, or may send an email with what you have to say, either in the email or included as an attachment, directly to peter.harris.g at (use an @ instead of the word “at”, of course). All suggestions are welcome.


Hi George, I drive to another town to pick up sunshine mix, thanks for all your info. Robyn

These are a few things that have worked well for me.

I like to use Pro-Mix and have a local supplier. It is also a soilless media that contains peat, perlite, and vermiculite I believe. In the past I used another mix that has small ground bark within it because of a suggestion that it works fine and is cheaper. I lost flats of seedlings pretty fast. Talking with the sales person next time he said there has been some disease trouble with that mix that has been traced back to an incompletely composted batch of bark in Georgia used in the mix. I’m really protective of my seedlings ever since and just use ProMix as I pot them up initially in 6 packs. After that I transplant them into ProMix or ProMix with some mineral soil added (about a fifth or quarter). Mineral soil will help buffer the pH and prevent as much spiking. I have city water and they pump sodium hydroxide in it to raise the pH and prevent metal pipes and hot water heaters from corroding as fast. I add the appropriate amount of acid to my water before I water my plants too to take the water pH from close to 8 down to about 6. I have five gallon buckets I fill in the sanitary tub in the basement and then carry it over to the plant stands and use a plastic cup to dip into it and water what I need to.

I also have found that I need to be very careful about fertilizer as well. The ammonium toxicity problems I had spurred the nitrogen article I wrote for the ARS magazine a few Augusts ago. There is a natural progression from urea to ammonium to nitrate. The higher the temperature and more active microbes are the quicker the transition goes. Water soluble fertilizers like Miracle Grow and others rely on this transition and supply nitrogen as urea and/or ammonium. Under warm conditions that is fine. Unfortunately, ammonium levels cannot build too much in plants before there are toxicity issues. Nitrate can build more before there are problems. The basement is cool (55-60F) and I wasn’t getting the conversion from Miracle Grow and got ammonium toxicity problems even though I wasn’t using what seemed like excessive amounts of fertilizer. I switched to a nitrate based fertilizer. There are products like dark weather feed that takes this into account and is sold to and used by especially greenhouses in the North during the winter months.

I also find that humidity is a big factor for me too for survival. I germinate seeds in plastic baggies with moist peat moss. After I transplant them up (they are relatively small yet with cotyledons just expanding) the growing point may abort due to drying out. I put clear plastic domes over my flats until there are two true leaves and then take it off and things are fine. I found that if I have the lid offset so the short end is hanging off the edge a bit and there is a little gap (like a half inch), there is still enough humidity to help them get started better, but not too much moisture that they become distorted and difficult to wean the humidity from.



my seeds are in regular potting mix this year. i only have 70 seeds and most are op. they are in the fridge and are comming out soon and put under lights .

this year i am going to do everything by the book! right soil mix, pick hips when

ready,and put them in soil before they go into fridge because i was told its better then the paper towel treatment. then they will go under my lights. and cross my fingers!

I know many hybridizers do not keep seeds that do not sprout within a certain time frame, some to insure vigor, but I had quite a flush of bloom from a flat that had been ignored and not watered (but not discarded.) I happened to notice little seedlings and watered and got more germinations. This was the 2nd year after sowing. Potting soil was nothing special. Robyn