Spring Flower bulbs need a good, long winter’s sleep. Like some people we know, if they wake up before they are fully rested, they get kind of cranky, and then they don’t bloom well at all.
Freeze/Thaw Cycle Can Damage Spring Flowers
What happens during a mild winter is that the soil stays too warm. This means that the bulbs begin to come out of dormancy early. They will start to grow, and once the tips emerge above the soil line, they are subject to freezing if the temperatures dip back below freezing, which is usually what happens. After the bulbs have emerged, they freeze and then don’t bloom at all, or if they do it’s a very poor display.
Another reason bulbs can bloom too early or freeze in the ground is that the bulbs are not planted deep enough. They may have been deep enough when you planted them, but as the soil goes through the freezing and thawing process, the bulbs can be pushed toward the surface. One way to keep your flower bulbs sleeping longer, which will protect them from freezing, is to mulch the bed.
To do this, in the fall, apply a 3-4” layer of well-composted mulch on the top of the flower bed. This layer of mulch will do a couple of things. It will maintain the higher moisture content in the soil and this is good as long as the soil isn’t already too soggy. Well-composted mulch also adds valuable organic matter to the planting bed which makes a great natural fertilizer.
Mulch Can Keep Ground Thawed (And Frozen)
A 3-4” layer of mulch also acts as an insulator that will keep the soil from freezing for a while. This is good because you don’t want the bulbs going through a series of short cycles of freezing and thawing. In Fall and Winter when the temperatures drop below freezing and stay there for a while, the soil will slowly eventually freeze. During the spring the mulch works in reverse and keeps the soil from thawing too early. Keeping it in a frozen state is good because the bulbs remain dormant for a longer time.
When the bulbs finally do wake up it is springtime, and hopefully by the time the shoots emerge from the ground the danger of a hard freeze is past and they will not be damaged. If you can keep the shoots and bulbs from freezing after they start growing, they will flower beautifully. The extra organic matter will help to nourish the bulbs when they are done blooming, and the cycle starts all over again.
If you plan your garden carefully, it is possible to have it bloom all summer and into the fall. So look carefully at when each bulb is supposed to bloom when designing your garden. We also plant annual flowers in the same beds as our spring bulbs. By the time the danger of frost is past and it’s time to plant the annuals, the top of the bulbs have died back and are ready to be removed. The mulch that is added in the fall also helps to nourish the annual flowers, as well as improve the soil permanently. Any time you add well-composted organic matter to your planting beds, it is going to produce multiple benefits. The keywords here are “well composted”. Using fresh material instead of well-composted material will not produce the desired effect and could damage your plants. Always use properly composted material.
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