What to plant under a conifer?

In the forest as well as in the garden, it is rare to be able to appreciate the spectacle of exuberant vegetation under a conifer. However, by using a few tricks and appropriate plants you can decorate its foot in the most beautiful way!

Problems to overcome

Under a conifer, several parameters come into play, reducing the chances of spontaneous plant growth.

First of all, the needles of conifers that have fallen to the ground produce toxins that allow them to avoid any competition at their feet by inhibiting the germination of other plant seeds. Nutrients and water are thus reserved for them.

Some conifers, such as umbrella pines for example, have superficial roots that draw nutrients, making the soil very poor on the surface, so plants that would have succeeded in germinating do not find enough food to grow properly.

The sometimes dense shade that conifers produce is not suitable for most plants. Let's add to that a significant lack of water because the rain has a hard time penetrating the branches of these evergreen trees for the most part.

Here is a very worrying picture completed by the acidification of the soil caused by the decomposition of the famous needles preventing the calcicolous plants from settling down durably.

Solutions for planting under a conifer

No need to panic! Once the causes are known, it is always possible to get around them!

• Never sow seeds under a conifer, as we have seen, they will have little chance of germinating. Prefer to install already well-developed seedlings in cups or pots.
• Rake out the needles and replace them with a thick mulch of well-ripened compost to gently fertilize the soil. Work it in with a claw, taking care not to damage the tree's roots.
• When you decide to install a plant under a conifer, create a pocket of potting soil and add a handful of ground horn and dried blood mixture, not forgetting the mycorrhizae that will help your plant build a stronger and more efficient root system by entering into symbiosis with them.
• Choose only shade loving plants and forget about those that need sun to bloom.
• Don't hesitate to install an automatic watering system under your conifers to compensate for the lack of water.

Which plants should be installed under a conifer?

If it's a large tree with a bald trunk, think of the lianas that will climb along it. Clematis is ideal and you will find many varieties. Some ramblers can also be placed at the foot of your conifer, so choose the variety according to your climate and prefer ADR-labeled roses that are much more resistant.

Think also of climbing honeysuckles or the splendid ivy in its variegated versions.

As for ground cover plants, opt for white or blue periwinkle, which are always delicate and form a beautiful carpet!

If you prefer flowering plants, try bergenia, this plant that is so easy to grow that it will cover itself with bouquets of pink flowers without any effort on your part. The same goes for perennial geraniums, very hardy and floriferous, which will grow without any problem under your conifers, as will St. John's wort, which will offer you its golden yellow flowers from June to September.

As for decorative foliage, choose the asarum, whose many cultivars offer silvery shades of the most beautiful effect or for one of the many varieties of Brunneras.

We don't think much about lungwort, these plants with trailing rhizomes, with foliage that is sometimes silver or mottled, and which has beautiful flowers from February to May. Here again, you will have a vast choice among cultivars with a palette ranging from white to red, passing through all shades of blue and purple.

Outdoor evergreen ferns are also a great way to decorate the base of your evergreens with their textured fronds.

Heather plants also thrive in the shade of conifers and in this acidic soil. Plant azaleas in groups, or clumps of rhododendrons and camellias. If you prefer the wild side of heathers, create beautiful carpets with these easy to live with plants.

For a blooming winter, think of the multiple cultivars of hellebores. This plant known as 'Christmas Rose' has beautiful white, green, yellow, pink, red, purple and even black flowers, sometimes variegated or spotted, single or very double. What a great way to start a collection!

If you like surprises, plant bulbs and forget about them! Their blooming will be a renewed wonder every year. Naples cyclamen, wood hyacinths, anemones, snowdrops, muscarias, puschkinias, daffodils, bear's garlic, summer peppermint, botanical tulips, lily of the valley... You'll find plenty to stagger the blooms! Bulbs can also naturalize and form beautiful carpets over time, so take advantage of it!

Frequently asked questions about cedar

Famous for its use in hedges and windbreaks, the cedar is a splendid evergreen tree that can also be installed as an isolated subject in a garden. Let's see how to grow it in the best conditions to avoid the diseases and parasites that sometimes attack it.

How to water the cedar ?

