This post was contributed to by Abigail Wiesner, Drs. Sarah Jandricic, and Chevonne Dayboll.
As we feel temperatures rising, summer is on its way – and so are garden mums! This post has updated information to help you optimize your irrigation, fertilizer, pest management programs and more in garden mum production.
Only looking for specific info? Click between sections:
Irrigation and Fertilization
Given the large acreage often occupied by garden mums, your watering strategy is one place you can look to save money and maximize water efficiency.
Overhead irrigation by boom or sprinkler system is only efficient with plants placed tightly together. Canopy sizes in the later months of production may make this impossible, especially if you choose to go with final spacing when pots first move outside. Often plants are left too dry or too wet when watered overhead.
Drip lines are only efficient if they work properly! Don’t “set and forget” – monitor for kinked lines, clogged emitters, and loose connections. Be in-tune, know your application volumes and irrigate based on crop needs and weather patterns.
As with irrigation, it’s important to remember 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 fertilizer types for garden mums. Some growers prefer water soluble fertilizers for increased control and benefit of a quick change if needed. Others choose controlled release fertilizers (CRFs), incorporating into the growing media and letting their irrigation schedule ‘do the work’. Check out Table 1 below for quick tips when using these products.
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 |
The amount of nutrients staying with the plant are usually highest when controlled release fertilizers (CRFs) are used with carefully monitored irrigation. They are usually lowest when water soluble fertilizers are applied in high volumes (resulting in a lot of irrigation running through pots) and irrigation efficiency is low. To keep the fertilizer where you want it, it’s important to irrigate only enough to saturate the pot. Both formulations have their pros and cons, so make sure whatever you’ve chosen is easily managed.
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 own irrigation efficiency.
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 have high P as well, but double check your fertilizer labels to ensure that 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).
While not commonly discussed here in Ontario as an issue, our neighbours to the south have dealt with and prepared excellent materials addressing this issue. 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.
Pest Management
Summer production for a fall crop can be challenging but planning ahead with a pest management program can help you prepare. The good news is that garden mums grown outdoors simply don’t get the same pest pressure as pot mums in Ontario.
Why? A lot of this has to do with natural enemy populations from surrounding agricultural lands that seem to keep a lot of pests in check. To conserve these free biocontrol agents, avoid spraying if you can. If you DO spray, do yourself a favour and chose something that’s compatible with beneficials so you don’t end up with a bigger problem on your hands from secondary pests.
Table 2: Suggested pest management program for most problematic pests, grouped by week after transplant.
| Week after transplant | Suggested Program | Target Pest/Disease | Tips |
| Propagation | Nova (mycobutanil) | Chrysanthemum white rust | Propagation growers often use Nova as a precautionary application |
| Transplant | Dips in BontaniGard WP | Thrips – (Western Flower Thrips and Onion Thrips) | Garden mum cuttings do not tolerate oil dips (see more details on dips in this post on spring crops) |
| 1-9 | Predatory mite sachets (Amblyseius cucumeris) Beauveria-containing biopesticides (BotaniGard, BioCeres) Mass trapping cards | Thrips | For indoor-grown garden mums: Sachets at 1 per pot are best for long term protection especially given issues with penetrating canopy for soil drenches. More information about mass trapping with cards here |
| 10-16 | Atlus (flupyradifurone) Beleaf (flonicamid) | Aphids Tarnished Plant Bug (also known as Lygus bug) | For outdoor grown garden mums: Typically seen in late August/September – walk the crop regularly and make an application only when insects are detected Beleaf – soft on beneficials, can be applied via drench through irrigation lines and it’s cheap! Registered for both aphids and lygus bug |
For more product information check out Ontario’s Crop Protection Hub, a new one-stop-shop for pesticide information for greenhouse crops!
Other pest considerations:
Chrysanthemum white rust – while it is a quarantinable disease, it has only been detected in Ontario once in the last decade thanks to regulations requiring plant material be sourced from white rust-free facilities. Since other, more common diseases like powdery mildew can look like white rust, it’s always best to schedule your inspections with CFIA a few weeks out from shipping, if possible. This way, if any suspect plant material needs testing, you have time to be cleared well before your planned ship date. Fusarium, Pythium and Rhizoctonia are more common, but generally aren’t big issues in Ontario production. If problems develop, a good guide to disease symptoms and cultural management in garden mums can be found here.
Japanese beetle. While generally not a problem on garden mums, recall that all plants produced outside from June 15 to September 30 need to be treated for JB if you plan to export or ship to a JB-free zone. See this post for details.
Leafhoppers. These can fly in from the same surrounding agricultural lands as your free natural enemies and can seem like an issue since they jump around plants a lot as you pass. The good news is they don’t seem to do any real crop damage. Resist the urge to spray, and simply make sure your workers give plants a good shake to dislodge any adults before packing.
Additional Resources
Flowers Canada research update – irrigation and fertilization trial with chrysanthemum and hydrangea
Culture Guides by Ball Seed and Syngenta Flowers
It’s Time to Fall for Mums by Nancy Rechcigl – how to establish an agronomic program
Its Time to Fall for Mums by Grower Talks – audio file accompanying the previous article
Back Pocket Grower calculators – calculators for fertilizers, substrates, crop budgets, climate, and water quality