Alberta spruce: Picea glauca ‘Conica’ care & planting
The Alberta spruce is a popular Christmas tree. What is more, this slow-growing and compact conifer is great for smaller gardens and for growing in pots!
Alberta spruces (Picea glauca var. albertiana) are lush trees with dense, fine, green needles. This evergreen conifer is particularly suitable for small gardens, sunny patios and front gardens. Read on to learn how to grow Alberta spruce trees at home, including their preferred location and care requirements. As the Picea glauca ‘Conica’ makes an appearance in December in many living rooms, we will also cover whether it is poisonous.
Contents
Alberta spruce: origin and properties
The white spruce (Picea glauca) grows wildly in the forests of Canada, where it is even found in the Far North. It looks impressive with its harmonious shape and usually lives between 250 and 350 years. Based on this wild form, various densely growing forms were cultivated, which have become known as Alberta spruces because of their native home. Both the white spruce and the Alberta spruce belong to the pine family (Pinaceae). While the wild form reaches heights of up to 30m, the dwarf cultivated forms remain rather compact — depending on the variety, they grow between 1 and 4m tall.
The slow-growing Alberta spruces reach their final height after about 30 years. The square needles of the Alberta spruce are usually 1cm long and radially distributed on the branches. The young needles are light green, darkening to a blue-green as they age. As with all spruces, Alberta spruces are monoecious and produce male and female cones that hang downwards.
The prettiest varieties
There are various cultivated forms of the white spruce, all of which differ in size, growth habit and needle colour.
- Picea glauca var. albertiana ‘Conica‘: the Alberta spruce ‘Conica’ is a popular ornamental with its compact and strongly conical growth. Its needles are soft and shine in a bright green. It looks particularly good on its own. Picea glauca ‘Conica’ grows 3 to 4m tall and about 2m wide in the garden.
- Picea glauca var. albertiana ‘Laurin‘: this dwarf Alberta spruce tree only grows 0.8 to 1m tall and about 80cm wide. It is cone-shaped and has light green needles.
- Picea glauca ‘Zuckerhut‘: this white spruce ‘Zuckerhut’ is also a dwarf conifer. It grows 1.5m tall and 50 to 80cm wide. The soft needles grow densely, forming the classic cone shape.
- Picea glauca ‘Sanders Blue‘: another white spruce that has beautiful blue-green needles. It grows slowly in the classic cone shape with a pointy top. Like ‘Conica’, it grows up to 4m tall and 2m wide.
How to grow Alberta spruces
The optimal time to plant conifers like the Alberta spruce is September to October. The mild temperatures and the abundant rain in the autumn months help the tree to form new roots. A sunny to semi-shady location with well-drained but not too nutrient-rich soil is ideal. It is best to improve humus poor soils with some compost, such as our peat-free Plantura Organic All Purpose Compost. Our compost offers the best conditions for good growth, providing extra magnesium fertiliser to help the Alberta spruce to grow a dense green needle coat. Our compost is also airy and well-draining due to the wood fibres it contains, meaning the fine roots have an easier time spreading.
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How to plant an Alberta spruce in the garden:
- Loosen the soil with a digging fork
- Dig a planting hole that is twice as wide and deep as the root ball
- If the soil tends to compact, create a drainage layer of gravel
- Add up to 50% of compost to the planting hole, depending on the quality of the soil
- Water the root ball of the Alberta spruce before planting
- Remove the pot and scratch the surface of the roots with a knife or secateurs
- Place the Alberta spruce at the correct height in the planting hole
- Fill with a mixture of excavated earth and compost, pressing down firmly
- Spread a 5 – 15cm layer of mulch around the spruce
Growing Alberta spruces in pots
Picea glauca ‘Conica’ is ideal for growing in pots, but other smaller varieties can also be cultivated this way. In a sufficiently large pot that is at least 45cm wide, the shallow-rooted Alberta spruce will live happily on the balcony or terrace for several years. It is important that the drainage hole is as large as possible to prevent waterlogging. It is best to put a layer of horticultural grit in the bottom of the pot. A high-quality, slightly acidic and moderately nutrient-rich soil is suitable as a growing medium, such as our Plantura Organic All Purpose Compost. It consists of fine wood fibres and coir, making it more sustainable than peat-based composts, and it provides the Alberta spruce with the perfect balance of water storage capacity and permeability. Alternatively, if available, you can also use a sandy-humic garden soil.
