What to plant in retaining wall planter box


If you could please suggest some plant ideas for this planter box…I would like height (to hide wall behind) and perhaps some colour. The box is 3 ft x 5 ft
At first I thought 3 Degroot cedars…then I thought some yews. … I have 8 annabelle Hydrangeas Along the other side (not shown in photo) …..please help! I would like to plant now if possible. I know it is late in the year. The plants would receive Mostly full sun


Thank you for contacting Toronto Master Gardeners regarding plant recommendations for your new planter box.

From the photo, it appears that the planter box is beside a hot tub or swimming pool. There are several things to think about when planting in such a location. This article covers them in some detail: https://www.poolsuppliescanada.ca/landscaping-tips-for-your-new-inground-pool.html .

Briefly, you want to avoid plants that shed a lot of plant material (leaves, flowers, berries, pollen) into the pool as this could affect the pool’s chemistry, and cause an algal bloom. Also, avoid plants that have thorns or prickles e.g. juniper. Look for plants with a shallow root system that are not water seeking so your pool’s structural integrity will not be compromised. Ideally, the plants should be at least 3 feet from the pool edge.

Evergreens such as boxwood, cedar and yews would provide year round privacy. Before you buy, check the ultimate height and width of any evergreen you plan to purchase. Three De Groot spire cedars would be a good choice. This tree is a slow grower that can reach 9 feet tall and 2 feet wide. It has low tolerance for dry or drought conditions, so the soil should not be allowed to dry out. With a typical clearance of 1 foot from the ground, there should be room in the box to add some colourful annuals around the cedars.

You might consider a lower growing shrub, Emerald Gaiety Wintercreeper which has attractive white-variegated evergreen leaves. It does produce small pink fruit with orange seeds. It is very adaptable to both dry and moist locations. It grows to 5 feet tall and spreads as far as 9 feet, but can be easily pruned to maintain the size you want. Colorful annuals could be planted to fill in the planter until the plant gets established.

Another possibility is an ornamental grass. Although not evergreen, many grasses look good in winter. Here are a few examples of grasses you could plant:

  • Feather Reed Grass (Calamagrostis x acutiflora ‘Karl Foerster’), which can grow to 6 feet tall, and 2-3 feet wide. It doesn’t shed seeds or spread. It prefers medium to wet soils. Here is some information on this grass.


  • Panic/Switch Grass(Panicum virgatum), which can grow to a height of 4-5 feet. Cultivars in various colours are availableg. Prairie Fire Red Switch Grass, Heavy Metal Blue Switch Grass. It prefers medium to wet soils. Here is some information on the standard cultivar of this grass.


Your planter box appears to be situated on a concrete slab. It the box does not have drainage holes, you must make some as plants left in standing water do not thrive.

The best time for planting coniferous trees is from mid- to late-spring when the soil has warmed up a little. The second best time is the fall, as long as the soil is workable. Euonymus and grasses can be planted now.

If you want to plant now, visit a reputable garden center and see what is available that would meet your requirements. Whatever plants you choose, do fill your planter with top quality potting soil and mulch the plants well. Protect newly planted shrubs from drying, winter winds with burlap or other tree wrap. Water the plants regularly after planting until the ground freezes.

Good luck with your planting project.