Garden Mum Refresher 2025: Managing Nutrients, Size Tracking, and PGRs
This post was contributed to by OMAFA’s Greenhouse Floriculture Production Specialists past and present: Kathryn Russell, Abigail Wiesner, and Dr. Chevonne Dayboll.
As we feel temperatures rising, summer is on its way – and so are garden mums! Although generally an easy crop, there are several tweaks you can make to help save headaches AND money. This post has updated information to help you optimize your nutrient management and growth regulation/tracking in garden mum production.
This post gives an overview of some tips and tricks for growing Garden Mums – if you would like more detailed information, have a look at the production guides from Ball Seed and Syngenta.
Only looking for specific info? Click between sections:
Fertilization
One rule to remember is that if nutrients don’t stay with the plant, they can’t use it. There are a few schools of thought when it comes to keeping fertilizer where it’s needed for garden mums.
Some growers prefer water soluble fertilizers for their ease of control and dosing flexibility. Others choose controlled release fertilizers (CRFs), incorporating into the growing media and letting their irrigation schedule ‘do the work’. To keep the fertilizer where you want it, irrigating only enough to saturate the pot is important. Both formulations have their pros and cons, so make sure whatever you’ve chosen is easily managed. Back Pocket Grower is a helpful tool that helps you calculate exactly how much fertilizer you will need. Check out Table 1 below for quick tips when using different fertilizers.
Table 1: Comparing Fertilizer choices for garden mums.
| Water Soluble Fertilizers | Controlled Release Fertilizers |
| – Higher risk for leaching – Fine tuning advantage for production needs (i.e. need to green up before shipping) – Volumes of irrigation applied greatly influence the impact |
– Choose the right product based on your irrigation methods, formulation and the release curve – Ask supplier to verify the product and rate against your production needs before incorporating |
Check out this previous post to read more about how to improve fertilizer and irrigation efficiency for outdoor mum and hydrangea production. This post also highlights how YOU can track your irrigation efficiency.
Are you worried you aren’t feeding correctly? Are you unsure if what you’re seeing is disease- or nutrient related? Check out this handy guide on Garden Mum diseases and nutrient deficiencies.
Size Tracking
While we’re on the topic of fertilizer and growth, we wanted to point out Ball Seed’s great tool to track the growth of your mums in a few easy steps:
- Save time by making a measuring stick: label a tomato stake in 1-inch increments and leave it in a representative plant.
- Find the tracking tool at Ball Mums (ballseed.com) – enter your current height, target height and ship date. The tool produces a graph. Print and post this graph in your growing area.
- When you check your crop, compare your graph to the lines still visible on the measuring stick and determine if your mums are too tall or too small.
- Make small adjustments to your liquid feed until you are back on track:
| Too Small? | Too Tall? |
| Raise P Raise NH4+ to stretch |
Lower P Raise NO3- for compact growth Lower NH4+ |
High NH4+ fertilizers usually also have high P, but double-check your fertilizer labels to ensure you’re using the correct forms of N.
Rather hear someone discuss this method? Listen to STEM’s 2019 podcast series with Dr. Will Healy Part 1, Part 2, and Part 3.
Premature Budding
Have you ever experienced premature budding? Also known as ‘crown budding? This is when premature flowering is initiated due to cold night temperatures (<15-18°C). Check out these Ball Seed Tech Tips 1 and Tech Tips 2 for more details on how to manage crown budding.
A few summarized tips:
- Avoid low-temperature stress. While indoors in late May and early June, keep an eye on weather patterns and adjust nightly temps if needed.
- Avoid other stressors: A happy, healthy, well-balanced plant will be able to withstand more temperature stress than a ‘hungry’ plant, for example.
- Corrective nutrition: Mums respond well to fertilizer adjustments. If you catch premature budding early enough, you can ‘kick’ the plants back on track with an aggressive fertilizer program.
Plant Growth Regulators (PGR)
PGRs can be invaluable tools for controlling plant size, premature budding, and finishing times in greenhouse crops. However, these chemicals can be tricky to get right and may cause stunting or delays if used improperly.
It’s crucial to conduct your own on-farm trials before implementing a crop-wide spray program. The efficacy of your PGR drench or spray depends on numerous factors, including plant variety, day length, light intensity, and temperature. Therefore, you must trial each variety individually and consider the variables of the growing environment when determining when and how much to spray. Multi-year trials are essential to gaining a complete picture of how PGRs can work with your crop.
For a helpful outline on how to conduct on-farm trials, download the slideshow below or take a look at the additional resources posted on the ONfloriculture blog.
Some PGRs to try:
Table 2: Comparing PGRs for Mums
| Commercial Name* | Active ingredient | Uses |
| B-nine / Dazide | Daminozide | – Controls stem elognation |
| Florel / Collate | Ethephon | – Promotes flower bud abortion – Promotes branching |
| Bonzi / Piccolo | Paclobutrazol | – Controls stem elongation – Can help control finishing time |
*Commercial names listed in this table may or may not be registered in Canada. Always consult the product label before purchase or use.
Florel can be applied during long-day production to keep plants in a vegetative state. It’s useful for delaying bud initiation if you unexpectedly experience several cool nights after moving plants outside. Florel works preventatively, so you must monitor long-range weather forecasts to use this spray effectively. Remember, Florel is a growth retardant, so you may need to adjust your grow times accordingly. As always, trial before committing to spraying your entire crop.
Bonzi is particularly tricky to use on garden mums – but don’t let that shake your confidence! It can be sprayed or drenched in the crop to reduce stem elongation and help control finishing times. It is typically applied after the plants are established and moved to outdoor production. This product has a wide range of label rates, and using it improperly can significantly stunt or delay your crop. It may be easier to gain control by doing more frequent low-rate applications rather than just a couple of heavier ones. It is also convenient to drench in if your mums are outside and on drippers; this way, you can easily control how much product each plant gets.
The bottom line here is: give PGRs a try! If you are currently using non-PGR methods to control the growth of your crop, that’s great! Maybe start by using a small sample of your crop to trial PGRs and see how the results compare to your traditional methods. There is always room for improvement and cost savings when it comes to growing.
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