An Alberta spruce in a pot needs fertilising twice between March and August. A granular fertiliser with a higher magnesium content, such as our Plantura Rose Food, is best for this — especially if the Alberta spruce is to remain in the same pot for several years. In general, it is advisable to repot the conifer at least every 3 years. You do not need to fertilise the spruce when you repot it in fresh compost.
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Tip: our Plantura Liquid Houseplant Food containing mainly potassium and nitrogen can be used to remedy acute nutrient deficiencies or as a pick-me-up for your spruce after short stints in a pot. If the spruce is repotted annually, it is enough to just use this liquid food, which is also somewhat easier to apply than granular food.
Alberta spruce as a Christmas tree
The Alberta spruce can also be used as a Christmas tree inside as well as in a container near the front door or on the terrace. Unfortunately, its branches are not so good for decorating as they barely stick out, but a string of Christmas lights will always hold up.
If the Alberta spruce is to be used as a Christmas tree, make sure the indoor location is neither too dark nor too warm. Either way, the Alberta spruce must not be kept inside very long and will require more water when indoors.
- Before bringing the Christmas tree indoors, keep it in an intermediate room where the temperature does not exceed 12 °C for a few days. A cold stairwell or a garage with natural light is suitable for this.
- Once the Alberta spruce has spent a maximum of 10 days indoors as a Christmas tree, slowly reintroduce it to the cold temperatures outside again.
- To do this, place the Alberta spruce in a cool intermediate location below 12 °C for a few days.
- The spruce can also spend the whole winter in this cool room and be taken back outdoors or planted out in May.
Picea glauca ‘Conica’ care
Twice a year, between March and August, give the Alberta spruce growing in the ground an application of a normal NPK fertiliser with a low phosphorus content. If you use the right fertiliser, you will not even need to work compost into the ground. If you use a primarily organic fertiliser, like our Plantura Rose Food, you will only need to fertilise it once a year. This is because it not only provides a suitable ratio of the main nutrients but also magnesium, which is very important for conifers. Spread a layer of mulch around the spruce to prevent the soil around the root ball from drying out in summer.
How to prune Alberta spruces
Pruning is not necessary as Alberta spruces develop their beautiful, conical and dense growth by themselves. That said, they are tolerant of pruning, so feel free to shorten any branches that grow beyond the pyramidal shape. However, be careful not to cut into the brown, un-needled area. This could result in permanent bare patches, as the Alberta spruce is no longer able to sprout from the old wood.
Alberta spruce is turning brown: what to do?
If the needles turn brown at the tip, this is almost always a sign of deficiency — very often a magnesium deficiency. Fertilising regularly with fertiliser containing magnesium will prevent this.
If the needles first turn yellow then brown and then fall off, the pest green spruce aphid (Elatobium abietinum) is probably to blame. An infestation of this pest can be detected by a tapping test. Simply hold a large bowl, a fine net or a cloth under the spruce and tap or shake the branches. The green spruce aphid will drop in response because it expects danger. If you find the aphids on the cloth, you are dealing with an infestation.
Infection with the fungus Lirula macrospora leads to the disease Lirula needle blight. First the needles turn yellow and then brown. Not enough air movement at the site or too much shade can favour the spread of the disease.
In the case of an acute infestation, seek advice from a professional who may apply insecticides or fungicides against the pests mentioned.
Are Alberta spruces hardy?
In accordance with its origin, the Alberta spruce is very hardy, down to -30 °C, and can also withstand heavy frosts. However, potted Alberta spruces should be protected from very low temperatures because the entire pot can freeze through. To do this, wrap the planter in fleece. Make sure that the soil always remains moist in winter and never dries out completely.
Propagation
The easiest way to propagate the Alberta spruce is to take cuttings from well-woody shoots. The best time for this is about 4 to 6 weeks before budbreak in spring.
How to propagate the Alberta spruce with cuttings:
- Cut off 10cm one-year-old side shoots
- Remove the lower needles
- Put them in a pot with seedling compost
- Cover with a transparent film and aerate regularly
- Keep the soil evenly moist
- Optimum rooting at about 20 – 22 °C
- The first roots will form after about 6 – 8 weeks
Are Alberta spruces poisonous?
The Alberta spruce is not poisonous to humans, dogs or cats. Animals do not normally eat the spruce. If swallowed, it can cause constipation in pets due to the non-digestible needles.
Whether in the ground, in a tub or even as a Christmas tree at wintertime, the Alberta spruce can be used in many ways. The Korean fir also makes a beautiful and sustainable Christmas tree.
