Growing Perennials from Seed

perennialtrio4222Growing most annuals by seed is straightforward. Nearly every gardener knows to nurture an annual until the last spring frost date. At that time, the tender seedling can join the rest of the hardier clan outside. Not so with perennials, which come prepared by nature to withstand cold. Perennials also may take two seasons to come into flower so the ordinary gardener has to ask the question: “Is this worthwhile?”

Here are a few good reasons. If you crave a sea of columbine, a raft of penstemon or a meadow of coneflowers, you’ll get buckets of plants for the cost of pennies. If you long for a rare plant that isn’t offered in any garden center but sprouts on a seed jacket, you’ll want to take it home. In a few cases, some perennials may be easy to divide, like purple coneflower, but you’ll have to wait a few years for a clump to grow large enough to take advantage of division. That’s another reason to consider seeds.

perennialpenstemons4213And, here’s the final reason: even if some, or many, of your seeds die, you’ve lost less than a dollar and you’ve gained an education. Chances are many will survive and turn out to be hardy garden specimens. Plants grown from seed are especially hardy because they acclimatize to your soil and garden conditions. They do not go through the shock of transplanting.

But here’s the catch. Perennials differ widely in their needs when it comes to planting seeds. And no single approach works for all of them. In some cases, planting from seed is the wrong approach. Are you looking at daylilies, irises or ornamental grasses? Does your perennial grow in a clump at the base that could be divided into small plants? Division would be kinder to these perennials and will renew the mother plant.

Is it a woody shrub, a rose, perhaps? Cuttings would be a better answer for these plants. For a variety of reasons, even professional growers balk at growing woody plants from seed unless there is a pressing reason.

So what you’re left with are the seeds of favorite perennials that have recently come into favor. Prairie coneflowers, Rocky Mountain penstemons, native columbines, salvias, Gazania daisies, blue flax or sunflowers—these are the perennials that gardeners may want to consider planting from seed. Some are easy. And some are not.

perennialhollyhock1299Mike Bone, plant propagator at the Denver Botanic Gardens, lists a few easy perennials to get you started: salvias, Delosperma (hardy iceplant), sunflowers, poppies, Gazania, (only half hardy, so these may not really be considered a perennial), holly hocks and Achillea (yarrows, also easy to divide when large). But he acknowledges that finding information about planting perennials can be tricky. So does Kelly Grummons, from Timberline Gardens, who propagates all kinds of plants for the home gardener. “Information is not that easy to come by,” Kelly says and recommends a book by a Pennsylvania professor: “Seed Germination, Theory and Practice,” by Norman C. Deno. That’s the same book that Mike refers to when it comes to plant propagation for the Denver Gardens. There’s also an informative German website from a perennial grower,

perennialspurpleconeflower1284But what’s an amateur gardener to do if you want to grow one, or just a few perennials? It pays to buy seed from a seller that gives a great deal of information on the packet. You’ll want to know if the seeds germinate in light or darkness, for example. Botanical Interests does just that and Curtis Jones, the president of the Broomfield-based company, says that his seeds have been prepared by the grower to be easy on the home gardener. “The seed companies both stratify and scarify the seed we buy,” he says. That means if the seed needs to be kept in cold conditions for a period of time to germinate, such as Rocky Mountain penstemon, it arrives post cold. If the seed needs to be broken just a bit so that water will penetrate and allow germination, such as lupine seeds, then the grower has done that, too.

perennialslupine4209The exquisite lupine hails from the pea family, which is notorious for being encased in a coating protecting it indefinitely. In the garden, microorganisms will break the coating down. But that requires a very long time. Gardeners often take to rubbing the seeds between two layers of fine sandpaper to scratch tiny holes in the coating.

So, read the seed packet carefully and keep it for future reference. But suppose you already have seed that comes with few instructions, or confusing directions? That takes a new approach, one that must consider the background of the plant. “What time of the year is the plant setting seed?” Mike asks, “If it’s later in the season toward the fall, that’s a clue that they will need stratification (a cold spell). But if it’s early in the season, that’s a clue that those plants germinate right away.” If it’s a crop, like berries, that are eaten by animals, chances are it will require scarification–nature’s protection of the seed as it travels through the digestive tract of critters.