Watering should be regular and abundant for the first 3 years after planting to ensure a good recovery. However, the soil must not remain constantly wet! It is all a question of dosage.

Automatic drip watering at the foot of each tree is recommended for hedges throughout the summer.

In winter, water every 8 days if it does not rain.

Beware, in Mediterranean regions: the winter drought can cause water shock in the first few years after planting, so be careful!

How to plant a cedar ?

Never plant a cedar in a constantly wet soil, it will not resist for long. Clay soils that remain very wet induce the appearance of the dreaded Phytophthora and other cryptogamic diseases. A plantation on mound with addition of draining material could be considered in these conditions.

• Dig a hole twice the size of the root ball in all directions so that the cedar can develop its roots well.
• If the cedar is purchased 'bare root' in the fall, prune the roots before planting.
• If it is potted, soak the root ball in a basin of room temperature water to hydrate it, then carefully remove it before untangling the roots.
• Pour a good layer of draining material at the bottom of the hole (pozzolan, gravel, stones...) to ensure good drainage.
• Spread a mixture of garden soil, river sand and compost on top.
• Add mycorrhizae powder to ensure good vigor and better resistance to pests and diseases to your tree.
• Adjust the height of the soil at the bottom of the hole so that the collar is flush with the soil surface.
• Spread the roots at the bottom of the hole.
• Backfill, packing the soil as you go.
• Form a basin around the foot to retain water.
• Water abundantly to evacuate the air bubbles present in the soil.

How to prune cedar ?

Sharpen and disinfect the blades of the pruning tools with methylated spirits or a flame before pruning. Choose hand shears or thermal or electric hedge trimmers (depending on the size of the hedge and its location in the garden). The blades of these tools should be kept parallel to the hedge to ensure effective trimming.

Wear protective clothing before pruning.

Remember to water the hedge well the days before pruning.

Maintenance pruning of single trees:

• Cut the dead wood short in the fall with a saw.
• Prune damaged branches with secateurs.

Pruning cedars in hedges:

• Prune twice a year in spring and fall. For aesthetic reasons, it is possible to prune during the summer.
• Prune the hedge from the bottom to the top, keeping the base thicker than the top to allow light and rain to penetrate. This will keep the hedge healthier than if it were pruned vertically.
• Be careful never to prune wood that is more than 3 years old and do not cut the head of the cedar, it would have a lot of trouble to recover.
• Use a string to obtain a straight hedge.

Is cedar hardy?

The cedar is very hardy (up to -20°C, even -25°C for the Canada cedar).

Beware, however, of certain cultivars with ornamental foliage that begin to suffer at -15°C.

Is cedar sensitive to drought?

Once well established, i.e. when the root system is well formed (which takes about 3 years from planting), cedar is drought resistant.

Can we replant a cedar in the same location to replace a dead or diseased tree?

It all depends on the disease. If it is phytophthora, its oospores and chlamydospores are capable of remaining dormant in the soil for at least 3 years, so it is strongly discouraged to replant a cedar (or any other plant susceptible to this fungus) in the same location.

Why is my cedar turning brown?

The browning of the foliage is a sign that must be taken seriously by the gardener because it can come from several causes, more or less serious:

• Before mentioning the terrible diseases that plague cedars, let's think about the lack of water that can result in scorched and wilted foliage. Lack of water can exist even on watered plants, when they are watered too little. For example, when rain falls but is not abundant enough to penetrate the surface layers of the soil. A mistake that novice gardeners often make is not to water because it has rained. However, it is enough to scrape the surface of the soil to know if watering is necessary! If the soil is dry below the first centimeter, then watering is necessary. Lack of water in the first few years after planting weakens the tree and makes it more susceptible to diseases and pests.
• At the same time, think of amending the soil with compost and organic fertilizers if it is poor in order to avoid deficiencies which will also weaken the tree;
• Another cause, much more formidable: the phytophthora (Phytophthora cinnamomi), a fungus that spreads on the roots insidiously to quickly reach the whole plant. This cryptogamic disease is fatal and contagious. Remove and burn the affected plant and do not replace it with another cedar for 5 years;
• Didymascella thujina, another fungal pathogen, manifests itself as brown discoloration of a few areas spreading in one season to many branches causing leaf drop. Cut and burn the affected parts, water with horsetail manure and often apply treatments with Bordeaux mixture.
• These two diseases are very frequent in heavy and humid soil;
• Foliage that turns yellow and then reddens and dries out associated with blisters on the bark should make us think of cortical canker (Coryneum cardinale), another fungus that attacks cedars with wounds (insects, pruning...). If the disease is caught in time, cut and burn the affected parts, apply a healing mastic on the branches and then treat with Bordeaux mixture.

