Winter burial for fig tree in zone 5

We take our mentors' lessons in the Minnesota Tip to bring a tender tree through the winter.

Just dig a pit and bury it. It'll be fine!

Ah, the common fig, Ficus carica. Gardeners so love this fruit that they jump through hoops to grow it in their own garden, even though the region is too cold to support a blooming, fruiting fig.


Although a fig's roots will weather winter in USDA hardiness zone 6 or a sheltered place in zone 5, the top of the tree won't survive in air colder than about 15° F. Since it's the top of the tree that must remain alive from year to year in order to produce fruit, a fig's only reliable in the landscape when grown in zone 8 and 9. One way around the cold winter is to grow the tree in a pot and move it into a no-freeze building late each fall. Another method is what we're doing here -- using a "Minnesota Tip" to bury the tree as killing frosts begin in late fall.

The Minnesota Tip method can be applied to many plants to buy a zone or two of protection from winter cold: To tree-form roses to protect the top graft, to blue hydrangeas, crape myrtles in cold zones... Here we tip a fig tree to handle a zone 5 winter.

The Minnesota Tip method can be applied to many plants to buy a zone or two of protection from winter cold: To tree-form roses to protect the top graft, to blue hydrangeas, crape myrtles in cold zones... Here we tip a fig tree to handle a zone 5 winter.

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 Timing
 Digging the pit
 Tying the tree
 Cutting roots on one side
 Tip the tree
 Wrap it
 Burial
• Apply to other plants!

Timing

We pluck the leaves off the tree
  since they will not serve any
  purpose underground and will
  only drop off when we unearth
  the tree in spring.

  Ideally, we'd wait to tip the tree
  after the cold made the foliage
  drop. However, work in our
  volunteer garden at the Detroit
  Zoo is subject to the universal
  imperative, that the best time
  to do a thing is when we can.

Sure, there's a 'best time' for everything, but the time to do a thing in the garden is when you think of it.

Digging the pit

We've dug a pit from one side of the trunk about a foot deep, two feet wide and as long as the tree is tall. (Below, right: Paul in the orange cap is standing in the pit.) The width is a guess, our estimate of how wide the tree will be once we tie its branches. In four of the five years this tree's been in our Detroit Zoo garden, we unearthed the tree entirely and buried it where we had a perennial-free space. This year we knew it would reach a size we'd rather tip than lift, so we planted only annuals to one side of it.

Tie the tree to make it small

We press side branches together against their main branch and use string or rope to hold them in that bundle. Then we pull the bundled main branches to the trunk. The best ties are wide and soft to avoid cutting into the bark.

Above, left: Janet's holding a group of branches to its trunk while Gordon ties. Phil in the red jacket is pulling all the main branch bundles together. If you don't have extra hands to accomplish this feat, use elastic bungee cords to cinch the branches in a series of ever-tighter bundles.

Why tie? We don't want to dig a pit as wide as this tree! Also, bundled branches are stronger than individual twigs -- see "Wrapping" for why we care about twigs.

Cut loose one side of the root mass

The tree's tied. The pit's dug. Now we excavate around the far side of the trunk, cutting through the roots about two feet out from the trunk. We undercut the root mass on that side of the tree and also remove soil from the root ball to lighten it.

  (Is this a man's job?
  No, this crew came to
  be this way simply by
  serendipity. Janet's a part,
  but is also the one to step
  out of the frame to say,
  "Wait, let's get another
  picture." Phil Gigliotti is
  in charge of this part of
  our team's garden and
  as experienced at wintering
  tender trees as Janet, having
  overwintered figs in his home
  garden for decades.
  Paul Needle jumped in as the
  first person to arrive to find
  Janet digging the pit.
  Gordon Findlay stepped up
  when we called for, "Someone
  tall to come take off the
  top leaves.")

Tip the tree

Now we tip the tree into the pit. In-ground, the tree's wood will only be as cold as frozen ground, 32F. That's much warmer than zone 5 air, which may drop to -20F.

Wrap the package

We wrap a tarp around the tree to prevent damage when we retrieve it in spring. We want to avoid breaking the branch tips as we dig. The tips must remain intact -- they are what is ready to bloom and fruit. We had two crops from this tree this year, which is common. The overwintered shoots bear first, then newer shoots. (Usually the second crop is most tasty but we can't vouch for that as we lost most of the fruit to squirrels. You will note that we are not daunted. Another thing our mentors taught us is to always look forward to next year.)

 

Burial

Then we bury the tree. We mound up over the tipped half of the root ball. In this case, that took four wheelbarrows of soil and rotted mulch stripped from our garden paths. We topped off the mound with insulating straw. This was not essential but we had all that "perennial straw" on hand -- cut down ornamental grasses, tall annuals, etc.

Applies to other tender perennials, shrubs and trees

We've showed you this process with a rose tree and explained that you can also bury cannas, dahlias and other tender perennials to take advantage of ground warmth. We've explained how to achieve this protection for hydrangeas that are only root-hardy, not branch hardy in zone 5. (blue- and pink-blooming hydrangeas, Hydrangea macrophylla varieties such as 'Nikko Blue', H. serrata and its hybrids). Check out burying and other methods in What's Coming Up issue 7 for tender perennial tactics, or Wondrous Root Cellars and Growing Concerns 591 for just about anything.

There are even more articles about winter protection here at GardenAtoZ. Use our Search function to search key words such as "winter (your plant name)"

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