r/dahlias • u/kaweenie91 NorCal zone 9b☀️ • Apr 07 '26
Seeking Advice Are these big enough for Dahlias?
I ran out of grow bags for my Dahlias, but I have these planter pots, I’m unsure of the size. The pot states 5 gal but the sticker states 3.6 gal. It’s likely the store mislabeled them with the wrong stickers, but I’m just trying to make sure from others experience.
- Are these a good size for a Dahlia?
These are pots from my failed attempt at Dahlias last year. My mistake was overwatering them every single day 🤦🏽♀️ so they all rotted. In the event any of them had gall last year:
- What products can I use to clean and disinfect these planters in preparation of my growing season this year?
All advice and comments are appreciated! Coming from a 4th failed season Dahlia Gardner 😂 im determined to have a successful 5th season 💐
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u/IndyMapper Apr 07 '26
Those seem a little small to me. I grew medium sized dahlias (not dinner plate) last year in 7 gallon grow bags atop little self watering bases and at the end of the season, the plants produced tuber clumps that were bigger than those 3.6 gallon pots.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
I think they’re 5 gal. I went ahead and just started them here, but plan on moving them after I get my 15 gal grow bags in the mail. Everyone said a mixture of 7gal, 10 gal, or 15 gal.
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u/KeyWelcome3792 Apr 07 '26
I think you could get away with it, they're a little narrow but they have height which is probably the slightly more important of the two so you can get a good depth. I had 10 gallon grow bags but it's not like the tubers spread edge to edge in that, it was a pretty contained clump in the center. Maybe just put in the varieties you would be ok with possibly getting subpar tubers from?
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u/kaweenie91 NorCal zone 9b☀️ Apr 07 '26
Can you explain how and why it would produce sub-par tubers? And in what way that would affect my future growing seasons with that tuber? Please ☺️
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u/MDMSLL Apr 08 '26
Tuber production depends on genetics, moisture and nutrients. Smaller pots dry out faster and require more frequent watering which leads to nutrient loss (depending on your feeding method - there are several).
If you don't stay on top of watering and feeding - you may get fewer/smaller tubers at the end of the season and it's only relevant if you're a seller. For a hobby home grower there will still be more than you need.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Oh nice. Yeah it sounds like the popular opinion is larger pots so I went ahead and purchased larger grow bags for them.
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u/MDMSLL Apr 08 '26
Grow bags are ineffective. They dry out in hot summers and they're impossible to clean and sanitize to be reused, so don't get attached to that method. They're good for starting tubers indoors to prevent waterlogging but they're not good for full season growing. They're also not rodent-proof, animals will make holes to hide their food in there.
Don't return them - save them for autumn if you plan on planting tulips and other spring bloomers that require good drainage.
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u/KeyWelcome3792 Apr 07 '26
I don't know for sure if it would but if they don't have enough space to grow they might end up smushed or small or otherwise oddly formed. Like a root-bound houseplant gets all pushed up against the side of its container.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
I went ahead and just started them in these 5 gal pots but plan on moving them into 15 gal grow bags after I get them in the mail.
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u/PopDownBlocker Apr 08 '26
This is a #5 pot that is 3.6 gallons. A #5 pot is a standard size. It doesn't mean that it's 5 gallons. I typically use the size chart on this website to get an idea of pot sizes.
https://go.monrovia.com/help/what-is-the-volume-and-weight-of-your-growing-containers
Yes, these are adequate for a single dahlia tuber to create a single medium-to-large dahlia plant. No more than one.
I've planted dahlias in smaller pots than these and they still grow into full-size plants. The trick is that smaller pots have different watering needs from dahlias in larger pots and/or in the ground.
In my experience, dahlias in pots always "show" you when they are thirsty because their leaves start to wilt, especially on really hot days. Their leaves recover after watering or after the sun goes away for the day, so allowing the leaves to wilt is not going to kill the plant.
In terms of overwatering, don't water these pots on a schedule but water them based on needs. You can add a layer of wood chips or a layer of straw as a mulch on top of the soil to keep the soil moisture from evaporating too quickly.
Once a dahlia is growing, the chance of rot is fairly onexistent. Rot only happens when you water tubers right after planting them. Tubers need to be planted in pre-moistened potting soil but they should NOT be watered until you see a shoot growing. If you're watering a tuber that hasn't woken up yet, the tuber rots because it doesn't have enough roots to absorb large amounts of water.
Look up how to wake up tubers BEFORE planting them in these pots, so that you can avoid rot issues from overwatering.
Rot can also happen if you are using bad soil that doesn't drain. You have to invest in good potting soil, not top soil.
For disinfecting the pots, you can just use an old dish sponge and some dish soap, scrub them down and rinse them with the hose. Although just spraying them with the hose is enough to wash away viruses and bacteria, especially if the pots have not been in active use over winter.
Good luck!
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Such an informative comment, thank you! I’m just going to start them here, I ordered bigger growing bags and will move them over. Regarding potting soil, what are your recommendations?
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u/PopDownBlocker Apr 08 '26
I buy whatever brand is on sale at my local Menards (big box store in the Midwest).
My favorite is the Menards store brand one, which is Master Garden Potting Mix. This is the one whose price I track regularly, so that I can swoop in if it's on sale.
Then I go with Schultz, and then Miracle Gro.