When to plant the cedar ?

It is best to plant cedar in autumn.

It can also be planted in spring.

When to prune cedar ?

• Maintenance pruning is done in early autumn on trees grown in isolation.
• Hedged cedars should be pruned twice a year: in spring (May/June) and from late August to September/October.

What is the right spacing to create a cedar hedge?

The cedar grows quickly, so don't worry if there are gaps between your trees when you plant them, they will fill in within two years.

By respecting a spacing of one meter between each tree, they will develop in an optimal way by limiting the colonization by the parasites.

Respect the regulation imposing to plant at 2m from the property line the trees that will reach more than two meters in height.

What is the Latin name for cedar?

Thuja is a vigorous, fast-growing conifer in the Cupressaceae family. The Thuja genus includes 6 species native to the temperate zones of North America and Asia (especially China and Korea), however, there are multiple varieties.

The habit of this tree is conical to pyramidal. It has an evergreen foliage generally green with imbricated and flattened scales. The foliage can be toxic by ingestion (vomiting, diarrhea and stomach ache), its contact can cause dermatitis in the most sensitive people.

The flowering occurs in April/May and can cause allergies. The cones are sometimes ovoid, spherical, scaly, sometimes even horned.

What are the species of cedar?

There are 6 species of cedars, some of which are commonly used to create hedges. Let's not forget the taller cedars, ideal for isolated plantings in the garden.

• Thuja occidentalis, is the species most present in our gardens. This tree is otherwise known as Canada cedar and can reach 20 m in height.
• The habit is conical and the bark fibrous reddish brown. There are more than 100 varieties of this species which is widely used to form tall, dense hedges. The varieties 'Yellow Ribbon', 'Lutea', 'George Peabody' and 'Golden globe' have golden foliage.
• Thuja orientalis, or Oriental cedar, has a more restricted development (8 to 12 m high) and a slow growth. Its habit is conical. The foliage is dark green tending towards bronze during winter. This species is well suited to the bottom of rock gardens and beds, or even in pots for dwarf varieties such as 'Aurea nana' with golden foliage, or 'Decussata' with silver foliage.
• Be careful, this cedar does not tolerate wind and needs extremely well drained soil.
• Thuja plicata, known as 'California red cedar', has a pyramidal habit that becomes conical and very ornamental when mature. It can reach a height of 50 m. It is ideal as an isolated tree in a lawn. The variety 'Atrovirens' is perfect for quick hedging. This cedar is drought tolerant.
• Thuja koraiensis, the Korean cedar does not exceed 10 m in height. It can be used as an ornamental in Japanese style gardens for its green foliage with silver reflections and its drooping habit.
• Thuja sutchuenensis is a rare and endangered species native to the Sichuan province in China. It was thought to be extinct until a few specimens were discovered in 1999. This tree can reach 15 m in height.
• Thuja standishii, the Japanese cedar, grows at high altitude (between 900 and 1800 m). It can reach a height of 35 m. It has a conical shape and dark green foliage with silver stripes on the back. It is cultivated as an isolated plant for its ornamental appeal.

What are the best growing conditions for cedar?

The cedar appreciates well-drained soil because it fears having its roots constantly soggy. A deep and fertile soil suits it very well as long as it remains light.

This tree appreciates a sunny exposure but also tolerates half-shade in the warmest regions.

What are the most common pests on cedar?

• Red spider mites can cause serious damage. The leaves turn yellow and then fall off, and tiny webs can be seen on their underside. To prevent them from taking hold, water the foliage every day.
• The bupreste, a beetle whose larvae are phytophagous can condemn the tree in a short time. Oval-shaped holes in the bark indicate its presence. To prevent them, water and spray the foliage with nettle manure.
• Scale insects can weaken cedars. Exochomus quadripustulatus or Rodolia cardinalis, two species of ladybugs, can be used for biological control.

