Dry shade gardening is one of the big problems faced by many gardeners. In my normal fashion, here are two things you have to understand.
Surviving vs. Thriving
The first is that there are some plants that will “survive” in dry conditions. There are very few plants for perennial borders that will “thrive” in dry conditions.
So the first message for gardeners is that if you want a garden, then you’re going to have to apply enough water to keep your plants alive and thriving. You can plan for a xeriscape garden all you like but unless we’re talking about hardy succulents and cacti and other specialized Southern plants adapted to these conditions, then the plants will do better with the water they require.
If you’re gardening in places that have enough cold weather to kill these specialized Southern plants you’re looking at having to water if you want a thriving garden.
Let’s Define Shade
Here’s a rough diagram to get you thinking about how much shade you have in your garden.
How does this work?
Rules of Thumb. This is not carved in stone but is a general guideline for planting dry shade gardens.
The 10-2 section is full hot sunshine and counts 5 hours instead of 4 hours
- Full sun plants want 8 hours of full hot sunshine
- Part sun plants want 4-6 hours of sunshine
- Shade plants want 2-6 hours of sunshine
(Now, having said that, understand the huge difference in plants and gardens and regions. Please understand this is a general guideline and your soil and gardening style as well as the plants you select will determine your results)
- 6-8 hours of sunlight if it includes the 10am -2pm section is full
- 6 hours of sunlight if it includes the 10am-2pm section might be
considered full sun
- 10am-2pm in Southern gardens is full sun and often more than that
will burn plants
- 8 hours of sunlight if it doesn’t include the 10am-2pm section is
Dry Shade Gardening Under Trees
Let’s not pull any punches here either. There are several different kinds of trees that we find in our gardens. We have open-leaved trees such as birch or apple that allow a fair bit of light through their leaf canopy. So you can plant low-light plants such as Hosta (and anything that will survive where a Hosta will survive) under such trees and they’ll get enough light to live.
We have medium to heavy canopy trees such as maple that create two zones of shade. The first outer zone is where the low-light plants can get enough light. The inner zones are places where the light levels are simply too low.
We have dense canopy trees such as evergreen pine and spruce that do not allow very much light at all to penetrate below themselves and no garden plants will survive in those zones. Some plants will survive in the border zones
A Characteristic of Trees.
They’re bullies. They’re greedy. It’s a fact of biology that trees are the big bullies in the gardening world. They control the light because of their height and leaf canopy. They control the water because of their extensive root systems.
In the diagram below, you can see the dripline (the edge of the leaf canopy) has a distance from the trunk of X. The roots actually go out from the trunk a distance of 2X. So if the distance from the trunk to the dripline is 20 feet, the roots are 40-feet out from the trunk.
Bottom line. A tree controls what survives underneath it.
The Solution to Dry Shade Gardens
You have several. You can water plants under open leaf canopy trees to help keep them hydrated. Instead of providing the garden with one and a half inches of water a week, you kick that up to two and a half to three inches. Half for the garden plants and half for the tree. Both will thrive.
You can put plants on the border zones and get enough light levels to grow a garden (see above for watering)
You can’t really grow plants in the deep, dry shade areas under heavy and dense canopy trees so stop trying. Apply mulch in these areas to stop the odd weed that makes a valiant attempt at life under there.
The real bottom line is that it is virtually impossible to battle biology. If you have dense shade and extensive root competition, there’s no plant solution to this. You just can’t beat Mother Nature.
- You adapt by watering more and finding the light zones for part shade or shade plants.
- You hardscape/mulch the dense shade areas where nothing will grow.
- You accept that nature does indeed determine what kind of garden you can grow.