By Susan Leigh Anthony, Kennedy’s Perennial Buyer
Cool days are great days to work in the yard. Over the last few days, I have been occupied with picking up at least a million tiny twigs from every inch of my property. The good thing about this is that it’s given me an opportunity to see what’s coming up in my garden and make a mental “to do” list of what needs attention.
Here are a few important tasks to take care of in April:
Cutting Back Ornamental Grasses
Note that the ideal time to cut back ornamental grasses is late winter to early spring, but as long as you don’t cut into too much of the fresh new growth, it’s fine to do it now. Cut back, leaving only a few inches of old growth. For taller grasses, it is wise to wrap heavy twine or tape around them, so the blades stay together and don’t cascade all over the place. Sedges and blue fescue grasses can use freshening up, so cut the fescue back to a few inches and cut sedges down by about a third.
Pruning Lavender (Lavandula)
Let me start by saying I have read a lot of varied information on how and when to prune lavender, but this is my method and it works well for me. In early spring, cut back about 1/3 of the foliage. Keep the plant as rounded as possible and you will be doing it the way they do in Provence! Larger varieties, such as Grosso and Provence, can be pruned back about half way. If you have an old, very woody plant, you can help it out by pruning down a bit harder, to about 3 nodes above the beginning of the woody part. Sometimes it is just best to kindly say “goodbye and thank you for your service” to lavender plants and bring in new ones. To keep in mind for later in the year: After the first blossoms in mid-summer are past, prune down into the foliage by about a half inch; you will be rewarded by a second, somewhat lighter, bloom.
Pruning Russian Sage (Perovskia)
Many varieties are available now in a range of heights and habits. All can be treated the same as far as pruning. I actually prune mine part way in the fall after a hard frost. Remove dead twigs and broken or damaged branches, leaving a balanced framework of stems. This will stimulate strong growth and flowers the following summer. In the early spring, cut back all growth from the past season to healthy buds, down to 6-8 inches from the soil. Remove any dead branches as well as broken or damaged wood. Remove any skinny twigs incapable of supporting strong new branches next season. If possible, cut back a few of the oldest stems close to the soil, to encourage strong young shoots to replace the older ones.
Pruning Montauk Daisies (Nipponanthemum nipponicum)
If you are one of the many folks who love your giant, very late blooming, Montauk daisies, here are some tips to prevent floppy plants. In early spring, remove any dead stems or roots. If the overall stem arrangement is thick or crowded, thin the Montauk Daisy by cutting some of the stems to the base of the plant to create more space between the stems that will allow air to flow through the plant. For a strong fall bloom, prune plants to about 8-10 inches tall in early spring, with a second strong pruning by early July. I have seen some of these plants grow to the size of a large shrubs, making them seem ungainly and clunky. They can certainly benefit from occasional division, and spring is an excellent time for that, too.
Dividing Other Perennials & Grasses
Speaking of dividing perennials, most perennials are fine to divide in the spring. April into early May is the best time. After that, transplanting is iffy due to the warmer weather and less rain. Division under less than the best circumstances can really stress the plants. I find the best method is to dig up the entire plant and carefully cut through the root clump with a large sharp knife or sharp garden spade. A small garden saw can also work. Others have reported use of a power tool such as a reciprocating saw using an old blade you don’ care about. The size of the root clump depends on how big you want the plant to be or how many you plants you want.
Any time you divide and transplant the plant gets a little shocked, so try to do it when the sun is not too strong. An overcast day, early in the day, or late in the day. I like to water the plant prior to moving it. Keep the plant well-watered once it is moved and be patient if it looks a little wimpy at first. Here is a short list of plants that should NOT be divided in the spring: Peonies, Oriental Poppies, and Bearded Iris. Generally spring blooming plants should be divided late summer/early fall and summer/fall blooming plants are best divided in early spring. Grasses, sedums, hostas, daisies, coneflowers, black eyed Susan, etc.
Click here for our perennial links to find additional info from the University of Minnesota.
A Plea to Help Eradicate Garlic Mustard (Alliaria petiolata)
Ok, last, but not least. Addressing very bad weeds. One in particular comes to mind so I will start with that one. Garlic Mustard’s botanical name is Alliaria petiolate. Such a pretty name for such a troublesome plant. Garlic mustard came from Europe to the US in the 19th century and was first recorded in 1868. I did not even really notice this weed in our area until about 20 years ago, at least not in such disturbing abundance. Now it seems to be everywhere and if left unchecked it will reseed even more broadly. I swear it must have a 100% germination rate! So please get these plants out of your yard, especially before they go to seed. Here is why it is important to try to eradicate invasive plants. Invasive plants are the leading cause of native biodiversity loss. Invasive plant species spread quickly and can displace native plants, prevent native plant growth, and create monocultures. Changes in plant community diversity reduce the quality and quantity of fish and wildlife habitat. Please do your utmost to help eradicate Garlic Mustard and all other invasive plants in your yard!
Click here for Chris’ blog and further information