Fir trees, spice trees, how to recognize them?

In the vast family of conifers, few people can tell the difference between a fir and spruce, especially since the famous Christmas tree has been confusing the issue for decades. Here are a few tips to avoid making mistakes and to recognize them.

What is a fir tree?

A real fir is a coniferous tree that belongs to the Abies genus, which includes about fifty species of trees with a high growth rate (up to 50 m high for Abies alba). Firs grow naturally in mountainous and northern regions. Very hardy, they appreciate rich, fresh and well-drained soils with an acidic tendency.

What is spruce?

The spruce is a conifer that belongs to the genus Picea, which includes about forty species of trees growing in the cooler areas of the Northern Hemisphere. Very hardy, they like full sun and acidic, cool and well-drained soils.

How to differentiate a fir from spruce?

To differentiate the two types, there are a few tricks:

1- the needles 

• Fir branches have linear and flattened leaves (needles) that are often shiny green and have two white stripes on the back along the length of each leaf. When pulled off, they leave a round scar on the branch.
• The leaves of the spruce are arranged all around the twig. They are tough and have 3 sides that can be felt when a needle is rolled under the finger. The tip of the needle is prickly. When a leaf is torn off, a deep scar is left on the branch taking a small piece of bark.

2- Cones

• The female cones of the fir are born around May-June at the end of the branches, they are compact and purple-blue in color, at maturity they split and release the seeds. At the top, the male cones, often green and then purple blue to brown, appear later in the season. The female cone is erect and remains on the tree, where over time, only its central part called candle will remain.
• The female cones of the spruce carried by the main and secondary shoots are woody, oblong to cylindrical and especially pendulous, which definitely differentiates them from those of the fir, which are well erect. They fall to the ground in autumn. The yellow or red male cones, ovoid, appear in March

The myth of the Christmas tree

For a long time, Picea abies, the common spruce, has been used for the Christmas tree market because it is one of the easiest to produce and one of the cheapest on the market. The term 'Fir' is therefore misplaced, as it is in fact a spruce. Nowadays, French producers offer for sale Abies nobilis or Abies nordmanniana, real fir trees whose needles are more resistant to the dryness of overheated houses in winter but which remain more expensive to buy.

Pruning and maintenance of the Florence cypress

Very graphic, slender towards the sky, the Florence cypress is an exceptional ornamental subject in a garden. From routine maintenance to pruning, here's how to maintain its distinctive habit.

The needs of the Florence Cypress

Cupressus sempervirens is a coniferous tree with a naturally conical habit, very resistant to the elements but also to pollution and disease.

It works wonders as an isolated subject to mark the entrance of a property or planted every 5 m to emphasize a wide path. It can also be planted in dense hedges as a windbreak or privacy screen thanks to its dark green evergreen foliage.

Easy to maintain, it only requires a very sunny location and extremely well drained soil to grow.

After planting, remember to water it regularly for the first two years to give it every chance of recovery. In this respect, it is always preferable to plant a young bare-root plant in autumn rather than an older plant in a container. The former will have a better chance of recovering, will be more vigorous and will quickly catch up with the latter.

Once well established, the Florence Cypress will be satisfied with what nature offers in terms of watering.

If you wish to see it grow faster, as part of the installation of a hedge for example, do not hesitate to scratch a little compost and ground horn powder at its foot in spring and then every two months until autumn. This large tree can grow up to 30 meters high if the conditions are right.

Pruning the Florence Cypress

A Florence Cypress can grow very well without any pruning being done on its branches; it will then keep its natural habit but will become very tall.

It will keep its natural growth habit but will become very tall. However, some pruning can ensure a better branching and thus make it denser and more bushy.

When to prune the Florence Cypress?

Prune in spring and a second time at the end of August if necessary.

How to prune the Florence Cypress?

