This blog is contributed by Mandi Atkinson, former garden curator at Lan Su Chinese Garden in Portland, Oregon.

I was reflecting earlier this afternoon about pests and diseases with mums and I wanted to elaborate on the operation at Lan Su Chinese Garden in Portland, Oregon, and why I think that I was lucky in terms of pests with my mums for that operation.

Each year, after we disassembled the display, we took all the potted plants back to our greenhouse and cut everything back to about 6 inches and all plants were sorted.  Leaves were stripped to prevent botrytis and plants were only watered once or twice during the winter months.  I was always careful not to overwater the plants while they were at rest. When plants looked dry, I would always lift the pot to see if it needed water. We started taking cuttings from our plants as early as the last week of February and into May.  Once the new plants were rooted, all mothers, aside from two mothers, were discarded, or donated.  I would only keep two mother plants due to spacing at our greenhouse and just in case something catastrophic happened.  When all cuttings had strong roots and were upgraded to larger pots, I removed all old mothers.  (Isn’t it sad that at a time where mums were so rare in abundance, I was in Portland throwing them away or giving them away because I had so many.)

We always displayed newly rooted cuttings at Lan Su because that was the traditional way that the exhibition mum growers did it and it’s also the same method that Longwood would do it.  From what I had been told, was that new cuttings would always produce larger, more robust flowers if fertilized in a timely fashion, pruned, and disbudded accordingly.  I do think that starting fresh each year with new cuttings and with fresh soilless medium each year also gave me an advantage with pests and disease because the soil was sterile and their final growing place (outdoors) was free of plants for the whole winter.

I also want to add that when I moved on to run my own operation, I was propagating new plants every year to build the plants that were in high demand.  In 2022, my last year growing flowers, I repropagated my entire greenhouse so that the growth habit was more predictable and easier to prune.  I also felt that the flower size would be larger on a younger plant.   I also noticed that in my collection, the stem seemed to be thinner on the older mother plants.  I think that all flower farmers would benefit from repropagating their own collection at the minimum every 3 years and maybe rotating their collections for pest and disease purposes if they can.  If you need tips on propagation techniques get Ivor Mace’s online book and pay close attention to the humidity and below-ground heating requirements.  I did this and had nearly a 99% survival rate and at that time I was working with trickier cultivars.

Lastly, I want to stress about how much fertilizer one applies to their collection.  I only fertilized at Lan Su 2 times in a season.  When I was growing at Rays I only fertilized twice as well.  What I learned in my 9 years of growing at Lan Su is that unless you want the blooms that are larger than a basketball, there's no need to apply that much fertilizer.  

Here is a link to the Concentrates Fertilizer mix that I’ve used for years: 

https://www.concentratesnw.com/?product=concentrates-purpose-fertilizer-5-5-3-organic-20

And a link to the soil that I would use every year when I was growing in a pot:

https://pro-gromixes.com/portfolio-item/pro-gro-5-f-blended-potting-soil/