Handbook of Plant and Crop Physiology

GERMINATION AND EMERGENCE 91

Chill 5°C 7 days

12–18 10–16 8–15 10–15 5–10

Verbena

hybrida

Garden verbenaVerbenaceae

Veronica

spp.

SpeedwellScrophulariaceae

Viola

spp.

Pansy, VioletsViolaceae

Waldsteinia

spp.

Barren-strawberryRosaceae

Xeranthemum anuum

ImmortelleAsteraceae

Zinnia

spp.

ZinniaAsteracea

A P P P A A

18

18–21 18–21 21–24

22

24–27

10–13 7–10

10

15–16

18 21

D L D

D or L

Germination can be slow and

erratic. Keep germinatingmedium on the dry side.Total darkness necessaryuntil germinationcompleted. Apply fungicidebefore sowing to preventdamping-off disease.

Reduce night temp. of

medium by 3°C for bestgermination.

Reduce night temp. of

medium immediately aftergermination. Applyfungicide before sowing toprevent damping offdisease.

Germination is erratic.Difficult to transplant. Best

sown directly to garden orcontainer.

Difficult to transplant. Best

sown directly to garden orcontainer.

1. The list is limited to genera and species grown primarily in North America from seeds for their ornamental value. References

used for the compilation of the table: 27–34.

2. If seeds require light for germination, maintain adequate moisture around the seeds during the germination period by a mist s

ystem, by careful watering with a fine spray, by use of a plas-

tic cover over seed trays, or by watering from the bottom. Otherwise, cover the seed to a depth at least twice its size with ve

rmiculite or sowing medium to ensure adequate moisture is

provided.

Caution

: plastic covers cause heat buildup which, if allowed to reach high levels, could be detrimental to seeds.

3. Low temperature, such as that in a refrigerator, increases the longevity of most species of seed. Unless otherwise indicated,

store dry in the original sealed packet or in a tightly closed

plastic bag or sealed container. Silica gel or other hygroscopic substances may be added to resealed packages or containers to

keep humidity low.

4. Freshly harvested (fresh) seeds of many herbaceous species will germinate if sown right away. The same seeds produced from a

seed house or garden center have been stored for a pe-

riod of time and may require chilling (stratification). Chilling temperature (near freezing to 5

C) in a refrigerator or cold room will usually suffice. However, freezing temperature (



10



to



20

C) such as in a household freezer is often recommended. Seeds may be frozen before or after sowing.

5. Fall sowing of herbaceous perennial seeds in outdoor beds or in flats or containers kept outdoors during the winter will sati

sfy their chilling (cold stratification) requirement to germinate

the following spring. This practice may also replace a need for warm stratification or for scarification. Alternatively, germin

ation can be scheduled to occur at any time after chilling seeds

in a refrigerator.

6. Reducing the temperature of the germinating media at night by about 3

C may enhance germination of many herbaceous species. Gradually reducing the temperature during the post-

transplant stage allows the development of short, sturdy plants, which are usually more desirable.