Ask Mr. Smarty Plants

First. we need to determine if the plants you are asking about are native. The Lady Bird Johnson Wildflower Center recommends only plants native not only to North America but to the area in which they are to be grown; in your case, Comanche County, OK.

Missouri Botanical Garden Sargent Crabapple - native range Japan. There are five members of the Malus (crabapple) genus native to North America, only Malus ioensis (Prairie crabapple) is native to Oklahoma, but this USDA Plant Profile Map does not show it native to southwestern Oklahoma. There are are 16 members of the genus Viburnum native to North America with the name "arrowwood" in the common name; of these, 3 are native to Oklahoma, but none really grow close to southeast Oklahoma. There are several other viburnums not native to North America at all, so we don't know which one you have. Crataegus phaenopyrum (Washington hawthorn) is native to North America but not to Oklahoma.

The point of all this is that we are going to give you some websites on which you can search for plants poisonous to dogs and horses, but it is much easier to search on them using the scientific names, as in Malus ioensis (Prairie crabapple).

The lists often are only plants native to North America, but ordinarily if you search on one genus name (malus, viburnum or crataegus) the information on the poisonous plants will be the same for all species of that genus. Here is our list:

ASPCA

University of Arkansas

University of Illinois   

Toxic Plants of Texas 

Poisonous Plants of North Carolina

University of Pennsylvania Poisonous Plants

Canadian Poisonous Plants Information System 

California Poison Action Line 

You should also check with your veterinarian to make sure some locally available plant has not been proved to be poisonous that is not on any of the lists.