Ambrosia Maple is not a species of maple, rather it is a term that describes a distinctive figure common to soft maples produced by a beetle and a fungus. On infected wood, you will see small holes typically 1 mm in diameter. Surrounding the holes are greyish wisps of fungal stain that resemble puffs of smoke or flames. These puffs travel away from the hole up and down in a vertical direction. The overall look is unique; some woodworkers will like it, others may not.
The name comes from the Ambrosia beetle, which is a member of the Weevil group. Females bore holes straight into the tree. The beetles have unique structures on their bodies which hold the fungus. As the beetles excavate the galleries, fungal spores infect the wood and grow on the walls of the galleries and in the surrounding wood. The fungi are carried away from the holes by the action of the trees sap.
The female beetle then lays eggs in the excavated galleries. When the larva hatch, they consume the fungus growing in the galleries. The beetles are creating fungal farms which benefit both the insect and the fungus. After pupating, newly emerged adults will leave the infected tree to search for new host trees to infect and the cycle begins anew.
Unlike other insect pests, Ambrosia beetles don’t eat the wood of an infected tree. The uneaten wood or frass is pushed out of the tree and collects on the ground. Ambrosia beetles typically prefer dead or stressed trees. They also like saw logs and green lumber. The fungus also does not consume the wood. The staining is purely cosmetic, and the wood of the Ambrosia maple is structurally sound.
Ambrosia Maple was considered a defect and for years was sold as an inexpensive wood for making frames of upholstered furniture. Today, woodworkers appreciate its unique appearance and demand for Ambrosia Maple has increased along with the price. Supply is limited, so I would call a reputable specialty lumber dealer for availability.
Most woodworkers will encounter the Ambrosia figure in Red Maple and I will use it as the type species for further discussion. Red Maple with the Ambrosia figure will plane and machine the same as Red Maple. If you are working with Ambrosia Maple that also has figure, you may experience tear out. Keep your tools sharp and watch your cutting speed and feed rates. Nails and screws will need to be predrilled. Gluing shouldn’t present problems as long as you monitor clamp pressure to avoid glue squeezing out and causing starved joints.
Finishing Ambrosia Maple is where the fun begins since you will want to highlight the Ambrosia figure. I wouldn’t recommend staining since it will blotch and obscure the figure. Oil based finishes are your best choice as they will accentuate the fungal tracks. Solvent based lacquers can yellow so a water-based formulation may be better if you prefer a film finish. It’s up to you whether you want to fill the insect holes.
Ambrosia Maple has long been a favourite of turners. The distinctive look adds interest to bowls, platters and spindle turnings. Large slabs of Ambrosia Maple are used for table and desktops. It can be milled into an interesting flooring and furniture makers use it for panels and drawer fronts. Adventurous luthiers are incorporating it into solid body guitar tops and acoustic guitar backs and sides. Ambrosia Maple is also sliced into decorative veneers.
At the sawmill, Ambrosia maple is separated from other maples and accumulated. When it arrives at the lumber dealer, it will probably be a mixture of different maple species and also from different trees. Take your time when selecting boards, paying attention to background colour and figure density. Effort at this point will help create a unified visual appearance for your project.
Insects have coevolved with trees, and they influence the forests we rely on in both positive and negative ways. The story behind the Ambrosia Maple is not just about an interesting figure. Ambrosia Maple also reminds us of the complexity of our forests and how tree, insect and fungus have combined to produce this unique wood.