Have you ever wondered why some recently planted, healthy-in-the-pot plants die before becoming established in your gardens?
You’d be surprised at how many of our nursery’s customers raise their eyebrows at our explanation for most premature plant deaths – improper planting! They are even more astonished when we suggest soiless growing mediums are a leading contributor to the death. These two possible causes are linked and this article draws the connection.
Underground Air Barriers
First, let me present an invisible physical phenomenon that naturally exists at the junction of two soil types. A microscopic layer of air is often found where two distinctly different soil types meet. This air layer is more evident after adjacent and distinctly different soil types have been dried out and then re-wetted. If one medium is selectively and incompletely re-hydrated, the layer of air acts as a barrier to conduction of moisture between the two soil types. This’ air barrier’ naturally stops the capillary, or wicking, transfer of water molecules to adjacent soil particles.
Now consider that your ready-for-planting plant is likely growing in a medium rich in peat or bark and your garden soil composition can range from sticky clay to beach sand. The two distinctly different soil type juxtaposition, with associated ‘air barrier’ creation possibilities, is about to be created!
Moisture Differences Matter
Second, consider what happens when a delicate root is exposed to air. If there is enough time for the response, the root will innately turn away from unfavourable conditions (e.g. an air layer) and seek out more favourable environments. If response time is inadequate, root tips simply dry out. This happens all the time in pots in the nursery. Roots do not grow beyond the pot walls even if they are fibre pots that allow roots to penetrate their walls upon appropriate planting. The roots turn inward and continue growing in a circular pattern within the more favourable soil conditions in their pot. In the transplanting situation, the existing potted root mass may be the most favourable environment if it continues to be pampered by the gardener through selective watering. It is so easy to unwittingly encourage roots to stay within the confines of its former home rather than encourage them to venture out into their new, more uncertain, garden soil home.
Lets return for a minute to moisture phenomenons common to soiless mixes. Even if covered with a layer of soil or mulch, they dry out faster than most garden soils. This is accentuated during periods of intense sunshine or moisture-sucking winds. At the other extreme, soiless mixes also absorb and hold more moisture than many garden soils. In the home garden this over-moist condition is often of our own creation - water conservation objectives lead us to selectively water new transplants and to not water the surrounding soil!
Our Recommendations:
With the preceding explanations of what can happen in soil environments, what do we recommend?
Dig a Wide Hole
First, roots need more than a ‘just big enough’ hole be prepared to accommodate their developing root system. This is especially true in clay or rocky soils and for trees and shrubs. Developing plants need room to grow extensive lateral roots systems which provide nutrients and moisture for growth. We suggest plants need three times the diameter of the purchased pot for successful establishment. Planting holes need be just deep enough to accommodate the root mass.
No Gravel Please
Gravel should not, under any circumstances, be placed as a discreet layer in the bottoms of beds or individual holes to improve drainage. Remember the air barrier phenomenon just presented. Gravel separating soil types magnifies the phenomenon. As well, in rainy weather, a gravel layer on top of a clay soil creates a bowl for water to pond in and prevent healthy root growth.
Prepare Premium Top Soil
When you build each garden bed, use the best grade garden top soil available. The addition of aged compost, when building the bed, will increase moisture retention, increase organic nutrient supply, and increase aeration levels for long-term healthy root growth. Aim for a compost to soil ratio of 1:3 (i.e. 25%). We use sea shell compost as we’ve had horrid expereince with salt-laced mushroom compost killing plants.
Build a Raised Bed
In clay soil areas especially, we suggest that gardens be constructed as raised beds to provide for adequate spring and post-rain drainage. Beds need only be raise 3-4 inches but up to 12 inches for wide beds is achievable. They do not need to be contained – just slope the sides.
Drainage Holes Anyone?
Before placement of top soil on clay areas, it is a good idea to to open up drainage channels for improved drainage. Plunging a garden or 3-tined hay fork into the clay, under the new bed loation, will assist water percolate into the soil.
Dozens of tine holes per square meter is not too much!
Time for the Rototiller
Use a rototiller to blend the first 2 inches of top soil in with the existing soils. This helps overcome potential air barrier phenomenon problems from arising. Following this blending, the balance of top soil can be placed on the garden. In sandy and rocky areas, imported quality garden soil can be simply mixed in with existing soil to better the overall soil quality. The deeper the prepared bed the better – 24” is not too much.
Water, Water Everywhere
At planting time thoroughly soak planting holes and the soil around the planting area. The plant to be planted should be soaked to the same degree as the receiving soil to give uniformly moist conditions to roots and the soil. If the root mass is at all dry, immerse the root mass in a bucket of warm water to achieve complete hydration of peat and bark particles.
