Quote from Lee Garden Ninja on 9th August 2025, 7:52 am

Hi @silva

Thank you for your excellent question from Serbia. Don't worry about the lack of local expertise, that's why the Garden Ninja community is here to help! What you're experiencing with your Chamaecyparis lawsoniana 'Ivonne' is actually perfectly normal for young conifers, although I completely understand your confusion about the conflicting information available.

The key thing to understand about conifers is that they put on most of their vigorous growth within the first 5-10 years after planting, which is exactly what you're seeing. That impressive 50cm per year growth rate you're experiencing is typical for young, well-established Lawson cypress cultivars in good conditions. However, this rapid growth rate will naturally slow down significantly as the trees mature, which is why many sources give what seem like contradictory ultimate heights.

Why Growth Information Varies So Much

The confusion surrounding the ultimate heights of cultivars like 'Ivonne', 'Golden Wonder', 'Stewartii', and 'Lane' stems from several factors that influence how these trees perform in various situations. Firstly, many of these cultivars are relatively new in horticultural terms, so we don't have decades of real-world data on their ultimate potential. What we do have are projections based on their early growth patterns and parentage.

Your growing conditions in Serbia sound absolutely ideal for Lawson cypress - that south-east slope with terraced levels and drip irrigation is providing excellent drainage whilst maintaining consistent moisture. These are the conditions where these cultivars will achieve their maximum potential, which might well exceed the conservative estimates you're finding in reference books that often quote minimum rather than maximum sizes.

Realistic Expectations for 'Ivonne'

Based on your current growth rate and the performance of similar cultivars, I'd expect your 'Ivonne' specimens to reach somewhere between 8-10 metres over the next 20-40 years. The lower estimates you're finding (6-8m) are likely based on less favourable growing conditions, conifers that are pruned into shape or more conservative projections.

What will happen over the coming years is that annual growth will gradually reduce from your current 50cm per year to perhaps 20-30cm annually in years 10-15, then down to 10-15cm per year as they reach maturity. This is completely normal behaviour for conifers and doesn't indicate any problems with your plants or growing conditions. You can always prune and trim your conifer as long as its back to green wood only, this will keep its size under control. You should definately check out my confiers guide here.

Managing Long-Term Growth

Given your excellent growing conditions and the vigorous start your trees have had, I'd actually plan for the upper end of the size range. This means considering how they'll fit into your landscape design over the coming decades. If space becomes an issue, Lawson cypress cultivars generally respond well to light pruning to control height and spread, though this is best done little and often rather than dramatic reduction.

Your Lonicera nitida ground cover is an excellent choice for erosion control and will also help compete with any weeds whilst your conifers establish their root systems. As the cypress trees mature and their canopies expand, you may find the Lonicera becomes less vigorous in the increased shade, which is perfectly natural.

Keep Us Posted on Progress

It's always fascinating to hear from gardeners in different climates and conditions, especially when working with cultivars that lack extensive long-term data. I'd love to hear how your 'Ivonne' specimens develop over the coming years, as your experience will be valuable for other gardeners considering these cultivars.

The fact that you're seeing such vigorous growth suggests you've got the growing conditions spot on, so I wouldn't be at all surprised if your trees exceed those conservative height estimates you've been finding. 

Further Reading: Conifer Forum Posts

For more specific conifer advice, check out these helpful forum discussions:

• HUGE conifer tree - can I prune it back? - Understanding why conifers can't be hard pruned once mature
• Will my conifer grow back? - Why conifers don't regenerate from old wood
• Dying conifers turning brown - Troubleshooting brown patches and conifer health issues
• Conifer watering and pruning advice - Essential care tips for potted and established conifers
• Brown Christmas Tree - can my conifer be saved? - Dealing with dehydration damage
• Unruly conifers - Managing overgrown conifer hedges and trees
• Evergreen as a fence - Choosing the right conifers for hedging

Essential Blog Guides

• How to Prune Conifers: Ultimate tree care guide - Comprehensive conifer pruning guide
• How to cut, prune & trim hedges - General hedge maintenance including conifers

Happy gardening!

Lee

Quote from silva on 9th August 2025, 10:48 am

Hi Lee,

Thank you so much for such a quick and detailed reply – we really appreciate it. Your explanation has cleared up a lot of our confusion about growth rates and ultimate height, and it’s reassuring to know our trees are behaving normally.

We do have one more question regarding Phytophthora lateralis. We know it is a serious disease and that it is already present in forests and other habitats. What we would like to know is: given that we have 35 specimens of Chamaecyparis lawsoniana ‘Ivonne’ planted together, is the risk of an infestation higher, and should we expect it could happen? We should also mention that our Chamaecyparis lawsoniana ‘Ivonne’ are growing on their own roots – they are not grafted.

We’ll make sure to post regular updates on how our trees are doing – we’re genuinely happy and excited to share their progress with everyone here, especially since there’s so little long-term information on this cultivar.

Thanks again for your time and for creating such a welcoming place for gardeners from all over the world. 🌱

Best wishes 😊