Why doesn't my green grass turn colour in the autumn?

It isn’t like grass leaves are similar to conifer needles. So what gives?

If you look around you in the fall, not all deciduous trees’ leaves turn the same color; most oaks, in fact, just turn as brown as the grass you’re thinking of. While at the same time, many grasses do indeed turn bright yellows, oranges, and reds. There’s just more variety out there then you may be aware of.

Grass is only very superficially similar to conifer needles.

But both grass and conifer needles do turn brown and wither and/or fall, just not all at once like on deciduous plants.

Mt grass turns brown in the summer if not watered, but in the autumn, with the increased rain it remains vibrant green all winter. So does everone elses lawn around here near the Pacific Northwest.

Yes, but if you get down and examine the individual grass plants, you should find that they have some live, green leaves and others that are withered and yellow.

Yes but the Oaks due lose their green colour while my grass remains green throughout the winter. A clear exception around here though is the Arbutus tree which only lose a portion of their leaves each year.

But does this grass turn as a result of coldness or shorter daylight time as a result of the autumn season or is it because of lack of water which could occur in any season.

I’m not sure why you’d think grass should change colour in the autumn. Out of the vast array of green leafy plants, a pretty small proportion change colour and shed their leaves in autumn. Grass isn’t deciduous, just the same as plenty of other garden plants aren’t. It’s not just conifers that stay green through the winter.

Yes. Deciduous trees change color because the plant cuts off all nutrients to the leaves and the chlorophyll fades and no longe colors the leaf green. Grass doesn’t have this mechanism.

Grass does turn brown in the winter around here–you just usually don’t see it because it is covered with snow at the time.

Many grasses do go dormant in the winter, depending on the climate. Many others do not. Some do turn colors in the fall for the same reasons that some trees do; others do not. There are as many as 10,000 spp. of grass*, and up to 100,000 spp. of trees*; there’s gonna be some variation.

The point being, OP, that reason your grass doesn’t follow the universal rule is that there is no universal rule.

*Added to this, the fact that words like “grass” and “tree” are artificial distinctions made by people; nature makes no such distinctions. Look at the span of varieties of such genera as Euphorbia, Nicotiana, and *Bambusa *for an idea of how gray such areas can be.

Most of what follows is shaky recall of college botany, but the vibrant reds are anthocyanin pigments, and vibrant yellows are flavanoids. When colder weather and shorter day length stop green chlorophyll from being made, these pigments are left behind. I’m less sure what these pigments are for, they may absorb more light, some that gets missed by chlorophyll, and “feed” some solar energy to the chlorophyll, so the tree gets more energy over all. Any plant that doesn’t have pretty colors, is because that plant doesn’t make and use these accessory pigment.