• You should only prune the young stems and never attack the old wood.
• Proceed in spring on the young shoots when they reach 10 cm. Prune them by half so that the branches branch out to make the subject more bushy when it is young.
• On older plants or for hedges, prune in the spring the shoots that protrude all around the plant in order to regain aestheticism. If you need to contain the plant in height, prune gently, very regularly, without ever cutting into the old wood.
• A second pruning can be done at the end of August to keep all its splendor to your hedge. This pruning simply consists of removing half of the ends of the shoots that have developed during the summer.

Trimming a coniferous hedge

Vigorous conifers used to form hedges need pruning to keep an aesthetic appearance throughout the year. Let's see how to proceed...

When to prune your coniferous hedge?

Leyland cypress or cedar are the two species most often used to create hedges. These trees are fast growing and have an amazing development if the growing conditions are right for them. Keep in mind that in the wild, these trees can grow up to 20 meters tall, so you need to curb their eagerness to grow twice a year. The first pruning is done in April or early May, the second at the end of August if necessary.

General information on pruning

Conifers sometimes have a tendency to recede from the base, regular pruning should avoid this phenomenon.

To trim your hedge, use a lopper, shears or a hedge trimmer.

If you are pruning high up in the tree, you may want to use a scaffold to avoid having to keep moving your ladder and wasting time securing it to the ground.

If you use the hedge trimmer, keep it level with your body to gain precision and limit fatigue (and tendonitis).

Put a line between two stakes to determine the height of your hedge, so it will be straight and not form 'waves'.

Always trim your hedge so that its base is wider than its top. This allows for better air, light and rain penetration and compensates for the ever-increasing top growth.

If it snows at your place, do not prune your hedge flat during the second pruning in August but make a rounding at the top so that the snow does not break the branches.

How to prune a conifer hedge?

Start by placing the line horizontally to determine the maximum height of your hedge.

First, trim the base of your hedge. To do this, remove the young shoots by cutting off 2/3 of the end of the stem with disinfected shears. The width chosen will then be the maximum width of the hedge.

Never prune in the old wood because new shoots could not form. Moreover, pruning large branches is an open door to various cryptogamic diseases. If you ever have to cut this type of branch anyway, coat the wound with clay to protect it.

Keep the blades of the shears or hedge trimmer parallel to the hedge.

Then step back and examine your work to determine any oversights.

Once the bottom is trimmed, set up your scaffold parallel to the hedge. Be sure to calculate its height so that you don't have to bend or kneel to trim your hedge. The tool you use must be able to stay in the extension of your arm when standing.

Trim the sides and then the top, following the line. Step down from your scaffolding to take a step back and identify any adjustments that need to be made.

Choosing the right hedge plants

Growing conditions

The first thing to know about a plant, when you want to buy it, is the way it has been cultivated?

Cold resistance 

Has the plant been grown in a heated greenhouse, cold greenhouse or outdoors? A plant grown in a greenhouse, where temperatures do not go below 0°C for a cold greenhouse, does not have the same capacity to resist the cold as a plant grown outside. The first climatic hazard will be fatal.

Disease resistance 

Has the plant received phytosanitary treatments or not? If, during its first months or years of cultivation, it has received treatments, its capacity to defend itself against external aggressions is null; it will thus remain dependent on its treatments, to face possible future diseases.

The capacity to feed itself 

Has the plant received regular fertilization or not? A plant that has grown with a lot of fertilizer has not developed an efficient root system. If, once planted, you stop giving it nutrients, its recovery may be compromised.

A plant from an organic nursery that uses natural treatments in a reasonable way is prepared to grow and prosper later on with a minimum of care.

Points to check

At a glance you can also verify, in part, the quality of a plant for sale.

The root system

A plant that is not sufficiently rooted has little chance of recovering after being transplanted.

If when you gently pull the plant by the stem to remove the root ball from the pot and some soil remains stuck on the edges of the pot, the rooting is bad.

On the other hand, too strong a rooting, visible by roots that turn at the bottom of the pot, can cause the formation of a root bun, which will eventually suffocate the plant.

Tip: good rooting can be seen when the root ball is firm and keeps the shape of the pot when unstuck.

Branching

Numerous branches are a sign that the plant has been pruned several times, by a professional, to give it a bushy and dense habit, ideal for a hedge.

The root ball

The trunk, just below the collar, must be attached to the root ball. If it is not the case, do not buy it.