Little Gem magnolias in San Diego yard?
TLDR: Can I plant Little Gem magnolias in an area that is long but only 4 feet wide without damaging surrounding concrete / retaining wall?
Full saga with many additional questions:
I recently bought four Little Gem magnolia trees in 24-inch nursery boxes (still waiting for the 4th to arrive). They are already about 10 feet tall measured from the soil line, which is already as tall as I was led to believe they would get (I no longer believe this to be true).
I bought them because I am trying to shade the slider / window facing 140 degrees SE. At this time of year especially, the sun comes over the house in the morning at the perfect high angle to hit the windows and get behind any blockers that aren't right up against the house (see red dot to represent sun in the pic). But in general, I would like year round shade as much as possible on that side of the house. I want plants rather than awnings for various reasons. After lots of research, chatting, and nursery conversations, I decided little gem magnolias were a good option. They are robust, stay reasonably small, don't drop a bunch of garbage on the ground, and make great shade. The issue is that in their current size, they need to be basically next to the house to create any shade where I want it. I am aware I will need to wait a few years for them to be really useful, but I want to plan / minimize that time as much as possible. Partly, I am trying to decide whether to plant them in large containers near my house for the next several years, plant them in the ground now, or reconsider the plan entirely (some other type of plant). I would especially appreciate advice from people who have grown Little Gem magnolias in Southern California.
My questions are:
- How much open ground does a Little Gem actually need?
The possible planting areas are surrounded by concrete (see pics), so I am concerned about roots eventually lifting or cracking it. In the pic with the 3 trees, the dirt area is 7 feet wide where the far tree is, and only 40" where the near tree is.
Chat suggests that I need almost as much root area as the canopy to support the tree. At the same time, I see many mature full-size magnolias around my neighborhood planted in narrow strips between sidewalks and curbs. Some have trunks around 18 inches thick and canopies roughly 30 feet across, yet the surrounding concrete appears undamaged. In some cases, the visible soil strip is only about 3 feet wide (but is long in one direction).
Does a Little Gem need an open planting bed approximately as wide as its eventual canopy, or can it grow successfully in a much narrower strip or opening? Does it make a difference whether the available soil is a long, narrow strip versus a small square opening surrounded by concrete?
For those who have planted one near paving, how close is yours to a sidewalk, patio, driveway, foundation, or curb, and have the roots caused any damage? I would really like to avoid damage to the retaining wall in the background, or the sidewalk / fence concrete.
- How large can one realistically grow in a container or out?
Because these trees are already about 10 feet tall, I am trying to understand how much larger they might become in a large pot vs in the ground.
I have been looking for containers approximately 30 inches in interior diameter (see pic, but one size up), large enough to accommodate the existing 24-inch square root balls (same square shape). Has anyone kept a Little Gem this size in a container? How tall and wide did it eventually become, what size container was it in?
- Can a Little Gem remain healthy long-term in a pot with root maintenance?
Could one live for many years in a sufficiently large container if it is periodically removed, root-pruned, given fresh potting medium, and returned to the container? Or do Little Gem magnolias eventually decline in containers regardless of that maintenance? For anyone doing this successfully, how frequently do you inspect or trim the roots, and what problems have you encountered with watering, drainage, heat, wind, or root binding?
- Could I plant them in the ground later?
Part of the reason I am considering containers is that I could initially position the trees closer to the house, where they would provide shade sooner. As their canopies widen, I could move them farther away and eventually plant them in their permanent locations. Is it realistic to keep trees this size in containers for perhaps several years and then plant them in the ground? Would that create major root problems or transplant shock later? I understand that the trees and containers would become extremely heavy and would probably need to be moved with equipment. I am primarily asking whether the plan is horticulturally sound.
- How quickly might the canopy widen in San Diego?
The trees are tall but currently fairly narrow ( a few feet). Roughly how many years might it take for a nursery-grown Little Gem of this size to develop a canopy around 6–8 feet wide in the San Diego area (in ground or otherwise)? My location is 9211, approximately 2 miles from the coast, and the proposed location receives direct sun basically all day as the sun crosses the sky.
How should I prep the "Clairemont clay" if I do plant them in the ground immediately? I know they need drainage so they don't rot in their own juices.
Most importantly, if this isn't the right option (even after all of the research and sunk cost), does someone have a better option that is plant-based? I am thinking maybe it is to plant them in the yard, but use a long planter next to the windows until the trees get big enough to do their job. Or, don't plant them in the yard at all and do something else.
Thanks in advance for any help.