This post is about my observations from two of the cats who most enjoy the grass. I think think they enjoy the psychoactive effects. My following post will explain my experience with consuming it.
Living in South Africa with a fully indigenous garden; Crabgrass is something that I have come to have a fairly strange-if-good relationship with. While it is slightly invasive, it is very easy to control (pulls out fairly cleanly in moderate dry soil conditions) and strangely enough does not seem to fight much with other low growing plants until a fair few tufts are growing in close proximity. Since they are not too much of a hastle I leave them, purely because the cats absolutely love eating the leaves. I find crabgrass compelling for some reason, it's clearly been a friend of animals for a long time.
I am unsure of the exact taxonomy/name/details of the common variety here; However will try find that out in a few weeks time from a professional friend.
Plant conditions/locations : The plants in my garden are in a wide range of conditions, usually only on the fringe of paths or borders, which makes them easy to observe, and for the cats to eat. Exposed to harsher conditions (or lack of some direct light), the leaves tend to become blue, sometimes developing an almost dusty grey-green-blue appearance, the cats do not eat this. Overwatered they sulk and turn a yellow colour, root damage I'm sure; this too the cats avoid, even after they recover it seems. Some insects seem to damage the leaves and occasionally slugs will take a bite, usually resulting in a purple-red colour on the leaf, eventually the whole plant follows suit; cats will not even consider them.
The best plants are ones on the borders of rich soil, but with a more sandy consistency underfoot. Watered enough to have a damp->dry transition every day or two. Filtered canopy light or 1-2 hours of direct. These grow prolifically and are the ones most enjoyed by the cats (as seen by them seldom having many intact leaves!). Spring/cool summer is when they seem to be most attracted to the plants with their rich green transitioning to lighter green at the tip.
Now lets explain the whole cat thing; It's odd. If you take a 'branch' of leaves from the plant (they snap off nicely if growing well) and show it to a cat who knows; they will recognise it from ~10m away (I recently taught a friends cat with a 'branch' of 5-6 large healthy leaves from a plant my cat had been muching on, the next few days I tested how much he really enjoyed it
), once close they tend to sniff along the leaf margins to find leaves that contain what they want (i.e if they have not noticed the leaf is damaged, they will smell it but seem to not find what they are looking for, or if there are some blue leaves mixed in, and skip that specific leaf). Once finding a good green leaf, they will eat the top half of it. Only the top half of the leaf is eaten. Every now and then they will eat the green seeds, but they don't smell them or seem especially interested. The leaves have sharp margins, so a cat takes a few weeks to develop a good method of biting off the exact portion they want.
During winter they also seem to enjoy the leaves, but once summer gets too hot and the plants suffer a heat stroke or something, they will not be too enthused about them (but if you find some crunchy fresh leaves, they will happily much them after a quick sniff). A medium sized, very healthy cat seems to like 20 medium-large leaves before deciding to stop. If only given a few leaves, they will try to get me to follow them to other plants in order to give them easy access to more. While many people seem to think that they only eat 'grass' when ill, they actually seem to eat less crabgrass, while when happy and healthy they will actively pursue much larger amounts!
Now that I sound slightly nuts... on to the experience post!