http://www.springer.com/life+sciences/plant+sciences/journal/40529

Also,

Several countries / institutions have an agreement with Springer, to publish with lowered/no costs. http://www.springer.com/life+sciences?SGWID=0-10027-0-0-0 

http://www.journals.elsevier.com/scientia-horticulturae/

http://www.agriculturejournals.cz/web/HORTSCI.htm

http://www.fruits-journal.org/

http://link.springer.com/journal/10681

http://journal.ashspublications.org/

http://www.eigenfactor.org/openaccess/index.php?catid=14&pt=0

Scroll down to "No-fee Open Access Journals ordered by AI for PLANT BIOLOGY"

Also,

http://www.as-botanicalstudies.com/

It is a new open access and free publishing journal..

http://www.biotechnologicalresearch-journal.com/

Useful link for your question : http://ijaridea.com/Knowledge-Empowerment

Journal of Horticulture and Postharvest Research

http://www.jhpr.birjand.ac.ir

Any Journal for Floriculture? especially on productivity and economic analysis?

www.jhpr. birjand.ac.ir

journal of ornamental plants

Journal of Horticulture and Postharvest Research (JHPR)

Journal of the Science of Food and Agriculture

Journal of Food Science and Technology