Coreopsis: How Tall Do They Grow?

Coreopsis tinctoria, sometimes known by the common name of Dyer’s Tickseed, is a stunning flower conjuring up images of sweeping grassy plains. 

Coreopsis tinctoria now comes in a range of different colors and varieties, but is the more traditional yellow-and-red bloomed variety that I grow each year in my garden. 

In truth, the first year that I grew Coreopsis tinctoria from seed I had little idea about their ultimate dimensions: how tall they grow, how much they spread and how best to display them in my beds. 

In this article we’ll discuss all that to help you properly position Coreopsis in your garden for maximum visual appeal.

How Tall Does Coreopsis Grow?

Coreopsis is a mid-height flower, growing to some 60-90cm in overall height, depending on growing conditions. 

It is also worth mentioning that I’ve had a few “mutant” plants over the least few years which successfully grew much taller, though these were definitely the exception rather than the rule. 

This average height means that they are ideally suited for the middle of your borders, beds or containers. It is simple enough to plant lower-growing flowers in front of them, while enjoying taller plants behind them. 

How Wide Does Coreopsis Grow?  

Coreopsis is generally an upright plant, where most growth goes into getting tall rather than broadening out sideways. Most plants are quite narrow at maturity; think 15-30cm depending on growing conditions.

It is also worth noting that Coreopsis benefits from delicate-looking “feathery” foliage so can look best when planted in a group, closely packed together, rather than having the odd specimen dotted around your garden.

Do Tall Coreopsis Need Staking?

I live in a reasonably windy part of the UK and find that tall, gangly Coreopsis plants can struggle at the start of the season, where they are often hammered by rain and wind. 

While the plants themselves do survive in my experience, the plants often end up growing at odd angles for some weeks until they manage to “right” themselves. The odd plant fails even then, growing at a near-horizontal angle. 

While Coreopsis will grow to flowering without any support, the reality is that Coreopsis grows reasonably tall so some additional support is often a good idea. Fortunately there are a range of options that can work depending on your circumstances.

Firstly, consider planting Coreopsis reasonably densely; not just a patch of Coreopsis growing together but also surrounding them with other plants that will lend some support. 

Secondly, it can be a good idea to place a few garden canes into the ground and to gently gather up the taller Coreopsis stems and tie them in.

Lastly, of course, there are a number of beautiful, ornate plant supports that can be bought online for the ultimate Coreopsis display in summer. 

How Fast Does Coreopsis Grow?

Based on my experience here in the UK Coreopsis can take some time to get started in the spring, but once it gets established the rate of growth can be quite impressive. Furthermore, once the first few buds begin to show you can look forward to literally months of flowers to brighten up your garden. 

To give some specific statistics, last year I planted Coreopsis seeds in March. They took roughly 2 weeks to germinate on my windowsill. I then potted up the seedlings into individual containers and grew them on until planting out in late April. 

They spent a few weeks just getting established, not really doing anything much. Then all of a sudden they put on a growth spurt and seemed to be getting taller by the day. 

Flowers started to appear in July and continued right through to September before the cold weather finally finished them off. 

How Far Apart Should I Plant Coreopsis?

The first time I grew Coreopsis I made the mistake of following the instructions on the seed packet and planting them roughly 30cm apart. With their tall, lanky final appearance I don’t think this showed them off to best effect. I now plant them much closer together, sometimes as little as 10-15cm apart. 

When planted closer together I have found that the relatively fragile stems of Coreopsis support one another, meaning the whole group grows more strongly. Furthermore, a big patch of densely-planted Coreopsis not only looks far more impactful, but can literally be buzzing with bees and hoverflies for months on end. 

Does Coreopsis Need Full Sun?

I have experimented with growing Coreopsis all round my garden. While most seed packets and books will tell you to grow Coreopsis in full sun, my own experience suggests that they will grow well in a far broader range of conditions.

For example, last year I grew a patch of Coreopsis in an east-facing bed backed by a 6 foot wooden fence. This means that while the bed in question gets sunlight from very early in the morning, by early afternoon the sun has moved around and the plants remain in shade for the rest of the day. Despite this they grew well and put on a fantastic display of flowers. 

While I’d personally avoid north-facing borders that get little in the way of direct sunshine, I don’t think you should shy away from experimenting with growing Coreopsis in south, east or west-facing parts of your garden. My own experience in relatively cool and overcast Britain is that they can still flourish. 

Is Coreopsis Perennial?

Coreopsis is half-hardy, and so will be killed off my cold winter weather. As a result Coreopsis is considered an annual. 

Fortunately Coreopsis has a number of benefits over many other annual plants. Firstly, Coreopsis has an incredibly long flowering season, which really rewards your efforts of planting seeds and tending those seedlings early in the season. It is not unreasonable to expect a flush of flowers that will last for months. 

Secondly, is that Coreopsis is quite free-seeding. By this I mean that if you opt not to dead-head your Coreopsis then they will normally scatter fertilized seed over quite a distance. The seeds will lay dormant over the cold winter months, then spring into life the following spring. 

In most cases, therefore, Coreopsis is probably an annual plant that you’ll need to actively cultivate the first year. Every year thereafter it will simply be a matter of relocating any Coreopsis plants growing in odd positions. 

Lastly, it is very easy indeed to collect Coreopsis seeds. The flowers slowly turn to beautiful, sculptural little seed pods that dry to a crispy brown. These pods can be gently crunched between thumb and forefinger where they will release hundreds of seeds.

Ensuring the Coreopsis seeds are nice and dry simply pop them into an envelope, label them carefully with the variety and the year, and you’re ready to grow more the following year.

Should Coreopsis Be Cut Back?

Coreopsis can be a bit of a straggly plant, and if not staked may find itself eventually falling over. This can look messy, and of course can be inconvenient if they fall onto garden paths, lawns and so on.

Under these circumstances Coreopsis may certainly be cut back, though appreciate you may be removing stems with flower buds so you may limit the eventual display. 

At the end of flowering you really have two choices. Either leave the plants to go to seed, to guarantee a fresh supply of seeds or seedlings the next year, or just pull up the old Coreopsis plants and pop them on the compost heap. 

Coreopsis is reasonably shallow-rooted so they’re very easy to pull up and dispose of at the end of the season. 

Whenever you choose to do it you’ll likely want to remove last year’s plant before the following spring. 

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