Excellent multidisciplinary query!

Hi Ryan

What part of the country are you? That would help us determine how big the bushes might get. At 22” wide and only ~10 gallons, we’re talking about some rather shallow pots, so moisture evaporation might be an issue. I think the roses would be fine for two or so years if kept moist, then they’ll want something bigger.

I like These lightweight planters. I’d estimate they are closer to 20 gallons.

Thanks for the reply. They are 15.5” wide and 20.7” deep.

I’m in zone 10a but it’s more temperate than the zone suggests. I’m more worried about evaporation from wind since the 2nd floor will be slightly windier than ground level. I have mulched the top pretty heavily and so far moisture retention is good but the highs are still only in the low 70s.

I’ll take a look at those planters, at first glance they look like they’ll work in the future if I have to move up.

Forgot to mention the other set of containers are 20” wide and 17” deep. Those are what the hybrid teas are planted in. The floribundas and a 24” patio rose tree are in the more vase-like 15.5” wide container.

Vase-like (substantial depth, for the volume) is helpful if soil drainage isn’t ideal.

Ryan M, I grow ~200 roses permanently in pots. I generally use 15 gallon nursery pots, which work great for me. I'm in zone 9b/10a, coastal Calif. I crunched the numbers on your pots, and the first one you mentioned came out to being 16.9 gallons. The others you mentioned came out to 23 gallons. Both of which are plenty generous. The only caveat I would say is that of course you don't fill them to the top, and that if the diameter of the bottom of the pot is significantly less than the top diameter, there is less volume in your pot than I calculated. Always use the total volume to determine how good the pot is, since that's what is available to the roots.

Thanks Susan. I was look at the specs page for the pots I bought, and the volume was listed (in quarts) so I converted to gallons. They do taper—the 15.5” pots are tapered to a v shape quite significantly. The larger 20” width/18” height pots are much more squat with about 2.5 inches taper between top and bottom.

But web site is confusing and perhaps your math is more correct. The web site lists the “planter volume” at 44 quarts or 11 gallons. For as large of a container it is, it seemed small. But another measurement listed is planting capacity and it’s listed at 3.31 cubic feet of 20+ gallons. Not sure I understand the difference.

also, 200 rouses—awesome! Love Santa Barbara and it’s climate is very similar to my coastal LA climate so it gives me hope.

Hope your roses are doing well. I grew roses in pots on my stucco deck in OC (Irvine-Newport Beach about a mile from the coast) for about 18 years. It was really a challenge to keep them healthy, growing, and beautiful. My pots were terracotta, 24 inches in diameter at the top. Roses need a LOT of water and nutrients spring through fall. My best/easiest results were when I used a gritty-inspired mix, automatic drip watering TWICE A DAY in the summer, and Osmocote Plus CRF, with occasional hand watering with added vinegar to counteract the high pH of water from Irvine Ranch Water District.

Thanks for checking in. Fertilizing has been an issue I didn’t foresee. I was trying to fertilize with water soluble fertilizer weekly but still ended up some some nutrient deficiencies that I never fully diagnosed. It’s an interesting and sometimes frustrating challenge.

Osmocote Plus in pots has been so easy and effective here on top of the potting mix.

Thanks Sheila i recently switched to Osmocote (around a month ago) and it may be too soon to see a difference. I previously saw both a nitrogen and potassium defency in many of my pots. Watering actually hasn’t been too much of an issue—temperatures rarely reach higher than 78 here in my coasal California climate—so once a week deeply watering has sufficed. I’m wondering if I need to add vinegar to my water when watering.

Ryan, I wish I knew your water ph before answering that. Make sure you have good drainage holes in the pots. Elevating the pots on raised discs could help drainage too. Some of the complicated potions people try seem to do more harm than good.

I do know LA in general has pretty alkalnine tap water from what I have read including the water quality report for my area (average is 8.1) but I do need to test it myself.

