establishing landscaping in construction soil - Ask Extension
Despite adding organinc material during the planting of a new landscape on a new home construction site (top soil scraped off, heavy machines for mont...
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establishing landscaping in construction soil #877933
Asked July 19, 2024, 2:24 PM EDT
Despite adding organinc material during the planting of a new landscape on a new home construction site (top soil scraped off, heavy machines for months and lots of grading) the new plants look the opposite of robust. They are slow growing, often more yellow than green and are clearly not thriving.
I'd like to add 2-3" of Leaf Gro to the entire new planting beds (after removing the mulch) with a gentle raking betweein the plants. This is more than the 1" per year that is recommended in the poor soil article. Most of the existing plants are native with a wide diversity of species.
Are there any negative consequences to adding the 2-3" this year? Any other suggestions?
Montgomery County Maryland
Expert Response
Adding more than an inch of soil (compost included) atop existing plantings risks smothering too many roots (depriving them of enough oxygen) and causing worse plant stress or even dieback. Gradual addition of organic matter (OM) through yearly inch-deep compost applications, and/or replenishing a biodegradable mulch (bark, wood chips, pine needles, leaf litter, etc.) as needed are both great ways to gently improve the OM content of the soil in the root zone, as soil life "rototills" it in gradually.
In the interim, though, there could be many reasons for poor plant performance, not all of which may be due to soil conditions. Can you share photos of some of the symptoms? (You can reply more than once if you need to send more than the platform limit of 3 attachments per reply.)
Have you had a laboratory soil test performed? It would supply information about basic nutrient levels, acidity (pH), and OM content. This should be done before any more OM is added, to make the lab measurements more accurate. We can help to interpret the test results if desired.
Plants that are still establishing (in the ground less than 2-3 years) need regular monitoring for watering needs, especially in this ongoing drought. This includes species which are tolerant of drought once they are established. How long have the plants that are struggling been in the ground, and are they checked at least once weekly for irrigation needs? Soil moisture isn't just important to prevent overt symptoms like wilting and dieback, but it influences how easily plants absorb the nutrients they need (as they are taken up dissolved in water) and if moisture stress predisposes them to certain opportunistic fungal infections. Leaf yellowing can occur due to nutrient deficiency in the soil, soil pH that is too high or low for the species in question, drought, over-watering, and certain pest and disease issues. We can probably narrow that down with photos of the symptoms. By itself, the addition of OM to soils doesn't provide tons of nutrients (especially those readily-available to roots), but it can help poor soils retain nutrients, plus improve drainage and aeration for roots.
Miri
In the interim, though, there could be many reasons for poor plant performance, not all of which may be due to soil conditions. Can you share photos of some of the symptoms? (You can reply more than once if you need to send more than the platform limit of 3 attachments per reply.)
Have you had a laboratory soil test performed? It would supply information about basic nutrient levels, acidity (pH), and OM content. This should be done before any more OM is added, to make the lab measurements more accurate. We can help to interpret the test results if desired.
Plants that are still establishing (in the ground less than 2-3 years) need regular monitoring for watering needs, especially in this ongoing drought. This includes species which are tolerant of drought once they are established. How long have the plants that are struggling been in the ground, and are they checked at least once weekly for irrigation needs? Soil moisture isn't just important to prevent overt symptoms like wilting and dieback, but it influences how easily plants absorb the nutrients they need (as they are taken up dissolved in water) and if moisture stress predisposes them to certain opportunistic fungal infections. Leaf yellowing can occur due to nutrient deficiency in the soil, soil pH that is too high or low for the species in question, drought, over-watering, and certain pest and disease issues. We can probably narrow that down with photos of the symptoms. By itself, the addition of OM to soils doesn't provide tons of nutrients (especially those readily-available to roots), but it can help poor soils retain nutrients, plus improve drainage and aeration for roots.
Miri
Miri,
Thank you so much for your very thorough reply. I will plan to proceed with soil testing before adding the compost and reassess the irrigation system and how much water is being provided each week. I will send photos if any plants look particularly distressed.
Would you still advise 1/2 inch twice weekly with an automated irrigation system in place? I'm concerned that the gardens may be watered more often.
I appreciate you sharing your expertise.
Pam
Hello Pam,
General irrigation guidelines call for about an inch of "rain" per week, usually in one session (but spread over two waterings is okay) so it soaks in to a sufficient depth to reduce the risk of some of that water evaporating afterward and to make sure deeper roots are rehydrated. The linked watering page focuses on trees and shrubs, but can apply to perennials as well.
Miri
General irrigation guidelines call for about an inch of "rain" per week, usually in one session (but spread over two waterings is okay) so it soaks in to a sufficient depth to reduce the risk of some of that water evaporating afterward and to make sure deeper roots are rehydrated. The linked watering page focuses on trees and shrubs, but can apply to perennials as well.
Miri
