How Late Can Cool-Season Perennial Forages Be Planted?

Spring is a traditional and popular time in Pennsylvania to plant forages. However, wet soil conditions and unpredictable weather often make this practice difficult. Many growers ask, "When is it too late to plant?" or "If I can't plant my cool-season forages this spring, what can I do?"

When is it Too Late to Plant?

This answer depends on the weather as we move into the heat of summer. We can rely on what we know about how cool-season forages are established. Cool-season grasses will begin to grow when soil temperatures reach 40-45°F, reach their optimum growth when temperatures are between 60 and 75°F, and decline in growth as temperatures continue to increase in the summer months. Cooler night temperatures can help with development on hotter days, but eventually, cool-season grasses will go dormant until the fall, when temperatures begin to recede.

To start answering the question "When is too late to plant?" we will need to make a couple of assumptions,

• First- we will get adequate moisture; not too much or too little, but just the right amount for germination and initial growth. 
• Second- the temperatures will remain consistent with the state averages and not be unseasonably warm or cool.
• Third- day temperatures above 75°F can be tolerated if the lows are less than 60°F.
• Fourth- stands will be established a minimum of six weeks before the temperatures outlined in assumption three are reached, sending the stands into summer dormancy.

Yes, many things are working against us, but this can make spring seedings challenging.

State weather data tells us that certain parts of the state will have different cut-off dates. Historical weather data shows that on average, highs are greater than 75°, and lows are greater than 60°. See Table 1. This climate data shows that it is safe for some areas of the state to plant until mid-May, while late April represents the closing date for others.

Information from the PA State Climatologist

This should not be used to make all your decisions, nor by any means is this saying, "Anything after this date will fail," but it is evident that the risk associated with these plantings does increase after these dates.

What do You do if you can't Spring Plant?

Since this is a spring-seeded forage, the expectation should be low for getting more than one cut toward the end of the growing season. Meaning, yield loss may be more evident in the next growing season when attempting to get multiple cuttings. However, if hay or pasture is in short supply without this planting, use a summer annual, like sorghum-sudangrass or millet, followed by a fall-seeded cool-season perennial to reduce a forage shortage this summer. Planting a cool-season perennial in late summer or fall will allow the stand more time to catch up and return to productivity rather than waiting for the subsequent spring to try again.

Read Alternative Forages for Spring and Summer Planting for more information on alternative forages. For information related to fall forage establishment, read Fall Forage Establishment and No-till Forage Establishment.