Western arborvitae can be propagated in winter from dormant hardwood cuttings. First choose a place where the growing medium will remain above freezing and you can check it through cold nights and sunny spells. A mature outdoor tree can withstand weather that would freeze a shallow tray of cuttings. On the other hand, a windowsill over a radiator can dry the cuttings before they root. Use a protected spot with light, drainage and a way to monitor conditions. Wait for actual roots before treating a cutting as a young plant.
Choose one healthy stock plant at a time
Confirm that the plant is western arborvitae (Thuja occidentalis). Similar common names are used for other evergreens, and their best cutting stage can differ. A cutting carries the characteristics of its own stock plant. If you want more plants of a named cultivar, identify that cultivar before harvesting. Some cultivars root more readily than others under the same conditions. A labelled trial is more informative than a tray of branches gathered from several unidentified trees.
Look for firm, mature growth from the previous growing season. Inspect the foliage and the base of the proposed cutting. Pass over shoots with injured bark, blackened sections or soft, actively extending tips. If much of the parent plant is drying back or the tree is under obvious stress, leave it alone and look for healthy material elsewhere. Avoid stripping a single conspicuous part of the crown. Use a clean, sharp tool and gather only the number of shoots you have room to handle.
Label the tray with the date and the plant or cultivar name. If you are comparing two sources, label individual rows or containers before you put the shoots into the medium. The position may matter as much as the source: a tray's outer cells can dry or cool faster than its centre. For other cutting stages, see the guide to propagating arborvitae from cuttings. The steps here apply specifically to winter use of mature wood.
Check the propagation space on a cold night
A light, sheltered propagation area with minimal heat can work if the medium stays protected from freezing. Check the night temperature next to the containers. A glazed porch can warm on a sunny afternoon and become coldest along the window after dark. A tray in an unheated greenhouse can also freeze. If your only options are a freezing balcony and a hot indoor windowsill, wait until you have conditions that you can control.
On exposed sites in northern Ukraine or in the foothills, allow for repeated cold nights and cold pockets near doors or glazing. In a southern garden during a thaw, observe the same space at midday and again near dawn. Clear lids and covers can warm quickly in direct sun while the growing medium cools later. Check for draughts and find where excess water will go when you irrigate. Make these observations before cutting material from the plant.
Prepare hardwood cuttings and insert them promptly
Identify the base and keep the upper foliage
A heel cutting has a small piece of older wood at the base where the shoot joined the branch. It is one option for western arborvitae. If a long strip of bark tears free, trim the ragged material cleanly. Keep the cuttings cool and protect them from drying while you prepare them. Remove foliage from the part that will go under the surface, keeping the healthy upper foliage. Work when the branch is accessible and you can handle it without a severe freeze.
Keep the medium moist with air around the base
Use a fresh commercial rooting mix or an airy medium with a suitable coarse component such as perlite. Heavy garden soil or a highly fertilized potting mix makes it harder to manage the small rooting area. Moisten the medium evenly before inserting the cuttings and allow the water to drain. Make a hole first, place the base in it, and close the medium gently around the stem. Give neighbouring cuttings room for light and inspection without foliage lying in a mat across the tray.
A rooting treatment is optional. If you use one, read its directions for the type of cutting you are preparing. Avoid applying the instructions for a soft green cutting to dormant wood by guesswork. Different cultivars and treatments can change the result. A cutting on a porch may root at a different pace from one grown in a nursery with controlled conditions. Keep separate labels if you compare a treated group with an untreated one.
Manage moisture through winter
Feel the medium below the surface before adding water. Condensation on a clear cover tells you about the air around it. There can still be a drier cell underneath, or a tray that is saturated in its lower half. If water remains in the catch tray, empty it and check the holes. If the outside cells dry first, check those areas separately. Some protected setups maintain enough humidity without frequent misting. Keep covers from touching the foliage and allow excess moisture to escape.
Imagine two trays prepared with the same cuttings. One stays evenly moist and the other shows a frozen edge beside the window at dawn. Move the exposed tray to a place you can control before changing the mix or buying another rooting treatment. In a different situation, a wet tray develops several cuttings with dark, soft bases. Isolate damaged cuttings and examine drainage and air movement. Both examples call for checking conditions before you add anything to the medium.
Keep a short record of changes
Record the overnight minimum, the condition inside the medium, the tray position and any changes to the cuttings. If a tray catches drips from a cover, move it away from the drips and check whether that part dries more evenly. Change one factor at a time so you can compare. When you spot roots on several stems, write down which plants and positions they came from. The record helps you plan a later batch with better information about your own setup.
Recognize roots and make the transition slowly
Green foliage can persist before roots form. A swelling or callus at the base is also an earlier observation than a visible root system. Look for roots against the side of a transparent container or near a drain hole. Avoid pulling up the entire batch. If you need to examine one sample, lift the plug intact and leave the medium around the stem. Give very fine new roots time to grow before you move the cutting.
Once the cutting has enough roots to hold the medium during handling, ease it into lower humidity and more light. Pot it individually when you can handle it without breaking young roots. Let it settle before exposing it to stronger sun, dry wind or cold nights. Leave newly rooted plants protected when the forecast requires it. Before moving into a permanent place, read how to check soil for conifers and consider the drainage, future canopy and room for regular care.
Feeding established arborvitae
Complex fertilizer for coniferous evergreens, granules
Consider these dry granules for conifers later, once a young tree is established, growing and has a nutrient need. Unrooted cuttings need stable conditions and a porous medium. The fertilizer instructions distinguish spring planting from feeding during active growth and include a specific caution for dwarf cultivars.
Choose the applicable method by stage and plant size, then compare the 1, 3 and 4 kg packs on the product page. Estimate the amount for your established plants before choosing a pack.
Frequently asked questions
It can work if the medium stays above freezing and you can manage sudden changes in temperature and moisture. Check the temperature next to the tray at night. If hard frost can reach the roots there, choose a more protected location or wait for another propagation window.
A small heel is one option for western arborvitae. Choose healthy mature growth and assess the cultivar and conditions as well. If you want to compare two cutting styles, keep the rest of the conditions as similar as possible and label the groups.
Colour alone cannot show whether the cutting has roots. Wait until you can see an established root system that can be moved with its medium. Then introduce it to new humidity, light and outdoor conditions gradually.