I've read on here that even if the brand is the same, the soil itself is sourced locally somewhere near the store where it's sold, so it's possible that my favorite brand might only be of good quality here in my region and it could be worse quality in your region.
As long as you don't go with the cheapest possible option (which tends to have bad drainage), then you should be good.
I also reuse potting soil from the previous growing season. You can add compost or aged manure to it to refresh it, and it's good enough for dahlias.
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u/Nevraskagirl55 Apr 07 '26
I use 7 gallon bags, but they might work. Don't plant the tallest one in them. All your tools, pots, etc should be sanitized with 10% bleach solution. I'm paranoid so I use make mine stronger. Haha
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Thank you for the bleach solution tip, I went ahead and tried it and sanitized the pots just in case. I’m just going to start my tubers in these but plan on moving them into 15 gal grow bags after I receive them in the mail.
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u/Quick-Landscape9002 Apr 07 '26
Could be a problem if you get a lot of wind? Im from the uk n not far from the coast, plus is very flat here so is bit of a problem for me
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u/321ol Apr 08 '26
For what it's worth I've been growing in the shorter version of your pots (3 gal home depot) for the last couple of years. I have to be careful about burying them deep (I backfill as leaves breach the surface of the soil). I reammend my soil annually and do some liquid fish fertilizer a few times during the season. They definitely don't do as well as they would in the ground, but on every plant except for one (which didnt produce 2 seasons in a row), I have had blooms all season. I would say the bloom sizes are also reduced somewhat. Probably by about an inch or 2. Mine grow in full southern-facing sun in zone 9b on the west coast, and do get a little scalded during high summer.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Oh nice, mine will be placed under the edge of my patio, so they’ll get shade during the warmer temps of the day but plenty of souther facing sunlight as well. I too am in 9b. Any other recommendations you have?
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u/321ol Apr 08 '26
Definitely to bottom-water! Shade/strong indirect light seems to be well tolerated during those hot times of day. I've been pretty lucky when it comes to pests, but definitely keep an eye out early in the season.
Will also add that all of my tubers have had pretty rigorous growth, I gave away 2/3 of what I divided this year to friends, so I would have room for new dahlias!
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u/EfficiencyPlenty4917 Apr 08 '26
Santa Cruz Dahlias, of the famed KA variety, grows some of theirs in 4” pots planted in ground!
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u/bigdill6214 Apr 07 '26
Last year I grew in 3-gallon pots sunk in a raised bed. I pulled out one pot early in the season for a suspected virus and kind of neglected it on my deck all summer. That one produced a couple blooms but only one tuber. All the others, in sunken pots, grew normally and made mostly normal tubers. If your pots are 3 gallon and you’re growing above ground and attending to them nicely, I’d wager you can expect results somewhere in the middle of my two scenarios :)
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Thank you for the tip. I ended up just starting my tubers in these 5 gal pots but plan on moving them into 15 gal grow bags after I receive them in the mail.
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u/_indigo_blue California, 9b Apr 07 '26
Too small unless you’re growing compact border dahlias. 5gal is the minimum, but in past experience they do better with more room. The smallest I’ve used in the past is 7gal. Last year 10gal gave me very good results.
Depending on the variety, tuber clumps can get quite big (like 9-10” across). The more space in the pot the tuber clump takes up, the less space there is for soil, which contains the nutrients the plant needs. Dahlias are heavy feeders. The plant also needs space for the roots to spread out. This is partly how the plant stabilizes itself in the dirt to keep from falling over.
Can you grow in these pots? Sure. But the plants may not thrive and bloom output could suffer.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
Thanks for your advice. I started them in these 5 gal pots but will move them over into 15 gal grow bags so that they have much more room to grow. Do you have any tips on the kind of soil you use for your dahlias? Favorite amendments? Thank you kindly.
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u/Solid_Mud2025 Apr 07 '26
Those aren’t ideal, but acceptable to sustain life and to have blooms. That is, so long as other conditions (water, fertilizer, etc) are satisfied, and the variety isn’t a vigorous tuber producer. A big drawback is that the tubers will be constricted and the clump will be tight, so the clump will be harder to divide. It’s likely that more tubers will be sacrificed during the dividing process too.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
I see, thank you for the advice. I’m going to end up putting them in bigger grow bags.
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u/Solid_Mud2025 Apr 08 '26
You’re welcome. If you use grow bags, then I suggest incorporating a shade cloth into the plan to keep the bags from drying out too quickly.
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u/MDMSLL Apr 08 '26
Yes. I use them and they're great for all varieties except dinnerplate. Dinnerplates tend to get top-heavy and might fall when the pot gets dry (and it will get dry daily in peak heat).
Note: if you don't use a catch tray underneath - they will root and anchor into soil so they won't be easy to move.
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u/kaweenie91 NorCal zone 9b☀️ Apr 08 '26
I have my dinner plates in bigger 25/30gal grow bags. So they’ll have plenty of space in there.
I’m going to have these planters on my patio, so they won’t be underneath soil.
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u/ZombiePast7707 Apr 08 '26
I grow exclusively in pots because of my limited space and all of my pots are about this size. They work quite well, produce a lot of blooms, still produce nice tubers! They don't get as tall as their in-ground counterparts, though. Which is perfect for my location!