Whitethorne LLC: How This Women-Led Business Is Creating Opportunities for Others   

Georgy Maskrey-Segesman, Mavis Spencer, and Con Calle

By Tyler Bui

In this sport, education and opportunity are invaluable—and Whitethorne LLC strives to contribute their share of each for the industry. 

Led by Georgy Maskrey-Segesman, Whitethorne LLC develops top Grand Prix and jumper mounts, provides rehabilitation and wellness care for horses, and works to promote growth and development within the sport. With big goals in mind, Maskrey-Segesman, along with her team of professionals and riders, sets an exemplary example for the industry. 

Whitethorne, Maskrey-Segesman’s childhood home in England, sat right next to a stable that bred horses. Her bedroom window overlooked the pasture with the mares and foals. And so, from a very young age, she knew horses were going to be a part of her life. When she turned 10, Maskrey-Segesman and her family moved to the US, where she continued to ride and develop her relationship with the sport. 

“I just couldn’t imagine my life without horses. I couldn’t imagine having a regular job and not being around horses all day,” she tells The Plaid Horse. 

During her junior years, she began riding with Tom Blakiston, eventually taking on a role as a working student and an employee. After completing her degree in business administration, Maskrey-Segesman developed a plan to attend law school, which prompted her family to look into purchasing a farm to stable her horses while she completed her studies. 

In 2001, the property in Somis, CA, was purchased and named after her childhood home. The original plan to buy a small farm was replaced with a 22-acre, 76-stall property, and Maskrey-Segesman made the final decision to pursue her career as a professional and devote 100 percent of herself to Whitethorne and the sport.

With such a large property to care for, the first step was to fill stalls to get Whitethorne up and running. Julia Balcom was the first to take her business to Whitethorne, bringing her string of over 20 horses to the farm. The two merged their businesses about 10 years after Balcom’s move to Whitethorne, and they worked together for 17 years. 

“In the beginning, I took anything that came in off the road. It didn’t matter what it was. I had a Paint Percheron who jumped around in the 80 centimeters, and I had off-track Thoroughbreds,” says Maskrey-Segesman. “Whitethorne became a laboratory of education because we had so many different horses, horses that you can make really great in their own rights.”

In 2014, Karen Healey moved her business to Whitethorne, cementing a pivotal moment in Maskrey-Segesman’s career. 

“I sat on the fence, I paid attention, and listened and learned. I would say that was the turning point for my business into the equitation sport,” she says. “Sitting there and learning how to do the sport classically from Karen was really important. I found that I really enjoyed the equitation, I really saw where you could build a solid foundation out of the equitation and then I decided I would put my own twist on it. I very much subscribe to the forward style of riding.”

During a visit to Germany, Maskrey-Segesman met her current partner, Tjeert Rijkens, right around the same time she established Whitethorne LLC, but the two did not begin doing business together until about eight years later, when she shifted her business to be more sales-focused and less on clients. Today, Whitethorne LLC focuses primarily on sales and their show jumping team, in addition to Maskrey-Segesman’s ventures to provide opportunities and promote education. 


Maskrey-Segesman leading Spencer and Ekarlus

The Whitethorne LLC Show Jumping Team 

In February 2020, Maskrey-Segesman found herself without a rider. In addition to finding a rider with talent, she was looking for a well-rounded, true horseman. Mavis Spencer caught her eye. At the time, Spencer was working in the horse industry but was not competing. 

“I sat down and I talked to her and I said, ‘It’s my greatest dream to go to the top of the sport in show jumping as a coach and as an owner.’ I think she looked at me like I had three heads, wondering if this could actually be true. We’ve been slowly developing a string of really great horses along with a delicate balance of selling horses to make sure that we can maintain the momentum.”

Some of Spencer’s current mounts include 9-year-old Carissimo 25, better known as “Curly,” who recently took home fifth in the $138,000 CSI3* Grand Prix 1.50 m and third in the $37,000 CSI3* Welcome Stake 1.45 m at The Great Lakes Equestrian Festival (GLEF). At the Kentucky Spring Classic, Curly and Spencer rode to second place in the Commonwealth Grand Prix. He has also placed in eight of his last nine international starts with  Spencer. 

Con Calle is a 13-year-old bred by Rijkens. Spencer rode the gelding to two second place finishes at the Devon Horse Show in the $37,000 CSI4* Main Line Challenge 1.45 m and the $37,000 CSI4* Devon Speed Derby 1.45 m. Most recently, at the Great Lakes Equestrian Festival, he placed fourth in the $37,000 CSI2* Welcome Stake 1.45 m, fifth in the $37,000 CSI2* Two Phase 1.45 m, and sixth in the $37,000 CSI2* Speed Classic 1.45 m.

Contonio, half brother to Con Calle, is another horse bred by Rijkens. Ekarlus is a horse owned by Ken Dickey who has been brought along to the 5* level, and then there’s the up-and-coming 6-year-old mare Contra. Working together, the two women have big goals to accomplish.