The pots do seem to drain well enough, I water them until water comes out the bottom and it seems to be reasonably fast when it drains. I do wonder if my potting mix is too water retentive—watering once a week seems to go against what others’ experience is even in temperate coastal SoCal.

Ryan M, I'm extremely surprised that you only need to water your large rose pots once a week. I'm also in a coastal So. Calif. area. During the peak of summer, I water mine at least every two days, and if it's sunny all day and/or windy and hot, once a day (or day and a half). But most of mine are well-established, so the roots are filling the pots pretty much. Osmocote plus is great, but I usually use regular MiracleGro which I water by hand b/c I feel like I get better control, rather than the random release of nutrients from the Osmo, which depends on the temp and watering. Ideally, I'd apply the MG half-strength every two weeks, but since I have >200 large potted roses, and numerous other potted plants, I tend to do full-strength every four weeks on the big fellas. Both Osmo plus and regular MG should give you a great nutrient balance. My tap water is between 8.0-8.5.

Here's an example of my pots. I took this pic for a discussion about clematis, thus the fact that it is prominently featured! Click on the pic to see the whole thing to actually see my pots.

I too am surprised by once per week watering. I water pots daily here.

My potting medium is almost all Miracle Grow Moisture Control. Perhaps the pots are retaining too much water? Like I said water does run out of them pretty quickly after watering. They each get around 1/2 gallon of water which seems to be whats required to get water to run out of them. The pots are all mulched with compost and some cedar chips on top.

About 3 days after watering I find the top 1/4 inch is mostly dry but its still moist ”knuckle deep” so I only water weekly.

Only thing I can think of is that the compost has started going into the potting soil and its gotten too sludgy, but somehow it still drains?

JIm Putnam (Youtube former nursery owner) uses 50% potting soil 50% pine bark mulch for all shrubs in pots. I put a lavender in potting soil and it was never happy, no mater what I did...my veggies do great in potting soil.

susan9santabarbara what do you use for your potting soil?

Ann, currently I'm using Edna's Best potting soil, which is available at my local real nursery. My favorite "homemade" potting soil was a combo of Edna's and Kellogg's Patio Plus, but my local small box store stopped carrying the Kellogg's products when they became an Ace affilate a couple of years ago. The Patio Plus was more fluffy than the Edna's, and the combo of the two was great for me. But the Edna's only is fine.

Ryan, I've read a number of threads that indicate that the MG Moisture Control potting soil has too much of the water-retaining stuff, plus one report from a friend in OK. Which is why I haven't bought it at Costco when it's really cheap. But I have no personal exrperience with it.

I use Miracle Grow Moisture Control potting mix in all of my rose pots as well. I have found that it is possible to water once a week during the spring. Once the temperatures exceed 100F, watering twice a week is required for full sun locations to prevent much leaf drop, but Mel's Heritage and Cecile Brunner cl. were able to survive once a week watering.

The temperatures here so far havent’t gotten above 80. This week was our hottest yet and it was 79 and 80 every day. The plants are all still small—except for one rose that really shot up, none are bigger than 24” since they still first years. So perhaps the Miracle Gro isn’t to blame and watering weekly is still okay.

Regardless I do have a nitrogen defiency in many if not most of my roses. I’ve gotten a lot of good flushes, so I was not terribly worried for a while since I was awash in roses. But past couple of weeks I have seen a lot more yellow/brown leaves from nitrogen defiency. I was watering every other week with 1/2 strength Miracle Gro but switched to Osmocote after I had just gone through a potassoum defiency issue as well and decided the MiracleGro fertilizer wasn’t cutting it. In June i put in Osmocote and am watering in fish fertilizer so we'll see if thokgd look better in August…

I was reading a lot about container growing and getting the idea that maybe the potting soil needs to be suited to the gardener and the climate when I ran across a woman who has a plant watering service and youtube channel...she had a potting soil chart based on plant type and overwatering or underwatering tendencies....wow.....so interesting!

Ryan, that sounds good. Our weather here is much hotter than yours. We've had 24 days of 100 F or higher so of course I need to water pots daily here.