Harvest of murder / Ann Ripley.

Enhanced descriptions from Syndetics:

"Harvest of Murder" is the sixth book -- and Ripley's debut on the Kensington list -- in her delightful series combining mystery with useful gardening tips. This time out, Louise Eldridge, wife, mother, and television gardening show host, finds herself caught up in the chaos of a holiday feast, a new high-tech job.. .and a brutal murder in her own backyard.

As Thanksgiving draws near, Louise has her hands full. Her daughter is demanding her attention, her husband wants her affection, and her gig as a holiday hostess is shaping up to be one stressful act. To escape the madness, Louise has been sharing nightly dog-walks with Dr. Peter Whiting, an eccentric old biologist who regales her with tales of his travels in the Amazon jungle and his incredible discoveries there -- including an exotic formula that can double a person's life expectancy. But Louise is shocked when the good doctor is found slashed to death in the woods near her home.

Only a week later, Louise gets an invitation from Whiting's widow to help complete the plant experiments that had been her late husband's obsession. But even as she accepts the offer, Louise can't shake the feeling she's getting up to her elbows in something more sinister than seeds and soil. For there's a lot more going on at the lab than simple science, with intrigue involving billions of dollars and a rogue's gallery of suspects. Little by little, Louise is digging up dangerous dirt on all of them. But if she's not careful, this Thanksgiving could be her last!