It’s fun to grow perennials from seed. And besides, it’s bright! You can have more of them and a far greater variety at a meager cost. Of course, raising perennials from seed takes a little more care than it does to set a purchased plant in the ground. But to a natural gardener, that too conies under the heading of fun.
The beginner will probably choose seeds of perennials that he already knows, which is what he should do. When he has succeeded, he may try more unusual kinds, moving by easy stages from the known to the unknown—adventuring as he grows in experience, skill, and horticultural knowledge.
Some seeds require or prefer a reasonably long exposure to low soil temperature. These kinds may be started in early spring while the ground is still cool enough to make conditions suitable. When grown from seed, lilies quite definitely fall into this group.
Other perennials with similar germination requirements or preferences (there is a difference) are irises, liatris, dictaninus, aconitunt, helleborus, penstenum, primula, saxifraga, hardy geranium, trollius, eremurus, hardy chrysanthemum, azalea, anemone, alstroemeria, allium and, to a somewhat lesser degree, also armeria, gentian, and aquilegia.
Low Soil Temperature Needed?
Throughout the group, there is a variation in the degree of low soil temperature needed. Hellehorus, dictamnus, and aconituni will grow only if temperatures remain low for some weeks after sowing, while gentian, armeria, and aquilegia will often grow well sowings are made as late as June or, in the case of aquilegia, even well into summer.
But, just the same, these seem to prefer the cooler weather of early spring, and they get off to a better start when sown so they can take advantage of it. The other species listed grade their degree of preference for cool soil from helleborus, which requires a long period of cool soil to aquilegia.
Early spring sowings may be made in a cold frame, but good results may also be had from seeds sown directly in open ground seedbeds. If care is used, open ground sowings may give better results. The advantage of a cold frame is the protection it provides from hard, beating, washing rains—a point may be of great importance in some parts of the country.
It is usually easier to shade the planting with a frame when necessary, although this is seldom required with early spring sowings. A possible disadvantage is that the glass is likely to be left on when it should be off, thus raising air and soil temperatures beyond what is desired and perhaps drying out the seedbed.
Sowing Seeds In An Open Ground
For open ground sowing, it is not advisable to plant the seed where the perennials are finally to stand. That method is likely to result only in loss of roots, tempers, and confidence in sources of supply. The best way is to prepare a seedbed in some sheltered corner of the garden that is not shaded by trees; a bed 30″ inches wide is easy to work.
The spot should be well-spaded and broken up, so the soil is acceptable without lumps. Either compost or manure is then mixed in thoroughly. Commercial pulverized sheep or cow manure will do if another waste is unavailable.
If your soil is on the lean side, or if the quantity of compost or stable manure is small, a light application of any commercial fertilizer may also be made, but be sure not to overdo it. Too much can burn the roots of your seedlings.
Soil fertility has little effect on seed germination, but it depends on how vigorously the seedlings grow afterward. On the other hand, the texture or condition of the soil may have much to do with the percentage and speed of germination.
Soil should be friable so that it will barely hold together when a damp handful, not a soaked one, is squeezed. Neither a heavy, sticky clay soil nor a very light loam will give just the right conditions for a seedbed.
Some seeds will germinate well in such soils. Still, the most satisfactory returns from a wider variety of sources will come in soil reasonably good in texture and fertility.
Soil Good Texture and Fertility Give Best Seed Germination
Applications of compost, well mixed in, make a light soil heavier and a heavy soil more lightweight and more workable. Compost adds humus, directly usable plant food, and a certain amount of fiber that prevents packing and crusting.
This increases the water-holding capacity of the soil and, paradoxically, by loosening naturally heavy soils and promoting better drainage after rains.
All these returns will also come from the use of well-rotted stable manure. Although it adds little fertility, peat will do much the same work. Some commercial peats are acidic, but a little time will correct this. Many of the commercial peats will require no correction when used moderately.
Be very sure the soil is deeply worked and the fertilizer Well mixed with it. If one wishes, the bed may be slightly raised above the garden surface, but this is not necessary unless surface drainage is poor.
