Ornamental grasses have recently become one of the more popular "alternative" plants for use in the landscape.   Although their use is increasing, they are still underused and underappreciated.  With only basic care, ornamental grasses can be some of the most rewarding plants in your garden.

 

 

Ornamental grasses begin cropping up in garden centers in the spring.  Because most grasses that are popular in our area are "warm season" grasses (meaning they grow best when temperatures warm in spring), they begin to look their best in mid-May to early June. 

 

For best results plant ornamental grasses in the spring to early summer.  Although many say that grasses can be planted at any time of year, we have found with experience that late planting (fall planting after August) is NOT very successful.  Planting this late does not allow the plant to root in before winter, and quite possibly the dense rootball characteristic of the grass plant is not secured in the ground and susceptible to frost heave (being pushed up out of the ground by freezing and thawing).

 

 

Ornamental grasses come in a variety of sizes and shapes.  Most are clump formers and will reach a fairly specific height and width.  Be sure to read labels carefully and consider the ultimate size of the plants.  Some, such as Maiden Grass, can easily reach 6 feet across and 8 feet tall.  Don't worry - there are other varieties available that stay at a more managable 2 or 3 feet tall and wide (like Dwarf Fountain Grass) if ultimate size is a problem.

 

Most ornamental grasses like sun.  That means, for best results, they should receive at least 6 to 8 hours of direct sunlight per day.  With less sunlight, the grasses will likely still grow.  However, they will be less vigorous, more likely to collapse, and less likely to bloom (the feathery plumes that are the flowers of grasses).

 

A few of the taller grasses that will tolerate shade are switchgrass (Panicum virgatum) and feather reed grass (Calamagrostis spp.).  Sedges, although not true grasses, are low-growing grass-like plants that actually love the shade.  Try 'Ice Dance' or 'Evergold' for your shady garden.

 

 

Most grasses that are used in the landscape are clump formers.  For the most part they stay put where they are planted.  They do not tend to self-sow seed and become a nuisance in this way.  One notable (but still lovely) exception is Northern Sea Oats (Chasmathium latifolium).  It has beautiful, pendulous oat-like flowers that dangle like earrings.  Once planted however, you will have a barrage of seedlings springing up all over its general vicinity.  Combat this problem by using a pre-emergent herbicide religously in the spring.

 

There are a few grasses that will spread like wildfire in the garden.  Beware of planting these specimens, as they will likely take over your garden and will even try to colonize your lawn:  Blue Lyme Grass (Elymus arenarius 'Glaucus') and Ribbon Grass (Phalaris arundinacea).

 

 

One initial word of caution:  some grasses have sharp foliage that can cut you just like a papercut (especially Maiden Grass and its relatives).  When working with grasses, gloves are a wise accessory to use.

 

In general, follow the instructions on our Planting Tips: Annuals, Perennials and Groundcovers page.  Because grasses tend to have extremely dense rootballs, be sure to slice or "score" the rootball by using a knife to make several vertical cuts on the exposed rootball after taking the plant out of the pot.  It is also important to make sure the grass is planted at the correct level - soil level of the potted plant should be equal with the surrounding soil once the plant is in the hole.  Grasses planted too shallow (or slightly sticking up out of the ground) are more likely to frost heave in the winter and are more susceptible to winter injury.

 

 

We are frequently asked regarding the right time to cut back ornamental grasses.  We like to cut them back in mid-March, before new growth starts but after you have enjoyed them for the winter.  You may also trim them back in the fall, but you will not be able to enjoy their beauty in the wintertime.  Some people cut back their grasses in the winter after a few heavy snowfalls have smashed the clumps down.

 

Do not wait too late in the spring to cut back your grasses.  New growth will try to emerge and be subdued by the abundance of last year's dead grass.

 

Cut back grasses as close to the ground as possible (usually down to 3-6").  When the grasses are young, a pair of bypass pruners should suffice.  As the clumps age and become bigger, you may need to use electric hedge trimmers.  BE CAREFUL when cutting back grasses as well - the straw that grasses become after winter can be sharp and hazardous, especially to the eyes.

 

 

Yes, it happens.  Clump forming grasses are so vigorous that as they age, the middle of the clump begins to die out and new growth is produced only by the edges of the plant, forming a specimen that looks a bit like a donut when viewed from above.

 

To prevent this phenomenon from happening, regularly divide your clump in the spring.  Do so by lifting the clump, separating the healthy parts of the grass, discarding the dead sections, and replanting the divisions.  (You may use this opportunity to plant parts of your grass in other areas of the garden, or pass a division or two on to your neighbors).