No, you can't just scale up a daisy.
Or.
The Square-Cube Law strikes again.
The Square-Cube Law says that as you increase the size of a thing, it's volume grows faster than its surface area. Specifically, the volume is cubed while the surface area is squared.
Think about a daisy as a basically a big tube, a cylinder. Let's say 10 cm high and 1 cm in radius. That has a volume of 31 $cm^3$ and a surface area of 69 $cm^2$. Now double its size: 20 cm high and 2 cm radius. That has a volume of 251 $cm^3$ and a surface area of 276 $cm^2$.
Notice something? The ratio of the surface area to volume dropped. It went from $\frac{69}{31} = 2.2$ to $\frac{276}{251} = 1.1$. If we double the size again to 40 cm by 4 cm, it drops again to $\frac{1106}{2011} = 0.55$. Every time you double the size you halve the ratio of surface area to volume. At 10 m high and 1 m around (or 1000 cm x 100 cm) you're down to $\frac{691150}{31400000} = 0.022$. 100 times taller, $\frac{1}{100}$th the surface area-to-volume ratio.
Ok, so what? A lot of biology depends on this ratio is high. For example, photosynthesis depends on the surface area of the leaves. A 10 cm high daisy has plenty of surface area to fuel its volume. But a 10 m high daisy now has to fuel 1,000,000 times more daisy (volume) with only 10,000 times more photosynthesis (surface area). It will starve. Large plants have developed more and smaller leaves (smaller in comparison to their size) to increase their surface area. This is why you'll see small plants with a few large leaves, but large plants like trees with many, many small leaves.
Simple circulatory systems also depend on a high surface-to-volume ratio. Rather than having a complex system that delivers food, carbon dioxide, and nutrients directly to the cell, many depend on simple diffusion to get these molecules from outside the plant to the innermost cells. Or from a plant's vascular tissue to every cell. This works in a small plant with relatively few layers of small cells. But when you scale up the distances become too great for diffusion to be effective and the cells further from the surface of the plant will suffocate and starve. A more complex vascular system is necessary. Or, in the case of trees, reducing your volume of living cells by allowing your interior cells to die and form heartwood.
Then there's pumping water and nutrients up from the soil to the top of the plant. In a small plant this is easy and requires little specialized biology, the distance is small, the tubes are narrow, so capillary action will handle it. But at 10 m tall this is not enough. Specialized mechanisms for getting water to flow that high are necessary which trees have but daisies do not.
Structurally as well, a daisy will collapse under its own weight. Trees and woody plants differentiate their trunk into bark for strength and protection, phloem for transporting nutrients, xylem for transporting water, and the heartwood made of old mineralized xylem cells to protect the center of the tree and provide more strength. A daisy lacks these specialized structures, or they're not so well developed. At its size, it does not need them. Much of its strength comes from water pressure, this is why small plants droop when they aren't watered, but trees do not.
And so on. In order for this to work your giant daisies have to have evolved to do all the things trees do. Then they wouldn't look much like daisies, they'd look like trees.
You can worry about all that for your story. Or you can just decide it's cool and hang a lantern on it like Atomic Robo does with equally implausible giant insects.

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give italic and italic. The question is what makes the woody Dahlia a Dahlia and not, for example, a *Dahlioïdes or a *Paradahlia? That is, I would have no problem with a tall tree bearing flowers sort-of similar to dahlias, but it just doesn't feel right to say that that the tree is actually a dahlia -- how could it be, since it shares nothing with our dahlias? Or is it just an extraordinary coincidence that the aliens use the word "dahlia" for "eucalyptus"? $\endgroup$ – AlexP Jul 11 '18 at 17:52