Lupins are a beautiful plant to grow from seed. One of the main reasons for this is that they tend to look more like small Lupin plants than seedlings. Yes, even when they are only 2-3 inches tall they have those funky leaves which give them so much character. However, the flowers will come later on in the season.
From our personal gardening perspective, we attempt to be as space conscious, power conscious and feeding conscious as possible to get the maximum yield without extra effort and waste. Thus, this post about growing Lupins from seed seems to be unlike any of the others we have read, especially the initial pot size. We will get to that in a minute.
After a delivery of Lupin seeds in the winter, we can keep them in a cold, dry place until we want to use them. Then, we can transplant a single seed into a 72-cell flat with 4-inch dome that is placed on top of a heat pad. If we do have a heat pad, we can continue the initial germination, but we do not want to be in a cold climate. We could bring these into a room temperature setting and wait for germination too before we move them under lights, but, buying and using a heat pad works every time.
We do not need light during germination. Read about starting seeds that do not require light is a guide to raising vegetable seedlings which can easily be applied to Lupins as well. Since all veggies and flowers will germinate at various times, that makes time the changing variable.
Finally, we wait until some germinate. This can take a few days to a few weeks. When the first seedlings emerge and are starting to stretch(but not too much), we turn on a single led light and still use the dome.
After more start to grow, we shed the dome, lower the lights and mist a few times per day with a pump sprayer. At this time, the tops of the cells where the seeds are placed will dry more quickly, for the obvious reason that the leds emit a little heat. This led heat also eliminates the need for the heat pad, but we can still use it at our discretion or use it during the hours of darkness.
A typical light schedule is 18 hours on/ 6 hours off, but, we could run them all day and night during the germination times. and run them less(or continue at 24 hours/day) after many plants have sprouted.
Now, after 4 weeks since we placed that tray on top of a heat mat, we can transplant our seedlings from 72-cell flat(s) to 3, 31/2 or 4-inch pots.
After Lupins are a couple weeks old, we can use a mild 1/4 strength fertilizer. Two to three feedings and alternate waterings will keep them healthy until they are moved to bigger pots.
In our case, we started them around March 5 for an April 4 transplant. If we started them in 3.5 inch pots, that is the difference between 72 plants under 2 lights and 1 heat mat vs 288 plants…..big difference here.
After our transplant, we can continue to grow under lights or move plants into a coldframe, greenhouse, or tunnel if the weather permits. During this time, we like to keep a steady eye on the 14 day forecast to know what we could be receiving for night temperatures.
If the weather looks okay and semi-frost free, no extra heat will be required outdoors. But, if frost nights are possible, we can place them onto a sand-filled tray that has a heat cable in the middle. If the cable is spaced at 8cm(3 inches) or so it will provide even heat for the moist sand. Fine, river sand works well.
A heated bed will increase the temp a few degrees. For example, in our heated bed, the temp on top will be at 6 degrees Celsius(43 degrees F) while the temp in air at same elevation in the greenhouse is 0 degrees F(32 degrees F).
Although 6 degrees is a nice jump and puts us well out of cold danger, we can place a blanket on top of the table about 1 foot over the seedlings. This will trap the heat and keep them even warmer if temperatures fall.
Growing Lupins from seed is fun, rewarding and a huge savings for the pocketbook. They are easy to grow. Even though they can grow a few inches in a month, they are low maintenance seedlings that do not intake copious amounts of water, nor create an excess root system in four weeks.
If we simply remember the 4-week rule, we can have an abundance of Lupins any year we choose to grow them from seed.