Sumac trees: varieties, cultivation & care
Sumac trees are magnificent trees for autumn colour. Find out all you need to know about this special tree here, from how to cultivate it to keeping its growth in check.
Sumac trees are counted among pioneer plants. They are often found growing along roadsides and embankments, but they grow well in gardens as well. Read on to discover some of the different sumac varieties, find out how to cultivate sumac in your garden or in containers as well as how to use sumac berries.
Sumac trees: origin and properties
Sumac trees (Rhus), also spelled sumach, belong to the sumac family known as Anacardiaceae. The Latin name Rhus derives from the Greek word rheo meaning ‘to flow’. This likely refers to the milky sap that flows out from the tree upon injury. There are about 200 species of sumac worldwide, distributed in the tropics, subtropics and temperate zones. The ornamental species known as staghorn sumac (Rhus typhina) is originally from the eastern part of North America.
Sumac trees grow as small trees with a single stem or as large shrubs with multiple stems. They generally grow 4 to 6m tall and wide and, in exceptional cases, even up to 10m. In their early years, sumac trees have an annual growth of 30 to 40cm. As they age, their growth decreases sharply. These deciduous trees form thick branched shoots. Fresh, new shoots are brown and velvety, and as they grow, they darken in colour and amass their milky sap. Sumac leaves are green on top with a grey tinge on the underside and typically lanceolate, pinnate and up to 60cm long. When the leaves change colour in autumn, they turn bright shades of yellow, orange and scarlet, providing spectacular autumn colour.
The sumac’s light green, upright, flower panicles grow up to 20cm long and bloom from June to July. They provide abundant nectar and pollen for bees and other pollinators. After pollination, the panicles fill with dark red, velvety seed heads. These remain on the plant through winter, adding a pop of colour to the garden in the bleak, winter months. Sumac berries taste sour and are sometimes added to vinegar to make it even sourer.
Sumac tree fruits and sumac spice
Sumac tree seeds are edible, and from late autumn to winter, sumac fruit stalks can be harvested and dried. In North America, sumac lemonade, or Rhus juice, is a tart, refreshing drink that has been popular for years. It is made by steeping sumac fruits in water and adding sugar. The dried seeds are also sour and aromatic, and are typically used as spices. Sumac spice is made from the seeds from Sicilian sumac (Rhus coriaria) and is simply called “sumac”. It is commonly used in za’atar spice blends and in Middle Eastern cuisine with salads, fish and meat.
Are sumac trees poisonous?
Except for their ripe fruits, sumac trees are slightly poisonous. For herbivores, such as horses and rabbits, eating large amounts can cause stomach cramps. Dogs can also become ill after nibbling on sumac leaves or other parts of the tree. The milky sap that flows from the tree’s wounds also irritates our skin, so wear gloves when pruning and working with sumac trees.
Sumac tree species and varieties
There are several species and varieties of Rhus trees, which differ significantly in terms of leaf shape and growth height. Two common species are staghorn sumac (Rhus typhina) and scarlet sumac (Rhus glabra). Here are some of the most popular varieties of this ornamental shrub, each of which is hardy down to -20 °C.
- Rhus typhina ˈDissectaˈ: also called cut-leaved stag’s horn sumach, this sumac tree has finely pinnate and fern-like leaves. It grows up to 4m high and up to twice as wide.
- Rhus typhina ˈTiger Eyesˈ: a small stag’s horn sumac tree variety growing 1.5 – 2m tall. As their leaves change colour, they cover every autumn hue.
- Rhus glabra: scarlet sumac has a growth height of 2 – 3m, and, unlike other sumac species, its shoots are completely smooth. In autumn, this sumac variety bears fiery orange-red leaves and burgundy fruit clusters.
- Rhus glabra ˈLaciniataˈ: this sumac has comparatively weak growth and bright red autumn colour. Its growth height and width reach 2 – 3m.
Danger of confusion: at first glance, it is easy to confuse a sumac tree with the tree of heaven (Ailanthus altissima). Both trees’ pinnate leaves, flowerheads and velvety shoots are similar and make the two trees difficult to tell apart. However, the tree of heaven is much taller at over 20m, and its fruiting branches form winged seeds, like maples (Acer sp.) rather than cobs.
Planting sumac trees
First and foremost, you need to find the right location for your sumac tree. Look for a spot that is sunny with well-drained, moderately fertile and somewhat sandy soil. It is also important to choose a spot that allows for a minimum planting distance of 3m, so that your sumac tree has enough room to grow. Other than that, this ornamental tree is undemanding and does well in moderately dry or moist sites, whether the soil is acidic, alkaline, sandy or clayey.
The best time to plant sumac trees is in autumn or early spring. As the trees transition into winter dormancy from October to November, they transpire less water and can focus their energy on growing new roots. If you plant your sumac tree in spring, water it regularly for the first few weeks while the sapling establishes itself. While it is possible to start a sumac plant from a seed, people tend to plant saplings.
Before planting a sumac sapling, prepare the planting location. To do this, loosen the soil over a large area that extends further than just the planting location. Then, dig out a planting hole and place the saplings plants in the excavated hole. Add some organic slow-release fertiliser, such as our Plantura All Purpose Plant Food, if necessary.
If the soil is too sandy, mix in some high-quality potting soil such as our Plantura Organic All Purpose Compost. Adding an organic fertiliser such as ours to the soil supports your sumac tree by providing it with long-term nutrients. After placing the sapling in the planting hole, fill in the hole with the excavated soil, and water the sumac sapling thoroughly.
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Caution: as sumac trees are highly invasive and self-propagate via root runners, we strongly recommend including a root barrier when planting these trees. The root barriers should reach at least 60cm deep to effectively keep the sumac tree runners from spreading.
