(News article for February 15, 2025)

Much landscape planting is done in the spring. This is a good time to plant warm season annuals and root-hardy tropical perennials. Early spring is also an acceptable time to plant trees, shrubs, and temperate zone perennials, though fall is often considered preferable.

Good bed preparation is important, especially when planting trees, shrubs, and herbaceous perennials that we want to live for many years.

Remember to call 811 (Louisiana One Call) to mark utility lines before you dig or till, to avoid unpleasant surprises. If there are trees or shrubs near where you plan to put the bed, consider how their roots may be disturbed. We estimate that a tree’s roots extend to roughly twice the width of its canopy, or three times the width for trees with upright (columnar) forms. You may want to move the bed or change its size or shape to minimize disturbance of valued trees.

You can take a soil test to determine if soil pH needs to be adjusted and if nutrients such as phosphorus, potassium, calcium, magnesium, or sulfur need to be added. Nitrogen can be applied after planting, but it is more efficient to mix lime (if needed to raise soil pH), sulfur (if needed to lower pH), and some nutrients into the soil while you have the chance.

Before tilling, it’s helpful to kill any turfgrass or perennial weeds, since they can regrow from roots or other underground structures. A non-selective, systemic herbicide, such as an appropriately labeled glyphosate product, is one of the most effective ways to do this. Make sure the product you use does not have restrictions that limit your ability to plant back on that site. If you use glyphosate, try to wait at least three weeks after you apply it before tilling. This gives it time to move into the roots and kill them. Follow label directions when using any herbicide.

Another way to kill weeds before planting is to keep light from getting to them for an extended period. People sometimes use cardboard or newspaper to do this. Heavier, reusable materials can also be employed. Unless the material is left in place for a very long time, the effect will likely be comparable to using a burndown (non-systemic) herbicide: The tops of turfgrass and weeds will be killed, but perennials may regrow from roots or other structures. Likewise, if you just till the area without killing turfgrass or weeds, some will likely return.

Till the ground to approximately 6 to 8 inches deep. It’s generally helpful to incorporate about 2 inches of organic matter, such as compost or aged pine bark. If the bed is in a low-lying spot, you may want to incorporate a combination of organic material and sand to improve drainage. Keep in mind that the mixture will settle over time, so the height it’s at when you prepare the bed will be reduced. Along with these, till in any needed lime and nutrients.

When planting within the bed, use good planting practices, including making sure the soil underneath plants is firm. This is important so that, e.g., trees do not sink to the point that their trunk flare is below the surface of the soil.

Remember to follow the right plant, right place principle and to group plants according to their needs for water, sun and shade, soil pH, etc.

After planting, it’s helpful to spread mulch over the surface of the bed to suppress weed growth and moderate temperature and moisture levels in the soil. Try to keep mulch several inches away from the bases of tree trunks and shrub stems and at least 6 to 12 inches away from house foundations.

Let me know if you have questions.

Contact Mary Helen Ferguson.

(Photo by M.H. Ferguson)