Elm trees are of the genus Ulmus. I don't know anything about kids, this may be a stretch.

Uvularia. I believe the common name is merry bells.
It scares me that this immediately came to mind when I saw the subject of your post. Too much time reading my garden books!

Hi;-
I do not recall that many plants beginning with the letter *U* but here are a few;-

Ugni [Chilean Guava] ;- A beautiful evergreen shrub .
Ulex [Gorse] ;- An unusual, almost leafless, fragrant flowers shrub.
Umbellularia [Headache tree] ;- It is said that the aromatic leaves are used as an insect repellent.
Urceolina ;- Not sure of the common name. A genus of spring flowering bulbs.
Urginea [Hook sedge] ;- Another flowering bulb that flowers in late summer.
Ursinia [Star of the veld] ;- A genus of perennials and annuals, some for foliage others for flowers.
Utricularia [Bladderwort] ;- Carnivorous water plants.
Uebelmannia [Cacti] ;- I think this unique genus is from Basil.
Uncarina [Succulent] ;- Trees and shrubs with beautiful flowers and fuzzy leaves.

Supannee
Ankrara's Hobby Corner

Thanks for the post, I am kindergarten teacher and we just completed our ABC garden and I could not find a "U" plant for our zone.

Umbrella Palm. It is a water plant but could be grown in a pot if it is kept moist. You might try it. Look for it at a water garden center or sometimes Lowe's has it.
Good Luck,
Karen

Uva-ursi (Arctostaphylos uva-ursi) AKA kinnikinnik - native evergreen groundcover with pink flowers and bright red berries. Not poisonous. Hardy.

Umbellularia californica - California bay laurel/Oregon myrtle - native evergreen tree with aromatic and edible leaves. Can be used as a substitute for bay leaves (but the taste is much stronger) Zones 8 and up.

Umbrella pine (Sciadopitys verticillata) - conifer that is native to Japan, slow grower, hardy.

Umbrella plant (Cyperus alternifolius) - related to papyrus, the plant the Egyptians used to make paper. Water sedge, 2-4 feet, self sows and may be weedy, tender.

Umbrella magnolia (Magnolia tripetala) - deciduous tree to 40 feet high, hardy. Doesn't bloom until 10 years old, but has 10 inch wide white flowers in summer.

Umbrella tree/octopus tree (Schefflera actinophylla) - Evergreen shrub, tropical, usually a houseplant.

Urbinia agavoides (AKA Echeveria agavoides) - Succulents, tender, looks like hens-and-chicks.

BTW, Gorse (Ulex) catches on fire very easily, has many large thorns, and is poisonous. It is a listed noxious weed in Washington, Oregon, California, and Hawaii, and should not be planted in the arid SW, where it would be a fire danger. Check with your local government before you plant this.

I believe there is a fruit called "Ugli" fruit. I have no idea what the plant name is, though.

I have something in my garden right now called a unicorn plant aka devil's claw. A word of warning though, mine have gotten so big I have had to chop off large sections. Plus the leaves are sticky, almost like flypaper. I grew this with my tomatoes because I was told it would attract tomato horn worms to it rather than my tomatoes. I don't think this will be a repeater for me next year though.

Ugli fruit is a registered trade name for cross between a mandarin orange and a pomelo.

Uncinia uncinata (Red New Zealand Hook Sedge)