Growing and Caring for Conifers
Conifers are woody plants, which means that they have stems and trunks of wood, which are covered with bark. They have woody stems even if they are ground covers or tiny miniatures that grow a fraction of an inch a year. Most of us think of trees when we hear ‘woody plants’ but there are thousands of shrubs, groundcovers and vines that are included in the category. Growing and caring for conifers and other woody plants is generally the same.
Woody plants need water, nutrients and sunlight, just as herbaceous plants do (herbaceous refers to soft, green stems). However, they have particular requirements regarding soil type and root treatment, as well as sometimes needing staking. Pruning is also more complex than with herbaceous plants and is done for both structural and aesthetic reasons.
Growing and Caring for Conifers: Selecting
When you are shopping for conifers, and this holds true for woody plants in general, you need to pay attention to structure, roots and overall health. Woody plants grow more slowly than perennials and it is important to evaluate them using ‘tree time’, understanding that problems are slow to develop but also slow to correct. When you evaluate a conifer for purchase, take note of the following:
- Is the color true to its intended description? For example, a golden conifer that’s supposed to be deep green indicates a lack of nutrients.
- Is it structurally sound, e.g. if it is a plant that is supposed to have a excurrent, ‘Christmas tree’ shape, does it? Is there evidence of awkward branching? Will it stand without staking?
- Do you see girdling roots at the crown? This could create problems going forward.
- How deeply buried is the root flare? It’s critical for a conifer’s root flare (the point at which the roots begin to “flare out” from the trunk) to be visible at the soil surface. Many woody plants are buried far too deeply. The plant must be ‘excavated’ so that the flare is visible. You may remove any small, adventitious roots that have filled the soil above the flare. This is one of the biggest problems with nursery stock.
- If possible, pop the plant out of its pot. Is it excessively root-bound? How much ‘root management’ will be necessary? With rootbound plants it is important to tease apart (sometimes cut apart) the roots.
Woody plants are grown in one of two ways: in containers or the field. Container-grown plants are much more likely to be root-bound than those that are field grown, however their entire ‘history’ is evident in the container, and it is relatively easy to get a look at the roots. They are grown in a potting medium that is generally very fast draining, but should be removed as much as possible before planting. Field grown plants are exactly that: they are grown in fields in the grower’s native soil, then root-pruned, excavated and the root ball wrapped and tied in burlap, and often referred to as balled-and-burlapped (B&B).
B&B conifers have an unique set of issues:
- The soil is often clay, and the clay ball often buries the root flare.
- There is often much more root trauma involved with digging and preparing these trees, which means more transplant shock and a greater need for supplemental irrigation.
Growing and Caring for Conifers: Placing
- It is always helpful to know the climate where your conifer is native. Consider the amount of heat, sun, wind, drainage and rain that a plant receives in its native habitat, and try to replicate this as best you are able. Some conifers that are native to very difficult environments are adaptable to easier conditions, such as mugo pines. Others are much fussier. You will learn from other conifer collectors, or, even better, from experience!
- Conifers with blue, silver, or dark-green foliage look and perform their best when planted in full sun.
- Most golden conifers look and perform best when they receive morning sun and some afternoon shade. Some of the golden cultivars will burn in full sun until established, which can take 2-3 summers. A few never burn in full sun. Check the plant description to be sure, or better yet, consult with other conifer lovers in your area.
- Conifers with white variegation tolerate very little to any direct sun. However, in deep shade, the variegation will often be suppressed. Bright light but never direct sun is the “sweet spot” here.
- Some species naturally grow in the understory of large canopy trees. These do quite well in places of low light. Chamaecyparis, Taxus and Tsuga are the best conifer species for shady locations.
- Remember to consider growth rate when placing your conifer; fast growing selections will need space to expand.
Growing and Caring for Conifers: Preparing for Planting
- Dig a hole no more than the depth of the pot / root ball and twice as wide. If your soil is poorly-draining, consider planting your conifer in a slightly raised position, and mounding better-draining soil around it. DO NOT amend the planting hole itself; you will be creating a ‘bathtub’ that will fill with water.
- Do not add organic amendments of any kind to the soil. In nature, woody plants live in un-amended soil. You can use pebbles or other inorganic materials to increase drainage in the mound, if necessary.
- Remove any excess soil above the root flare, then loosen the roots, especially roots that wind around the inside of the pot and especially girdling roots near the trunk. If you cannot untwist the girdling root(s), cut it off at the origin.
- Spread the roots outward into the hold in a radiating manner.
- Back-fill, ensuring that the root crown is visible.
- Stake if necessary, taking care to remove any stakes that were used in the pot, and inserting a new stake or stakes at the outer edge of the rootball and tying loosely.
- Fertilizers and transplant tonics are not necessary and can do more harm that good. They promote excessive top growth before roots develop.
- Mulch around the root ball, taking care to keep mulch away from the trunk. Mulch will help keep roots cool in summer, warm in winter, and help retain water and retard weed growth.
Growing and Caring for Conifers: Watering and Staking
- Thoroughly water your new conifer upon planting. This ensures proper contact between roots and soil.
- For the first few years in the ground, water when the soil is dry to the touch 1 to 2 inches below the surface.
- After 3 to 5 years, little to any supplemental water is necessary provided you live in a climate that receives natural rain during the growing season. If you live in a summer-dry climate, additional irrigation is generally necessary.
- Once planted, a stake may be necessary if the plant is tall, wobbly in the hole and you live in a windy area.
- A stake should be in place for only as much time as is necessary to allow sufficient development of the root system to hold the plant upright. Trees, particularly, need to flex and move in order to develop trunk strength, and long-term, tightly bound staking prevents this from happening.
As noted, conifers rarely need fertilizing and do not need or benefit from additions of organic matter. Do not overwater, and check and adjust/remove any staking in the first year or two. Diseases and pests are generally genus and location-specific; some genera have very few problems, others, such as hemlocks (Tsuga) are rapidly being diminished by a specific pest, this case the wooly adelgid. Refer to information about your specific plant and learn about pests and diseases prevalent in your area.
We will discuss pruning in a separate entry.
Enjoy your conifers and don't hesitate to call on ACS members for suggestions or feedback!