Nature counts all the time: tree rings, the angles of petals or leaves, the packing shapes for seeds.

Venus flytraps even count the number of their spikes that were moved during a certain interval of time to know whether to close or stay open.

Lots of animals have been verified to understand and use abstract count which is what numbers are at their basics.

Plants are much less adaptive than animals by definition. The problem isn’t whether they know numbers but how do you even test what plants “know”.

Well, in a very primitive and non-accurate sense, it counts/measures the number of (photo synthesis generating) photons hitting each leaves, and then grows in directions that maximizes its photo synthesis.

Since a tree has a much lower number of branches and leaves than there are photons, there has to be some aggregation of information involved in this computational process.

They don't design spaceships either.

Of which we are aware.

mycelia microcosm intensifies