Spiraea alba

PLANTING INFO:

Planting plugs:

We consider plugs ready to ship when the plants’ roots have filled the entire liner cell and the plants can easily be pulled out. In some cases you will have to go about it gently, wiggling the plant by the crown, and possibly squeezing the bottom of the liner to compress the growing medium and release the roots. Other times, the plants will appear to be root bound. They are not in the traditional sense. The plants are healthy but they have used up all the growing medium available to them. Plugs are at an aggressive stage of growth. As soon as planted the roots will immediately expand into your native soil. They establish faster than plants in larger containers, because they don’t have the luxury of a lot of growing media that can inhibit the roots from venturing outside of their comfort zone.

We are not going to address area preparation because the process can be complex and is always site-specific. However, as a rule, we recommend disturbing the soil as little as possible, and we do not recommend amending the soil. If you chose the right plant for the right conditions they will thrive. Any disturbance and amendments will only encourage weeds to emerge that never had a chance to do so before.

Installing plugs cannot be easier: dig a hole large enough for the roots to fit snugly inside, then water them in to eliminate air gaps. We recommend using a soil knife, sometimes referred to as hori hori, or a drill-adapted auger if it’s a large installation. If you use an auger, you will need a powerful drill. Depending on the size of the project and the type of soil, the process can be beyond what an average drill will bear. Mulching is recommended after installation to help keep weeds down while the plants establish. Be sure to keep it away from the crown of the plants. For large projects, you may want to mulch the area before planting, rather than tiptoeing through it after the fact. As a side note: if you are installing plugs in the fall, you might want to plant them so that the crown is about ¾” lower than the surrounding soil. The winter’s freeze/thaw cycles can push plugs out if the roots did not have enough time to establish and anchor them in.

Starting and planting seed:

Direct sowing:

For most forbs - also referenced as flowering perennials - the best time to sow is during fall and winter to expose seeds to the natural cycles of alternating cold, moist and warmer weather that they have evolved to require in order to germinate. There are of course some exceptions, and some species will germinate under warm conditions regardless of having first been exposed to a cold period. Most grasses fall under this category. There are also species that will require a couple of years of cycling temperatures in order to germinate, so it is important to understand each species’ requirements and manage one’s expectations accordingly.

Soil preparation:

Like any type of garden, a well-prepared soil makes the difference. Remove any large debris. Kill and remove any grass sod. Till and rake the soil until an even surface is achieved. Starting from seed is the most cost effective way to start your native planting; however, it requires time and patience. Most species we carry are perennials, meaning they will come back each spring for many years. As perennials, the plants will grow slowly and may take several years to mature and flower.

Planting seeds:

Planting these seeds is very similar to planting other types of seeds: small seeds are planted very shallow and large seeds are planted deeper. A good rule of thumb is to plant the seed the same depth as the seed’s thickness. For example, a 1/16” thick seed is planted 1/16” deep. A light straw mulch is recommended for late fall seedings. There are also some seeds that, either due to their small size or light requirements to germinate, should only be surface sown and kept clear of any coverings.

Sowing seed can also be a good way to add diversity to an existing planting. Should that be your application, soil preparation is not necessary because you will be mimicking the process by which plants naturally spread in established environments. To improve germination rates, winter sowing is very effective especially right before a snow event. The snow will hide the seeds from foraging birds and mammals, provide the steady moisture needed to trigger germination, and will help work the seeds down to the soil as it melts.

Once plants are established they will require minimal maintenance. Remove any large weeds, especially if they flower and set seed. If weeds become a problem in seedings you can mow during the first two years to a height of 10-12 inches. This will benefit your perennial plants by providing more sunshine.

Starting your seeds indoors:

If you want to have more control over the germination process and planting - or if you want to start your seed in spring or summer before they are exposed to freeze/thaw cycles - you will want to mimic natural conditions by using a process known as cold/moist stratification:

There are several methods that can be used to stratify seed. For large quantities, the recommended method is to mix the seed into a moist, sterile medium such as sand, perlite, vermiculite, or a combination of the 3, and then refrigerate as required. For smaller quantities, spreading the seeds evenly between moist sheets of paper towels and refrigerating them in a resealable plastic bag will do just fine. You should check regularly to verify that the medium, or paper towels, has not dried out. You also need to check for any signs of germination that might occur before the recommended stratification period has elapsed. Should that occur, or if you have met the recommended stratification period, you should remove the seeds and plant them immediately in your preferred potting medium. Use the previously mentioned guidelines for determining seed depth.

Some seeds have especially hard protective coatings. In nature, those get broken down by soil abrasion or by passing through an animal or bird’s digestive tract. In addition to stratification, those seeds will require scarification to improve germination rates. Several methods can be used to achieve this. Gently rubbing the seeds between two sheets of fine sandpaper is one of them. Another method is to mimic exposure to digestive enzymes and to soak the seeds for 24 hours in some diluted tea.

If you do start your seed indoors, we recommend timing the process so that germination will occur after the last chance of frost. That way you can move your seedlings outside without having to manage appropriate indoor light exposures.