Sowing Seeds in Pots and Pans
When seeds are sown in pots or seed pans under glass, the seeds are usually broadcast or scattered over the surface, but sowings made in larger containers, such as flats or seedboxes, will be more easily handled if sown in rows. Our work uses flats of 14” by 20″ inch surface dimensions, sowing seeds across the flat, usually nine or sometimes ten rows to the flat.
If seeds are sown somewhat thinly in the row, most of the hardy perennials can be left, if desired, for one full year of growth in the flat, from sowings so spaced. Be sure that a flat of 4″ inch depth is used if you plan on leaving perennials for an entire year in the flat.
The 4″ inch soil depth is needed to ensure proper root growth. Flats 3″ inches deep are satisfactory for starting annual flowers or solid and quick-growing perennials, such as hollyhock or delphinium, which are left in the flat for only a few weeks or months.
So far as spring sowings of perennials are concerned, the advantages of flats over direct sowing in the soil of cold frames are not significant. Still, there may be some slight advantage to those with little spare time, for sowings in fiats can be made under shelter on rainy days or during the evening, the flats later being placed in the cold-frame.
Plants That Are Grown in Flats
Also, plants grown in flats are likely to be more complicated and have a better, more dense growth of roots than those produced from direct sowings in the soil of frames. This gives them an advantage when transplanted, for there will be less shock and retardation due to the moving.
When sowings are made directly in the soil of cold frames or open ground seedbeds, it is usual to space the seedling rows about 4 inches apart, the rows running across the beds. A 4″ inch spacing allows room for using a weeder between the rows and gives space for good quick growth of the seedlings.
The actual sowing of seed may be from the corner of an envelope, shaking or tapping the envelope gently to give even flow. There are also several small seed-sowing gadgets on the market that work well in providing even seed distribution.
The experienced gardener, though, is likely to use only his fingers. In finger-sowing, a certain skill can hardly be acquired through directions, but each person will naturally work out their own best system with the tune.
The main thing is, do not sow too thickly or cover too profoundly. There can be no rule of thumb, for the proper depth is a case of gauging and balancing soil, seed, season, and weather. For most seeds in good friable soil, a depth of perhaps three times the seed’s diameter will work outright, but in light soils, the depth may be more significant; in heavy soils, less.
Maybe the best way to open rows is by using a planting stick, just a thin narrow board or even a lath, sharpened on one edge and pressed into the soil to open a furrow of even depth. Be sure the row is well firmed down after sowing, so the soil particles will directly contact the seeds.
Don’t be too impatient about germination. Certain seeds will come up quickly and strongly within a few days after sowing, but others may require several weeks, a few kinds even months, before germination should be expected.
In general, the types that like cool soil conditions and need early sowing will take longer by their natures than those upon which late spring or summer sowing is suggested, but there are exceptions. Of course, if you sow a heat-loving kind in early spring when you should be sowing only those that prefer cool soil, you must expect delayed germination or perhaps no germination at all.
Spring Watering Is Necessary
Watering an open ground seedbed is not often necessary, so far as early sowings are concerned, but adequate watering must be done in a spring drought. Effective watering is the kind that soaks the dry upper layers of the soil down fur enough so that contact is made with the under the soil, which is still naturally moist.
Of course, the watering must be done slowly and carefully enough so that the soil covering the seeds is not washed away. A surface wetting will not do. Don’t water at all unless you can do an excellent job. Several waterings may be needed with late spring and summer sowings in dry seasons.
Early sown beds will require shading only in years of swift hot springs, but summer sowings will usually be the better for a bit of shade. A lath screen placed a foot or more above the bed is perhaps most effective, a screen with spaces between the laths equal to their width. Single layers of burlap or heavy cheesecloth tacked to frames are sometimes used for seedbed shading.
The function of the shade is to temper the heat of the sun, thus cooling the soil a bit. Even the heat-loving seeds can have too much heat. The shade also helps to conserve moisture by lessening evaporation, and it will tend to keep down crabgrass in case seeds of that weed are in the soil.
The shading helps both before germination and afterward during the early growth of the seedlings, but when the seedlings are once well established and have struck out with a good root system, the shading may well be removed.
Also, during any considerable cold, cloudy or rainy weather, either before or after germination, lake off all shades. Shades left on during that kind of weather are likely to increase damage from molds, fungi, or bacterial rots, and they may give conditions favorable to the growth of moss. Scanty germination of seeds is likely in any bed once mussed over.
