It is winter in California. The days are short, it’s wet, and the temperatures are relatively mild. What this means for the gardener is that it is a great time to start considering the adjustment of plants in your garden.
To a large degree, the evolution of a garden is the process of managing growth. The growth rate of a plant and its eventual garden size are among the most difficult factors to determine due to the many variables that affect a plants potential in a garden.
One must consider several factors. What root pruning has occurred in its cultivation or containerization? This will permanently affect the plants potential and rate of growth in the garden setting. The quality of the soil, its fertility and porosity and of course, the care of the plant over time will all impact its potential growth.
We seek instant gratification so we naturally over plant. There is nothing wrong with this as long as you anticipate thinning the plants in the future or you are willing to accept the natural dwarfing effect of root competition.
Close planting also tends to create a canopy of foliage that reduces water loss and inhibits weed growth. I tend to plant closely with low shrubs and ground covers but space my trees carefully to avoid dense shade.
I have planted trees knowing that some will need to be removed in the future. Naturally, this makes me indispensable over the long term! In the case of shorter lived perennials and shrubs, their required replanting in 4 – 5 years will allow for this.
Trees planted from small liners will consistently overtake container or B&B (balled and burlapped) trees. This would typically occur over a ten year period. Ultimately, the smaller initial plantings will be many times the size of the nursery grown plants. This is particularly noticeable with trees. The smaller the initial plant size, the more fragile the plant and the more susceptible to damage or poor horticulture in its early stages of growth. For most gardens, the inherent advantages of growth are offset by the need for immediate effect and the survivability of the larger root system.
The good news is that with most plants the slowing of growth will work to our advantage. We do not need the sixty foot tree. If its growth is affected as I have described above, its potential in our garden may be closer to thirty feet and in a time frame we will appreciate. I use many 2 – 4” caliper (trunk width) plants in my projects. Because of the root pruning inherent in the process, these trees will grow more slowly. If they are beautiful to begin with, this does not present a problem and is often an advantage.
How does this relate to plants grown in containers? These have also been root pruned by the nature of the potting process. There are two issues that one needs to be aware of with containerized material. The first is to get the plant from a reputable grower who has transplanted it at just the right time, avoiding circling or root bound root balls. The second issue is the type of soil in which the trees have grown. Japanese maples grown in very light soil mixes and fed constantly will have a whip-like growth that is not natural to the species. It takes a few years and good pruning to restore the natural character of the tree. When removing a plant from a pot, if there are significant roots on the perimeter it is important to cut those vertically to help generate new root growth outward from the plant. If this is not done growth can be stunted permanently.
When either field dug material or containerized plantings have been moved once, they are relatively easy to move again within a few years of their initial planting.
Until recently the average home ownership in the US was 5- 7 years. What does this mean for our recycled gardens? For existing gardens it means that we inherit the planting decisions of previous owners – good and bad. The “good” is the fact that the house and site spoke to you to begin with or you would not have bought the property. Better still, you could see the potential of the garden as yet unrealized.
The result of the quick turnover in stewardship (or lack thereof) is that we have to assess the strengths of a garden and build on them. Often this will mean strategic thinning or removal of plants as well as relocation.
If there is any theme that is consistent in my history of garden creation and renovation, it has been that I appreciate the ephemeral nature of the garden while understanding those elements which give lasting structure to the design. I am not a sentimentalist when it comes to the garden.
If a plant is stunted or failing you must ask yourself how long it will take the plant to recover. When you look at the plant, do you see a thing of beauty or is it a moment of guilt – a continuing indisputable mark of your failure as a gardener? I have many failures in my garden. The secret to no-guilt gardening is to remove the evidence and move on.
Late winter in California just before spring is the single best time of year to root prune and plant. In mid February the soils begin to warm and there is a definite feeling of momentum building in the garden. Any root damage at this time is quickly repaired as the plants burst forth with their spring flush of growth.
The size of the plant, amount of foliage, and root structure are the determining factors in assessing the size of root ball to cut. Plants which have fibrous root systems such as grasses or perennials will be fairly shallow. With many perennials this can be as little as six inches of depth.
One of the factors which make perennials such high maintenance plants is that their roots are so tightly packed that as the clump spreads, the roots in the middle of the plant are starved and tend to die out. Thus lifting, separating, and replanting are needed; typically on a 2 – 3 year cycle, depending upon the rate of growth and fertility of the soil.
This is particularly true of perennials which are fast spreaders. We use these in the garden with great care because of the havoc they can create if left unchecked. I plant many of these types of plants in containers with the bottoms removed. I am also careful to use a container that will give me 2 – 3 years of expansion before slowing down due to the constriction of the vessel.
Woody shrubs are rarely considered for relocation, but I have had great success over the years with moving shrubs as long as we do it just before the plants go into active growth. The character and structure of the soil has a lot to do with the potential for this relocation. Very stony or sandy soils tend to not hold a root ball. In effect this allows the root ball to collapse, almost always causing damage and negating the advantage of moving the plant.
If the soil will hold, then success will depend on the vitality of the plant to withstand root pruning and still have enough energy to respond to its new location.
Before moving a shrub you should remove a portion of its foliage by either thinning or reducing in scale. This will reduce water stress as the plant reestablishes its root system.
In the transplanting process it is very important to use a sharp shovel to cut the roots. If you pull sideways or lift with roots still attached, the root ball is likely to collapse. It is also critical to lift from below and not by the stem in order to evenly support the root ball in moving phase.
If you have not ascertained whether or not the new planting hole has good drainage, all will be for not and you will lose the plant. Mound the center of the hole somewhat so that the roots drape down slightly and be careful to moisten the soil that the root ball is being laid upon.
If you are using a drip system of xero flow type bubbler it is essential that the emitters or flow of water be on the root ball or it can bypass the plant and another effort will have been wasted.
Assessing whether or not to transplant a plant is always a process of asking yourself if the effort is worth the risk. When you realize that Camellia is getting too large for its location and that to buy a similar shrub might cost you $500 – $1000, it clears the mind wonderfully.
My discussion of the above has not been to denigrate the importance of good planting decisions or of design but rather to acknowledge a relationship with ones garden that is proactive and positive. Do not think of the winter as a time of quiet reflection and inaction but rather as the moment to leap into action in your garden.
Our mild winters give us the opportunity to be active gardeners on those days between seasonal rainfalls. The time in this climate to step back and contemplate the garden is in the heat of summer when many plants should be slowing growth.
Wishing you all a very Happy New Year and prosperous gardening.
Jonathan Plant
