As the days begin to warm and the first blooms appear, you can practically hear the rejuvenated gardeners rejoicing as they emerge from their winter hibernation. This is a great time of the year with plants sporting new growth and that familiar smell of soil, created by all those beneficial soil microbes, filling the air. Although there is still a chance for late March snowstorms, there are plenty of days to venture outside, work in the garden and enjoy the beauty around us. Garden time is here!
The challenge of spring is often where to begin! Tidying up and removing the previous year’s growth of perennials and grasses is certainly high on the list. It is best not to complete this task in autumn, as many of our native beneficial insects seek shelter from winter’s wrath in the hollow stems. In addition, many herbaceous plants provide both food and shelter for overwintering birds and their winter forms look great. If perplexed on how much of the growth to remove, study the base of the plant. If the plant is completely herbaceous and has died back to the ground, the stems in turn can be cut as close to the ground as possible. By contrast, some ‘perennials’ are actually woody plants with new growth appearing near the base of the stems. These stems should be cut back to 3-6 inches. Examples are Russian Sage (Perovskia), Bluebeard (Caryopteris), and Lavender (Lavendula). Interestingly, Rosemary (Rosmarinus officinalis) is also a woody plant, but prefers to be shaped by harvesting stems throughout the summer!
Once a plant is cut back, evaluate the health of the crown. If the stems from the previous year are located throughout the entire crown, and the central stems cannot be removed with a gentle tug, the plant is in good condition. However, if the center of the crown does not have any stems or are easily removed as seen below, the crown is in need of division. It is a time-consuming proposition since the plant needs to be dug from the ground, the central area discarded and a piece of the younger outer crown replanted. It is key to note that only a 4-12” portion of the healthy crown needs to be replanted. The balance of the crown can be added to new areas of the garden or simply given to friends! With deeply rooted plants, such as the Cup Plant (Silphium perfoliatum) or False Indigo (Baptisia australis), it is best to leave the plants undisturbed. With their root systems reaching depths of 8-10’, much of the root system and stored carbohydrates will be left behind after division, compromising the plant’s health.
Other spring garden time chores include the annual mulching of beds and a biennial soil test. Soil tests ensure the pH and nutrient availability is appropriate and provide information on any necessary corrective measures. Often, people apply fertilizer when none is necessary, promoting excessive and often weaker plant growth. It also promotes the need for more frequent, back-breaking plant division! Mulch is beneficial for reducing weeds and retaining soil moisture. One of my favorite mulches is shredded leaves. It is best made the previous fall through weekly chopping of fallen foliage with a lawnmower. Shredded leaves allow water to more readily soak into the ground and provides habitat for beneficial insects. If you prefer shredded wood and 1-2” remain from last year, only add 1-2″ of new mulch; mulch in excess of 3-4” deep can harm plants through shallow root production. Also, avoid creating mulch volcanoes around trees. It has become an epidemic in some neighborhoods and actually harms the tree by retaining moisture adjacent to the bark.
Lastly, while mulching make certain to watch for emerging bulbs. An often neglected group, bulbs add great color to the early spring and autumn garden. They will often naturalize and although the declining foliage is unsightly, it should be allowed to turn yellow before removal, ensuring ample blooms for years to come! Yes, the new garden time season has begun, and although there is always more to do than time allows, find time to relax and enjoy the fruits of your accomplishments!
*A longtime proponent of unusual and fun plants, Bruce Crawford is the State Program Leader for Home and Public Horticulture and a member of the NJNLA board. He is also an instructor in Landscape Architecture at Rutgers University. A graduate of Bucknell University, Bruce also lectures frequently and has yet to find a plant that he does not like!