Identify a somewhat rare tree in North Dakota

A: The tree is the northern catalpa. It is somewhat rare in North Dakota, compared to other more common trees like ash, elm, oak, maple, and linden. There is a very large specimen in Wahpeton, North Dakota that holds the state record at 54 feet in height.

Northern catalpa attracts attention, both during flowering and when the long pods are developing. Blooming in June, the showy white bell-shaped flowers are accented with purple and yellow and ruffles around the edges.

The pods are quite spectacular as they hang down from the tree, each reaching a length of 8 to 20 inches and filled with papery seeds. The huge leaves are on average 6 to 12 inches long.

The northern catalpa, whose botanical name is Catalpa speciosa, is generally considered winter hardy up to Zone 4. It is better suited to sites south of Interstate 94 than to areas to the north.

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Catalpa makes a beautiful specimen type tree where you would like to showcase something unique. They are best planted in protected microclimates within established neighborhoods. Open and windswept sites often lead to dieback and freezing.


Question: Do ornamental grasses have to be cut every year or can they be left alone? – Duane N.

A: For optimal health, it is best to cut ornamental grasses just above ground level once a year. New growth emerges from the ground each spring, and if the old, dried tops are not removed each year, a tangled mess would soon build up and, over time, the health of the grass would deteriorate. Prairie fires have often accomplished this cleansing in nature.

There are two options for annual cutting of ornamental grasses. Because aerial stems and seed heads are often quite ornamental, they add beauty to the winter landscape if left untouched over the winter. Cut close to ground level in the spring before new shoots appear.

Alternatively, ornamental grasses can be cut back in the fall after several severe frosts. If your springs are choppy and you’re worried that you won’t get the job done before new growth begins, it’s best to cut back in the fall.


Question: I planted a new hydrangea shrub in our landscape this year and it produced some beautiful deep pink flowers! How to keep it alive during the winter? – Kayla C.

A: Do you know what is the name of hydrangea? Types of hydrangeas vary widely in their adaptability. Several types are well suited to most areas of the Upper Midwest, while others struggle. Many of the dark pink flowering cultivars are more closely related to the flower hydrangea and are not as winter hardy as the adapted cultivars. The first step is to check the plant label for the exact hydrangea species and cultivar name.

For types that are at the limit of adaptability, like the Endless Summer series, a winter mulch applied from early to mid-November is a good safeguard. Covering the plant with about 12-24 inches of leaves, straw, or chipped wood helps protect the plant, with the mulch being removed the next spring before growth begins.

If you choose chipped wood, after fulfilling its function as a winter protection mound, the mulch can be removed and left in a layer around the hydrangea during the summer. Hydrangeas love moisture, and mulch keeps the soil moist and cool.

If you have a gardening or lawn care question, email Don Kinzler, NDSU Extension-Cass County, at [email protected] Matters of high interest may be posted, so please include your name, city, and state for appropriate guidance.

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