“Georgy is one of the most genuine people I have met in this industry,” says Spencer. “She cares deeply about the horses and people around her and is constantly striving to create opportunities for all of us. It is really refreshing to see that and be a part of it. It feels more like a big family at Whitethorne. Her love of the sport and creating opportunities is not just limited to us though. She is constantly looking for ways to make the sport more accessible and doesn’t just talk about it—she really puts her ideas into action and there is a lot to be said for that. I have so much to be grateful to her for and have so much respect for her as a horsewoman, partner, mother, and true friend.”

“I would very much love for Mavis to be able to go to the Olympics. I think we’re hopefully well on our way,” says Maskrey-Segesman. “Patience and listening is my philosophy when it comes to horses. They tell you what they want to do, they tell you what they don’t want to do. They don’t have to fit into our box, we have to fit into theirs. I think that’s the biggest thing.”

Alongside Maskrey-Segesman and Spencer are Whitethorne’s professionals Chelsea James, Killian McGrath, and Ivey Burns. 

“Everybody has their own specific sphere that they operate in and they do a great job,” says Maskrey-Segesman. “Killian was my original rider at Whitethorne, we did the Longines Masters in Los Angeles, she went to Spruce Meadows and jumped the 1.50-meter on one of my horses. Now, she’s teaching, riding, and keeping everything going. Ivey helps out at the horse shows occasionally as well, and Chelsea travels to horse shows and also trains as well.”

Caring for More Than Just Her Own  

Working as its own separate entity is Whitethorne’s rehabilitation program. While it was not originally part of the overall plan, the program has developed into a top-notch facility fitted with the most innovative technology for the highest quality care. 

“I originally bought these pieces of equipment for my horses, starting with a saltwater spa and the Horse Gym Treadmill,” Maskrey-Segesman says. “I realized I had a 14-stall barn that I was not doing anything with, so I decided to build an in-ground aqua treadmill and turn the barn into a rehabilitation scenario. My idea has always been trying to make things affordable and doable for most. That doesn’t mean compromising quality, but that it should be accessible to everybody. For the health and welfare of the horse.” 

Not only is Whitethorne’s rehabilitation there for horses recovering from injury, it also offers a great place for show horses to rest and recover after show season. Whether it’s being turned out in a grass pasture, using the saltwater spa, or keeping up fitness on the aqua treadmill, the program offers a program for any type of horse. 


Horses stabled at Whitethorne LLC

Creating Opportunity 

After years of experience in the sport and also running her own business, Maskrey-Segesman knew there was more she could do to make an impact in the industry. Today, Whitethorne offers both the Whitethorne Equitation Challenge and the Whitethorne/Elvenstar Equitation Tournament, two opportunities for riders to grow in both their education and riding skills. 

“I have always wondered why there isn’t more transparency in the sport of equitation. I thought it would be so beneficial to have some feedback,” she says. 

The Whitethorne Equitation Challenge pairs a top trainer outside of the California area with a judge who often is judging a national championship that year. The two will sit with scribes while judging the class, and after, riders participate in a meeting where they are able to ask the judges questions. A sports psychologist is brought in to talk to the riders, and a short film is usually shown. 

“The interesting thing about the class is that riders tend to grow. They tend to improve upon their scores, they tend to learn something, and they really enjoy it,” Maskrey-Segesman says. “The trainer wins a cash prize, the rider wins a saddle, and it just ends up being something different but all for education, growth, and learning.”

The Whitethorne/Elvenstar Equitation Tournament is run in conjunction with Elvenstar and West Palms Management. It’s similar to the USET final with a flat phase, gymnastics phase, show jumping phase, and a final phase where the top four riders trade horses. The class is open to juniors and professionals and offers a $20,000 prize. 

“I wanted to do something that gets people excited about the equitation, but mainly something that is beneficial for the sport,” she adds.

In addition to the Whitethorne Equitation Challenge and the Whitethorne/Elvenstar Equitation Tournament, Maskrey-Segesman makes an impact as she personally sponsors a select group of riders. 

“I do very much believe in giving back.Trying to help people who are in need. I sponsored Emma Pacyna for her last two junior years, and one of my fondest memories was going on that journey with Emma. For her and I both, getting a ribbon at national level was a massive success. It was something that was so incredibly rewarding.”

“I feel like there aren’t enough opportunities out there, and I feel very strongly that if we’re able, we should give opportunities to kids who need a little bit of help,” she says. “I just want to be able to have a positive impact on the horse community. I think that is the most important thing.” 

Learn more at whitethorne-llc.com.


Photos © Sara Shier Photography & Bethany Unwin Photography

*This story was originally published in the September 2022 issue of The Plaid Horse. Click here to read it now and subscribe for issues delivered straight to your door!

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