Even though they do not form woody stems, proper planting depth is still important when dealing with herbaceous perennials. Unlike trees, perennials have a somewhat limited root zone. Therefore, you will generally be amending the soil with additional organic matter or other amendments to make it better for plant growth.

A. Planting Bare Root Herbaceous Perennials - Often, plants sent through the mail or UPS will come bare root. This is perfectly fine as long as you keep them in a cool location or in the refrigerator  if there will be a delay in planting them. Unlike shrubs and trees, perennials are commonly sent bare root with their foliage either intact or it may be cut off. By keeping them cool and moist, they should be o.k.

In the garden, simply dig a hole large enough for the depth and spread of the root mass. Spread the roots out a bit and fill the hole with the previously amended soil you took out. Be sure to water them in as soon as possible to eliminate air pockets in the soil which may dry out the roots.

B. Planting Container Grown Herbaceous Perennials - Herbaceous perennials that come in plastic containers from the nursery may be treated like any other container grown plant. Remove the container and check the root mass. If it is a solid mat of roots or some roots are circling, be sure to cut them with a knife or pruners. This will help the plant to spread its roots out into the soil in a more natural configuration.

Dig a hole the same depth as the container, spread the untangled or cut roots out as you place them in the hole and then cover them with soil. Water the area thoroughly after planting to help the soil settle and remove any air pockets.

Be sure to follow the spacing guidelines on the container label. This will allow the plants to grow to their mature size without crowding others nearby.

We are talking here about that huge category of plants that are commonly called "bedding plants" in the nursery industry. In a botanical sense, some of these are true annuals that complete their life cycle in one year and then die. However, a big percentage of the plants are really what are called tender perennials. That is, in their native environment of the tropics or sub-tropics, these plants would live more than two years. But, they cannot survive in areas with cold winter temperatures so they are treated as "annuals" since they will die when exposed to frosts.

Anyway, planting annuals is just like planting container grown perennials. Remove the container and check the root mass. If it is a solid mat of roots or some are circling, be sure to cut them with a knife or pruners. This will help the plant to spread its roots out into a more natural configuration. Dig a hole the same depth as the height of the container, spread the roots out as you place them in the hole and the cover them with soil. Water the area to help the soil settle and remove any air pockets.

Be sure to follow the spacing guidelines on the plant label. This will allow the plants to expand and fill a certain area to allow for the bed or border to fill in over the summer season.

The exception to the spacing rule will apply when you are putting annuals or perennials in containers. There, you will generally want to crowd them in so that the pots overflow and give a great display quickly.

C. Planting Herbaceous Perennials from Seed - Certainly perennials may be planted from seed but there are a couple of extra factors to consider over planting annuals. These would include:

1. Seed Treatments - Annuals are almost all designed to germinate once the soil gets to a certain temperature. Many perennials have developed some different mechanisms to help assure their survival in a wide range of often unfriendly environments. These fall into two basic categories: a) Scarification for hard seeds and b) Stratification which is a cold, moist treatment.
   
   

2. Hybrid Plants - We usually get our annual seeds in a packet from the plant breeders and are assured that what we plant will be what we anticipate. However, if you save seeds from perennials in your garden, the outcome is not so certain. Many of the plants that are named cultivars may not come true to seed in the next generation. These plants are sometimes the results of specific cross breeding programs and the seeds you collect are probably crossed with some different cultivars growing nearby. The plants resulting from such seeds will often not resemble those from which the seeds were harvested.
   
   Some perennials, however, reproduce quite nicely from seed and the seedlings will be just like the mother plants. The key is for you, as the gardener, to do some research into the specific type of perennials you want to start from seed. Find out which ones come true from seed and which ones do not.