To progress in Grounded, one of your priorities is to make a bow and a very large reserve of arrows, in order to kill the worst enemies while being cowardly stashed high up. That'll teach those damn Wolf Spiders! At least that's what you're going to tell yourself for a second before she leaps to your hiding place. It works on Orbitels, Ladybugs and lots of other enemies though, so it's still fantastic.
But before you get to that, you need thistle needles. You can find this purple flower, with its stem and leaves covered with thorns in different corners of the garden, it is not really rare, and it is easy to spot thanks to its height. Each thistle is covered with 70 needles , if you take the time to collect them all by climbing the leaves. These needles reappear quite quickly, after only one or two days. Suffice to say that it is easy to make a large stock.
Map of Thistles
This is not an exhaustive list, but there are 5 thistles quite close to the starting point. The problem is that almost all of them are in a danger zone. Those marked in red on the map, are in areas full of dangerous enemies, even in a toxic area. It is therefore better to turn to those marked in green, which are close to each other. The best choice is by far the one a little to the south, since there are no enemies nearby, and as a bonus, there are plenty of Gnats circling around. You need to kill them to craft a Gas Mask and the Bow, which means you'll kill two birds with one stone.
The thistle a little further north can be harvested without too many problems, if you avoid being spotted by the Bombardier Beetle which wanders nearby. But in the worst case, you will be safe from its projectiles, once high in its leaves.
If you want to know how many needles you need, know that it takes about 120-150 arrows (that's as many needles) to kill a Wolf Spider solo. You can pick up the majority of them afterwards, on the ground, but there are always a few that get lost after bouncing. If you're playing multiplayer, plan for more.