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Germination Strategy at Noelridge Greenhouse

Starting as early as January, we are busy sowing seeds. We grow over 500 varieties of ornamental annuals at the Noelridge Greenhouse and Gardens. Depending on the species, the germination strategy can vary greatly.

First, we select the proper growing container; this can be various sizes of pots or a germination flat, depending on the number of seeds. Next, we prepare the growing media, for this we use a sterile soilless seed starting mixture made out of peat moss, vermiculite and perlite. To prepare we add enough water to the mixture so that the mixture is evenly moist but not soaking wet. A good rule of thumb is when you grab a handful of mixture and squeeze it, no water will come out but instead the mixture will stay in a solid formation.

After preparing the growing media we fill up the container, we can use a weight to slightly compress the mixture but not too much. We will then add the seeds to the container, being careful to place the seeds evenly apart across the surface of the container. Depending on the species, some seeds that are really tiny need light in order to germinate, however other species require darkness to germinate. For the seeds that require darkness, we use a flour sifter to lightly cover the seeds with vermiculite.

Once the seeds are in the containers we lightly water them with a seedling nozzle attached to a hose. We then use a glass lid to cover the pot to keep in humidity, and place the containers underneath a grow light. Germination times can vary dramatically, some seeds like the species Salvia guarantica (Black and Blue Salvia) can germinate in a matter of days while other seeds like the species Carex buchananii (Red Rooster Sedge) can take weeks to germinate. Even individual seeds of the same species can be immensely different, for example the species Optunia humifusa (Eastern Prickly Pear Cactus) can take anywhere from five days to up to six months to germinate!

The seedlings will stay under the row light until they emerge with their cotyledon leaves and hit the glass ceiling. All flowering plant species are either Dicots (Dicotyledons) or Monocots (Monocotyledon). Dicots (Forbs) have two cotyledon (embryonic) leaves when they first germinate, while Monocots (Grasses, Sedges, etc.) only have one cotyledon leaf. The cotyledon leaves have all evolved to look the same. These are the first leaves that form when the seedling germinates.

After the seedling continues to mature the next leaf is called a true leaf. The true leaf is unique to each species and will be a miniature version of its adult leaves. Once two true leaves are well pronounced, with the help from our volunteers (The Friends of Noelridge) we transplant the seedlings into plant plug grow trays. These seedlings will grow at Noelridge Greenhouse for several months before they are planted around the city including the airport, golf courses, various parks, downtown and of course the gardens at Noelridge.

Currently at the Noelridge Greenhouse we are also growing over 100 species of Native Tallgrass Prairie Plants, many of which require some form of seed stratification. This can include scarification, which is the action of weakening the seed coating through the use of boiling water or from scratching the seed with sand paper. Another form of stratification is using temperature change to force the seed to activate by mimicking the natural change in seasons. Some species only require one of these tactics for example Desmanthus illinoensis (Illinois Bundle Flower) of the Fabaceae (Legume) family requires stratification but does not require any cold treatment. On the other hand Penstemon calycosus (Calico Beardtongue) of the Scrophulariaceae (Figwort) family requires 30 days of cold treatment (32 - 38° F) to start the germination process but no scarification is necessary. Some species require both scarification and stratification for example Callirhoe involucrata (Purple Poppy Mallow) of the Malvaceae (Mallows) family requires scarification through the use of boiling water to mimic intense heat caused by wildfires, it then also requires a cold period to mimic the season of winter. Both of these steps are crucial for the seed to begin its germination process.

Stratification process can be even more complex still, for example Arisaema triphyllum (Jack in the Pulpit) of the Araceae (Aroid) family which is a monocotyledon requires a cold period of 60 days followed by a warm period of 60 days followed by another cold period of 60 days to mimic two winters. Come in and take a look, we are open Monday through Friday from 7:00 am to 3:30 pm except for Thursdays which we are open from 7:00 am to Noon.

  Cedar Rapids, Iowa, 101 First Street SE

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