Feed the Roots Please
Place a non-burning, root-stimulating fertilizer, such as powdered bonemeal, in the bottom of each planting hole after the soil soaking procedure. Place a thin layer of soil over the bonemeal to separate tender root hairs from the bone meal. The roots will grow into the bone meal reserve to get the root-strengthening nutrition. We caution against using water-soluble fertilizers, such as those with a 10:52:10 formulation, in the soil-soaking or watering-in stages. These fertilizer salts can damage root hair growth. In addition, the elevated phosphorus level (middle number) reduces development of beneficial soil-borne fungi which colonize developing roots to make them stronger and more drought resistant. (See ‘Plants Crave Fungi’ in Spring 2004 Epic Gardener for details on this topic)
Doctor the Roots
At the moment of planting, each plant should be inspected for the need to ‘doctor’ its root mass. Lightly root-bound plants need circling roots to be gently teased or washed apart to break away from their circling pattern - a pattern they’d continue after planting. If the roots are tightly bound around the periphery of the root mass, make about four - ¼ inch deep incisions, using a sharp knife or box cutter, into the root mass to stimulate new growth outward into surrounding soil. If few roots protrude from the potting medium, about 1/3 the medium should be teased or washed off the root ball to expose the roots to their new garden soil. In all cases, the objective is to assist roots make immediate contact with their new growing medium and negate any limiting ‘air barrier’ condition from arising. Do one plant at a time! Don’t leave delicate roots exposed to the air, where tender root hairs can dessicate and quickly die, for more than a minute – even that can often be too long. If you are delayed in planting for any reason, cover unpotted plants with a wet towel or place then in bucket of water to keep the roots from drying out.
No Stomping Please: Settle for Water
At the soil backfilling stage, loosely place soil around the prepared-for-planting root mass. In addition, we recommend a fungal supplement be added to the backfilling soil to help roots get established. Some nurseries (ours included) are pioneering a 5-year warrantee on trees and shrubs which use the appropriate fungal supplement at planting time (see our web site www.rcgardens.ca for details). Resist the temptation to punch, pound or stomp the soil. Compacting the soil around the root mass reduces needed air spaces for optimum root and fungal developmenet. To settle the soil around the root mass, gently provide copious amounts of water to eliminate large air pockets and bring roots into direct contact with soil particles. Aim to establish a slight depression in the soil, or create a 2-3 inch raised ring of soil, around fresh transplants to catch available water (rainfall or applied) and direct it to the developing root system. To reduce evaporation loss due to wind and sun exposure, apply 2-3 inches of bark or other decorative mulch around the planting area.
No Fertilizer for a Week
Do not apply water-soluble fertilizers around the planting area at planting time. Wait about a week, allowing roots to become established in and accustomed to their new envronment, before adding any addtional fertilizers. When choosing fertilizers, organic fertilizers are much better because they favour the development of the miriad of soil-borne organisms that support healthy root growth.
Other Steps to Success
The above planting tips will give plants the best chance to become successfully established and be better able to withstand slight stresses.
Are there other chores conducive to succcessful plant establishment?
Keep them Moist
For the first year assure that a uniformly moist soil is maintained, at all times, around establishing plants. Your local environmental and soil conditions dictate the frequency of adding supplemental water. Ideally the top 2-3 inches of soil should become dry-looking (not parched) before irrigating again. This encourages the ‘breathing’ of the soil – it allows air to be sucked ionto the soil to refresh needed oxygen for optimum root metabolism. With the use of moisture-retentive mulches you may have to peel back the mulch periodically to monitor moisture conditions. Inexpensive moisture probes, available at most garden centres, are a handy indicator tool that can assist in determining the proper timing of adding water to the soil.
Support Matters
Trees and shrubs likely to sway in windy periods should be provided with supports to keep them stationary during their root establishment stage. Root mass movement, occuring during windy periods, ruptures delicate roots trying to get established in the soil. Typically three guy wires (or ropes) per tree, with protective rubber hosing secured, but loose-fitting, around the trunk, are installed and brought to the ‘just tight’ stage. Attach the wires or ropes to posts or anchors, arranged in a triangle, making sure that they do not damage the tree’s bark.
Removal of the support ropes or cables should be done as soon as the tree is well rooted – usually in the second season. Stronger trunks develop in trees allowed to sway with the breezes, but firm root establishment is the priority concern.
Pamper Them for Winter
As the first winter approaches, ensure plants (especially late-planted ones and those in exposed locations) have thoroughly moistened soil so that your plants’ late fall and winter moisture needs are met. Even though the trees plants have lost their leaves or perennials’ leaves have died from frost, the roots will keep growing right up to complete ground freeze-up. A winter soil mulch (such as evergreen boughs or straw) should be applied, to within six inches of tree/shrub trunks, to moderate soil freeze-thaw conditions. Overwintering mulch should be kept about six inches away from tree trunks to minimize bark-gnawing rodents from nesting and feeding on your plants.
A protective blanket for trees and shrubs likely to be exposed to direct afternoon winter sun is good protection. Construct a simple frame, as high as the tree or shrub is tall, around small trees and shrubs. Simply pound four wooden stakes (2” X 2” wood is adequate) around the shrub or tree before freeze-up. At freeeze-up secure sheets of burlap, or other fabric, to the posts making sure the material does not touch the trunk or branches. The aim is to stop winter sunlight from ‘burning’ the foliage and bark - not provide insulation or complete wind protection to the tree or shrub.
Is there a Guarantee?
I hope with this information each of your plants survive and reach maturity. Unfortunately, in the horticultural world, it is impossible to guarantee every plant will survive and perform as stated in promotional literature - even if there is a written guarantee offered by the vendor. Knowledgable gardeners know that gardening success equates to putting the right plant in the right place and that requires an understanding of purchased plants’ soil, moisture and light requirements and then carrying out proper planting and after-planting care until the roots are established.
No one said gardening was goof-proof or a ‘no sweat’ activity.