Keep The Seedbed Free of Weeds
Catch the weeds when they are small, and do the catching often. Don’t let weeds steal your seedlings’ fertility, moisture, and space. Weeding can begin before the seedlings germinate. Indeed it should start long before your seeds are sown, a year or more before, for the seedbed should be put in a position that has been made relatively free of weeds.
The seedbed can be sterilized two weeks before sowing with chloropicrin or tear gas if one wants to carry this further. This will destroy most kinds of weed seeds but unfortunately not all kinds, and it will also kill slugs, grubs, wireworms, and the like, and perhaps lessen the chances of damage from fungous diseases. Chloropicrin is available for horticultural use under various trade names.
Planting Perennials at Different Times of the Year
Sowing perennial seeds of different kinds can be a continuous operation throughout the year, except for the period from late September into early November. By the middle of November, sowings of the kinds that require a long period of low soil temperatures may begin throughout the winter and into early spring with those that need only a shorter low soil temperature.
By late spring, the range of perennial species that should or may be sown has significantly widened. In May and early June, one may still sow aquilegia, allium, armeria, chrysopsis, hardy geranium, and even liatris, gentian, and the easier primulas, and along with these the very many additional kinds for which late spring is, in the year of average weather, the ideal sowing season.
Try late spring sowing for alyssum, arabis, aubrieta, polemonium, erodium, asclepias, baptisia, titermopsis, callirhoe, potentilla, anthericum, tradescantia, cassia, cerastium, thalictrum, viola, elsholtzia, genii’. mertensia, gillenia, isatis, silene, lysimachia and lythrum.
These are but a few of many, and while May (and early June) is their preferred sowing season, most of them may still be sown in summer with good results providing attention is paid to shading. They join the rather large group of perennials that quite definitely desire summer sowing.
Perennials sown in early or late spring will be large enough for transplanting to their more or less permanent positions by early autumn. Still, they can remain in the seedbed without damage until the following spring if that happens to be a more convenient season for handling them.
Large perennials may be moved with good results until quite late in autumn, but first-year seedlings that have not made deep roots should be transplanted early enough to still be a few weeks of good growing weather before the ground freezes to root depth. Give the young plants a chance to get their root anchors down in the new position. It will save a lot of winter damage.
You can have summer damage, too. This happened when the plants were moved too early while the days were still hot. Then the sun pumps moisture out of the transplanted seedlings faster than the root system can replace it, for it is necessarily damaged and shortened in transplanting.
In Philadelphia, it is usually safe to move young, spring-sown perennials from mid-September to late October, but that won’t necessarily hold for other regions or even here. Don’t be bound by dates in this or any other garden operation.
Instead, in planning your work, judging by the weather of individual tile season in your particular area. Summer-sown seedlings, in any case, and rarely large enough for safe autumn moving. Better defer transplanting them until the following spring, fairly early then, though, if you want a reasonably good flower display that season.
When late autumn comes, and the ground begins to freeze, it is wise to protect any beds containing seedling perennials with generous mulching of straw, salt hay, corn stalks, evergreen boughs, or other coarse litter that will not mat down.
The object of this protection is to keep the ground frozen and prevent the destruction of seedlings by heaving. It is alternate freezing and thawing that damages young plants that have not yet struck down strong anchoring roots below the frost line.
This freezing and thawing process, actually an alternate expansion and contraction of the soil, gradually works the plants, seeds, and all, out above the surface where the sun and cold wind will complete the destruction.
Perennials with relatively large smooth short roots are most likely to be injured by winter heaving. This includes platycodon, eremurus, hibiscus, scutelaria, callirhoe, and aquilegia. These full winter hardy once established and beyond the seedling stage, not needing any protection then. Loose mulching that will catch the snow is most likely to be satisfactory.
Leaves are riot too good, for they often mat down as they decay to a soggy mass that may cause rotting of plant crowns, but leaves of poplars, buttonwood, and tulip-tree (Liriodentiron) are less likely to cause damage than are those of oak or maple. Remember that winter mulch protection will harm if it is left on in spring after new growth has started.
44659 by Rex D. Pearce