Achillea Terracotta height

Swooping Swallow

Can anyone confirm the height this plant can be expected to grow to? Of course, it depends on the conditions in which it is grown, but some websites state it will achieve a full height of 1 - 1.5m, while others state it will grow to 75cm.
https://www.rhs.org.uk/Plants/72358/i-Achillea-i-Terracotta/Details
https://www.sarahraven.com/products/achillea-millefolium-terracotta

I ask as I've just bought some from a well known nursery and on arrival the plant is Achillea millefolium Terracotta, which is listed on the Sarah Raven website as 75cm high. However, the nursery from whom I bought the plant lists it as Achillea Terracotta. Is it the case that the millefolium varieties are shorter, or are they the same as the non-millefolium listed varieties?      

Fairygirl

It grew to about 3 feet for me in a previous garden. It really just depends on conditions and how it's being grown. Same as many plants.  Perennials of any kind also take a few years to reach maturity. 
The correct name is A. millefolium. Terracotta is just the variety. Often, varieties will just be listed without the millefolium. 

Swooping Swallow

It grew to about 3 feet for me in a previous garden. It really just depends on conditions and how it's being grown. Same as many plants.  Perennials of any kind also take a few years to reach maturity. 
The correct name is A. millefolium. Terracotta is just the variety. Often, varieties will just be listed without the millefolium. 

That's useful to know. 3ft equates to about 90cm, which is what I was hoping for (conditions permitting). I wonder why listed plant dimensions can vary so much from website to website? Does this simply reflect the range of heights a plant can grow to and the impossibility of giving a definitive figure? Given the size of the prairie border plants I saw at Wisley last year, I can understand why RHS trials have probably found Achillea's can grow to 1.5m, but for us mere mortals....   

Did yours have soil enriched with organic matter or quite poor soil?  

Fairygirl

It's the same for virtually any plant - regional variations due to climate and soil make a big difference in heights and widths. 
Mine would have been in fairly average soil, and I always grew Achilleas in the sunniest, driest spots I had, often having to use raised beds to aid drainage. I live in a very wet part of the country, and always garden on clay soil, so growing plants that like drier conditions can be difficult unless soil is amended.
Our season starts later too, so plants are slower starting into growth, and autumn arrives in early August. That also has an effect on the height they gain in a season.

Wibble

I have a couple of Achillea, both in their 2nd year, both around 3 feet high. They got to around that height last year too - they have produced a thicker clump this year, rather than changed in height. I’m on clay, lot of stone in the mix, drainage not superb. They seem very happy with that!

Swooping Swallow

A height of 3ft should work well as they will be planted with Echinacea White Swan in front, which (supposedly!) grows to about 60cm.  The soil is dry and sandy, but lots of well rotted manure has been added. A mulch (probably composted bark, but it seems to be unobtainable at the moment) will be added. Hopefully, they'll get to 3ft with those conditions. 

februarysgirl

I bought a couple of 9cm Achillea Terracottas from Sarah Raven last summer and planted them in my west facing raised bed March just gone. Didn't do anything special with them, the beds are filled with Wickes topsoil and I didn't add any compost but they are covered with bark chippings. I've just been out to measure them and the tallest stem reaches 103cm. The spread (which I haven't measured) is pretty impressive as well given their size when planted. I am toying with the idea of removing one of them as they turned out way bigger than I was anticipating. Have to say, they've been insanely popular with pollinators.

TheGreenMan

I planted this one in late April. 

I’ve just been out to measure and it’s 97cm from base to tallest stem. 

Planted it (slightly improved clay; raised bed so drainage good) Covered the base with bark. Left it.

Fairygirl

Richer soil, and moisture and heat at the right time, will tend to produce taller, lusher plants. 
Not always a good thing, but it's the reason for the variations in different parts of the country. 
If you were growing them in Shetland, they'd struggle to be half that height. They'd struggle to be upright too 

februarysgirl

@Fairygirl I'm having issues with uprightedness 😂 I ended up putting plant support around them but they're still all over the place (much like the nearby Heleniums which are equally tall). I'll definitely be putting support around them after their pruning next spring rather than leaving it until they start getting wayward!

Fairygirl

The easiest way to support any planting - is to use other planting 
I don't mind a bit of flopping - within reason - but if I have some branches lopped off buddleias or spireas or something similar, I stick those in to keep the odd wayward stem in it's place. Less visible.
Heleniums get quite excitable and fancy a bit of world domination, so, even though there's a Euphorbia in front of mine to bolster them,  they usually need a bit of containing around now, especially if it's been a bit wild and windy. I moved some to another border earlier this year, and that clump has a Phormium to keep it in check