Watering trees, growing biennials and a great garden tour

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June 17, 2014
By: Meleah Maynard
Meleah Maynard

Until I became a gardener, I never realized how little rain actually reaches the ground beneath mature trees. When it rains, you figure that the ground is wet so you don’t need to water, right? Wrong. Even after a soaker that dumps 2 inches or more of rain, I’ve found that the soil around the base of a tree can be very dry because the bulk of the rainwater can’t get past all of those branches and leaves.

To keep trees healthy, you need to water them yourself and the general recommendation is about an inch of water per week. That’s not easy to estimate, so let me offer some more concrete ideas. For newly planted trees, fill a 5-gallon bucket with water and slowly pour it over the root area every three or 4 days from planting time until the ground freezes. For mature trees, it’s best to water until the top 6 to 8 inches of soil beneath the canopy is wet.

Soaker hoses are great for this purpose, but you can also use a regular hose on a slow trickle or a sprinkler on a low setting. You’ll just have to move the latter two options a few times over the course of three or four hours, depending on the size of the tree. To check the moisture level, use a tiling probe, which most garden centers carry, or a simple iron rod. You’ll be able to see whether the soil is wet or not after poking around for just a few minutes. It may be raining now, but if this summer goes like the last two or three, we’ll be dry and droughty soon and your trees are going to need you.   

Growing biennials 

Everyone’s always talking about perennials and annuals, but you don’t hear a lot about biennials. Maybe that’s because they complete their entire lifecycle in two growing seasons. That means that they live and die as follows: first year: leaves; second year: flower stalk, blooms and seeds; third year: dead. Run away! You say. I hear you, and I have lost many biennials that I’ve tried to grow over the years. But I’ve vowed to try to grow them again using a fairly easy-to-follow strategy that ensure your biennials behave more like perennials and come back from year to year.

No, I’m not a glutton for disappoint. Honesty, I just love delphiniums, Korean angelica, foxglove, Iceland poppies, sweet William and Forget-Me-Nots, and I’d like to keep them going in my gardens. I figure some of you might like to do the same, so here is what we’re going to do. For the first year, choose a few hardy biennials you like and either sow seeds or plant seedlings.

Once the plants have made it to the spring of their second year, sow more seeds or plant more seedlings near the first ones you planted. Soon, your second-year plants will be in bloom while the foliage on your first-year plants is getting started. In the fall, your second-year plants will go to seed, relieving you of reseeding duty. When spring comes, you will again have second-year plants blooming while newly seeded plants and growing their first flush of foliage. I’m on my second year with blue delphiniums in my garden, so wish me luck and I wish you luck too.

Garden tour in Northeast, Southeast and Longfellow 

It’s hard to believe because summer has been slow to start, but the Hennepin County Master Gardener Learning Garden Tour is just around the corner on Saturday, July 12. This year’s tour features eight gardens in the Northeast, Southeast and Longfellow neighborhoods of Minneapolis.

Learn more about the tour and purchase advance tickets for $15 here: hennepinmastergardeners.org/events/hcmg-learning-garden-tour/. Or you can buy tickets the day of the tour for $20 at any of the gardens, which will be listed on the website above the day of the tour. Master gardeners will be on hand to answer your gardening questions, and there will be lots of educational demonstrations too.

Get more gardening tips at Meleah’s blog: www.everydaygardener.com