Kelly points out that not all perennials need to be stratified, although plenty of gardening books will tell you to do so. “Prairie and montane penstemons need it. Southwest and high alpine penstemons do not. A rule of thumb is that plants from areas like the tall grass prairie with twenty or more inches of rain don’t need it. But those from the short grass prairie and foothills, do,” he says. Penstemons are abundant in the West, so it’s no wonder that their needs are so varied. Those that are native to the Front Range of Colorado will require a cold spell. Although some gardeners subject all their perennial seeds to a cold spell, Kelly says sometimes the seeds will simply rot from the process if it’s not the right approach.

perennialrudbeckia1279Suppose you have seed that you are quite certain has not been stratified, perhaps the packet instructs you to subject your seeds to a cold spell, or perhaps a neighbor has given you collected seed from a private garden. There’s an easy way to stratify your seeds and check the germination at the same time. It’s a technique that growers have used for years.

Dampen a paper towel and sprinkle seeds across it evenly. Roll up the towel and place it in a plastic bag. Place the bag in the refrigerator (not the freezer). The cool temperatures of the refrigerator will stratify the seeds, which usually require even temperatures of about 40 degrees for four to six weeks. Check the seeds each week by opening the bag. This not only allows you to watch the germination process but permits fresh air to enter the bag. Some circulation of new air is necessary to ward off fungus that may lurk among the seeds. By the time you see a tiny tendril arching from the seed, you’ll know you have complete germination and the seed can be planted in a small pot outside, or even directly in the garden.

perennialsmexicanhat1310If your seeds did not completely germinate, that’s not so uncommon, Mike says. “It’s a misconception that professionals get 100 percent germination,” he says, so don’t be ashamed if you have to buy two packets of seeds to get the bounty you have in mind. Some seeds, like columbine, are wildly fertile for the first three months after they’ve drifted from the mother plant. Then they sink into a deeper dormancy where germination is less spectacular.

“Everyone’s environment is different,” Mike says, so your soil, water and sun exposure will all add to any future success your perennials might face. Propagating plants is like reading a mystery novel, he adds, “you learn so much by the time you reach the end.” And, the extra boon is that if you have any questions about sun exposure, soil or water, you’ll have more than enough plants to experiment with to complete your education.

Photos from top to bottom:

  • Trio of plants: Jupiter’s Beard or Valerian, Centhranthus ruber, a European perennial that grows on bleak cliffs, also used in xeric landscapes and easy to grow from seed. In front is a blue sage (easy to grow), Salvia farinacea and in front the Missouri primrose or Ozark sundrop, easy to grow and drought-tolerant, Oenothera macrocarpa.
  • Penstemons: Rocky Mountain (Penstemon strictus) and Scarlet bugler or iron maiden (Penstemon barbartus), both natives to the foothills of Colorado and require stratification.
  • Hollyhock, Alcea Rosea, easy from seed and often self-seeds. Subject to rust.
  • Purple Coneflower, Echinacea purpurea, a native of the tallgrass prairie, so stratification is not necessary. It does require regular moisture. Also, large clumps can be divided.
  • Lupine hybrids, Lupinus, likes cool weather and moisture, but not humidity. Since it is from the pea family, seed must be scarified. Check with your seed supplier to see if this has been done.
  • Black-eyed Susan or Gloriosa daisy: Rudbeckia, a tallgrass prairie native, so does not need stratification except for the fulgida variety (place seeds in a plastic bag with most towel for two weeks in the refrigerator), but does require regular moisture. Clumps can be divided.
  • Mexican hat coneflower: Ratibida columnifera, also comes in an all yellow variety, native to the shortgrass prairie, so requires stratification, easy to grow, very xeric. Like blue flax seed, it can be sprinkled into the soil in autumn and will come up in the spring. Prefers lean soil.

Recommended Books:

  • “From Seed to Bloom” by Eileen Powell, Storey Communication, Vermont, 1995