Sumac tree care
Sumac trees are very easy to care for throughout the year. They only need watering during extremely dry summers, especially during their first year of growth. Once a sumac tree has established a strong root system, it can meet its water needs by itself. Sumac trees grow shallow roots, so avoid digging or hoeing directly under these trees, as this can injure the trees’ roots. If your sumac tree is growing in poor soil, apply a bit of fertiliser annually when the leaves begin to emerge in spring.
Apart from removing the occasional problematic branch, pruning sumac trees is rarely necessary. Staghorn sumac trees can simply be left to form their dome-shaped crown all by themselves. If you do need to prune your sumac tree, the right time of year is early spring. Be sure to wear gloves to protect your hands from the skin-irritating sap.
Tip: if a sumac’s fleshy, shallow roots are injured, they will focus their energy on forming root runners. Therefore, it is best to avoid harming the tree’s roots to allow them steady and strong growth throughout the years.
Sumac shrubs in pots
Only low-growing varieties of staghorn sumac, such as Rhus typhina ˈTiger Eyesˈ, are suitable for cultivating in pots. When planting a sumac shrub in a pot, be sure to choose a large planter with a volume of at least 20L. Ensure the planter has plenty of drainage holes, and add a roughly 5cm thick drainage layer made of coarse gravel, sand or expanded clay to the bottom of the container. Once the pot is ready, plant the staghorn sumac in loose potting soil such as our Plantura Organic All Purpose Compost, for instance. Our compost retains sufficient moisture thanks to its high compost content, and is entirely peat-free. Our compost also contains important nutrients that promote strong tree growth. Sumac trees grow rapidly when they are young, so your tree will need a new larger pot about every 2 years. And as there is a limited amount of soil available to a potted tree or shrub, they use up the soil’s nutrients quickly. So, when repotting your sumac tree, be sure to give it another dose of fertiliser.
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Overwintering sumac trees
Sumac trees are hardy woody plants. They do not require any protection from the cold when planted in the garden.
However, potted sumac shrubs are another story. A potted sumac runs the risk of its soil freezing through along with its roots, which ultimately kills the plant. To help prevent the soil from freezing, wrap a fleece around the container, add a thick layer of mulch over the soil and place the container on top of insulating boards. Another great option is to overwinter potted sumacs in a cool garden shed, summer house or in a sheltered garage. The overwintering location should be bright and cool. Remember, although potted sumac shrubs are more susceptible to the cold, they are still relatively hardy. Therefore, it is fine for the overwintering temperatures to drop slightly into the minus range. In fact, overwintering inside a house or conservatory is discouraged, as it is much too warm for a staghorn sumac. With the occasional sip of water, your potted sumac tree will ride out the winter just fine.
Propagating sumac trees
Sumac trees can be propagated by stolons, root cuttings, cuttings or by seed.
To harvest stolons, i.e. root runners, ready for propagation, use a spade to sever the stolon’s connection with the mother tree. Replant the sumac stolon cutting in its new location with a planting distance of 3m. Like with planting, it is best to propagate in autumn or early spring, before the leaves emerge.
Sumac trees can also be grown from root cuttings. Many nurseries use this method to propagate their varieties. To harvest root cuttings, dig up a thick, fleshy root, and sever it from the mother tree. Place the root cutting in a moist, well-drained growing medium. With time, it will grow its own sumac sapling.
Harvesting cuttings from sumac trees is perhaps the gentlest method of propagation. In winter, select a healthy young shoot that is about 15cm long and cut it with a clean pair of garden shears. Plant the cutting about 7cm deep in a loose and permeable soil. Our Plantura Organic Herb & Seedling Compost is a great option for this, just mix in some sand or perlite to further increase the soil’s permeability. Keep the planted cutting in a bright, cool place with temperatures between 6 and 12 °C. Roots should grow within a few months. Keep the soil consistently moist during this time.
Harvest sumac seeds in October, when the red cobs are mature. Cut off the whole cob and allow it to dry indoors until the seeds fall off on their own. Growing a sumac tree from a seed is not simple. It requires a few weeks of patience, as the seeds remain dormant until exposed to a cold stimulus that kicks off germination. Here is how to sow sumac seeds:
- Soak sumac tree seeds in hot water for 24 hours
- Make a 1:1 sand-soil mixture, and add the seeds
- Pour the mixture into a plastic bag and place in a refrigerator at 4 – 6 °C
- Keep the seeds in the refrigerator for 4 weeks
- Next, sow the seeds at a depth of 0.5cm in a low-nutrients substrate, such as our Plantura Organic Herb & Seedling Compost
- Place the sowing container in a bright and warm location at 15 – 20 °C
- Keep the seeds moist for the next few weeks until they germinate and prick out the seedlings as soon as the first true pair of leaves appear
Tip: remove any sumac seeds that begin to germinate while still in the refrigerator and transfer to potting soil.
Keeping sumac in check
As pretty as staghorn sumacs are in autumn, they are not always welcome in gardens. As previously mentioned, sumacs are a highly invasive species. For this reason, it is important to be very thorough when removing a sumac tree — new trees can sprout from any fleshy roots that are left in the soil. Unfortunately, sumac trees sprouting in the garden can also be the work of birds dispersing the seeds when they visit.
Even for those gardeners who enjoy keeping a staghorn sumac, the root runners can quickly become a nuisance. To prevent root runners from spreading and forming new saplings, do not prune a sumac tree too much or injure the roots. Lay a deep root barrier when planting to avoid problems with runners in the future. For root runners that are already a problem, one good way of eliminating young shoots is by mowing them regularly. Cut larger and already woody saplings with a spade, removing as many roots as possible.
Ornamental trees and woody shrubs with bright autumn colours are lovely to have in your garden. Discover more vibrant perennials in our special article on shrubs and trees with intense autumn colour.